INTRODUCTIONAcute respiratory infections (ARIs) continue to represent one of the most pervasive public health challenges globally, accounting for substantial morbidity, hospitalization, and mortality…
INTRODUCTION
Acute respiratory infections (ARIs) continue to represent one of the most pervasive public health challenges globally, accounting for substantial morbidity, hospitalization, and mortality across all age groups. According to the World Health Organization, ARIs are responsible for nearly 20% of global deaths in children under five years of age, with a rising burden among adults, particularly those with underlying chronic diseases and compromised immunity. In low- and middle-income countries, frequent viral and bacterial respiratory infections further strain healthcare resources and lead to significant socioeconomic consequences.
Over the past two decades, increasing attention has been directed toward the non-skeletal actions of vitamin D, particularly its immunomodulatory potential in preventing infectious diseases. Vitamin D is a secosteroid hormone synthesized in the skin upon ultraviolet B radiation exposure and obtained from dietary sources or supplements [1]. The active form, 1,25-dihydroxyvitamin D [1,25(OH)₂D], interacts with the vitamin D receptor (VDR) expressed on immune cells such as macrophages, dendritic cells, and T lymphocytes. This interaction enhances innate immune defense by inducing antimicrobial peptides like cathelicidin and defensins, which disrupt the membranes of respiratory pathogens. Moreover, vitamin D modulates adaptive immunity by suppressing excessive pro-inflammatory cytokine release, thus reducing tissue damage during infection [2].
Multiple epidemiological and mechanistic studies have demonstrated an association between low serum 25-hydroxyvitamin D [25(OH)D] levels and increased susceptibility to respiratory tract infections [3]. For instance, Martineau et al. (2017) conducted a meta-analysis of 25 randomized controlled trials encompassing over 11,000 participants, which revealed that vitamin D supplementation reduced the risk of ARIs, especially among individuals with severe deficiency (<10 ng/mL) and those receiving daily or weekly dosing. Similarly, other cohort and observational studies have linked seasonal variations in vitamin D levels with peaks in influenza and common cold incidence during winter months, suggesting a possible causal relationship [4].
Nevertheless, despite these promising observations, inconsistencies persist in the literature. Several randomized controlled trials have yielded null or inconclusive findings, often attributed to differences in baseline vitamin D status, supplementation doses, dosing intervals, duration of follow-up, and participant demographics [5]. Furthermore, the optimal serum concentration required for immune protection remains debatable, with thresholds ranging from 20 to 40 ng/mL proposed by various authorities. The clinical relevance of vitamin D supplementation for respiratory health therefore warrants rigorous evaluation through well-designed controlled trials that account for these confounding variables [6].
The biological plausibility of vitamin D’s protective role against respiratory infections is supported by its ability to regulate both innate and adaptive immune responses. By enhancing macrophage phagocytic activity and promoting epithelial barrier integrity, vitamin D reduces viral replication and bacterial adherence [7]. Simultaneously, it attenuates the cytokine storm commonly implicated in severe respiratory infections by downregulating IL-6, TNF-α, and IFN-γ while promoting anti-inflammatory IL-10 production. Such dual regulation is of particular importance in conditions like influenza, COVID-19, and community-acquired pneumonia, where exaggerated inflammation contributes to morbidity and mortality.
Given these immunological mechanisms and the persistent global prevalence of vitamin D deficiency, investigating whether daily vitamin D supplementation confers measurable protection against ARIs remains a question of high clinical and public health significance
Therefore, it is of interest to evaluate the efficacy of daily vitamin D supplementation in reducing the incidence, duration, and severity of acute respiratory infections among adults with suboptimal baseline vitamin D levels through a double-blind randomized controlled trial.
MATERIALS AND METHODS
Study Design and Setting
This study was designed as a double-blind, randomized, placebo-controlled trial conducted at the Department of Internal Medicine, a tertiary care teaching hospital in India, between January 2023 and March 2024. The study protocol was approved by the Institutional Ethics Committee and registered with the Clinical Trials Registry of India. Written informed consent was obtained from all participants before enrolment. The trial was conducted in accordance with the Declaration of Helsinki (2013 revision) and Good Clinical Practice (GCP) guidelines.
Study Population
A total of 400 adult participants aged between 18 and 65 years were enrolled. Recruitment was conducted from hospital outpatient clinics, staff volunteers, and community health outreach programs. Eligible participants were required to have baseline serum 25-hydroxyvitamin D [25(OH)D] concentrations between 10 and 30 ng/mL, indicating insufficiency but not severe deficiency.
Inclusion Criteria
- Adults aged 18–65 years of either sex.
- Serum 25(OH)D concentration between 10–30 ng/mL at baseline.
- No acute respiratory infection in the preceding four weeks.
- Willingness to provide written informed consent and comply with study procedures.
Exclusion Criteria
- Known history of hypercalcemia, nephrolithiasis, or renal impairment (eGFR < 60 mL/min/1.73 m²).
- Chronic respiratory diseases (e.g., COPD, bronchial asthma requiring systemic steroids).
- Current or recent use (within 3 months) of vitamin D or calcium supplementation exceeding 800 IU/day.
- Pregnancy or lactation.
- Immunosuppressive therapy, autoimmune disease, or malignancy.
Randomization and Blinding
Participants meeting the inclusion criteria were randomized using a computer-generated block randomization sequence (block size = 10) into two equal groups:
- Group A (intervention group): Received vitamin D₃ 2,000 IU per day orally.
- Group B (placebo group): Received identical placebo capsules containing inert excipients.
Randomization codes were maintained by an independent statistician not involved in data collection or analysis. Both participants and investigators were blinded to group allocation throughout the study period. Capsules were dispensed monthly in identical opaque blister packs.
Intervention Protocol
The intervention group received vitamin D₃ (cholecalciferol) 2,000 IU daily for six months, while the placebo group received identical capsules devoid of active ingredients. Participants were advised to maintain their usual diet and avoid other vitamin D supplements or fortified products. Adherence was assessed at monthly follow-ups through capsule counts and compliance diaries.
Outcome Measures
The primary outcome was the number of acute respiratory infection (ARI) episodes per participant over six months. ARI was defined as the presence of at least two respiratory symptoms (e.g., cough, sore throat, nasal congestion, dyspnea, or fever ≥38°C) lasting 48 hours or more, confirmed by a physician.
Secondary outcomes included:
- Duration of illness (days) per ARI episode.
- Symptom severity scores (on a 10-point visual analogue scale).
- Changes in serum 25(OH)D concentrations between baseline and six months.
- Adverse effects, including hypercalcemia or gastrointestinal complaints.
Sample Size Calculation
The sample size was estimated using the formula for comparing two means, assuming a 25% reduction in ARI incidence with vitamin D supplementation, 80% power, 5% alpha error, and a 10% attrition rate. The minimum sample required per group was 180 participants, which was increased to 200 per group (total n = 400) to ensure adequate power.
Data Collection Procedure
Baseline demographic and clinical information, including age, sex, BMI, lifestyle factors (sunlight exposure, diet, smoking), and comorbidities, were recorded using a structured case record form. Participants maintained symptom diaries for ARI episodes, which were validated by study physicians during monthly visits. Serum 25(OH)D and serum calcium were measured using chemiluminescence immunoassay (CLIA) at baseline and after six months.
Statistical Analysis
Data were analyzed using SPSS version 26.0 (IBM Corp, USA). Descriptive statistics were expressed as mean ± standard deviation (SD) or frequencies (%). Between-group comparisons were performed using the independent samples t-test for continuous variables and the chi-square test for categorical variables. Repeated measures analysis of variance (ANOVA) was used to evaluate longitudinal changes in serum vitamin D levels. A p-value less than 0.05 was considered statistically significant.
Ethical Considerations and Safety Monitoring
All adverse events were recorded and reviewed by an independent Data and Safety Monitoring Board (DSMB). Participants developing hypercalcemia (>10.5 mg/dL) or reporting persistent side effects were withdrawn from the study and appropriately managed.
RESULTS
A total of 400 participants were enrolled in the study and randomized equally into two groups: vitamin D₃ supplementation (n = 200) and placebo (n = 200). Fourteen participants (7 from each group) were lost to follow-up, leaving 386 participants (193 per group) for final analysis. Baseline demographic and clinical characteristics were comparable between groups. The mean baseline serum 25-hydroxyvitamin D [25(OH)D] concentration was 21.6 ± 5.1 ng/mL across all participants. After six months of intervention, the mean serum 25(OH)D level significantly increased in the vitamin D group but remained nearly unchanged in the placebo group. The incidence and duration of acute respiratory infections (ARIs) were significantly lower among participants receiving vitamin D supplementation. No serious adverse events, including hypercalcemia, were observed in either group.
Table 1: Baseline Demographic Characteristics of Study Participants
This table presents demographic data, including age, sex, and BMI, demonstrating comparability between groups at baseline.
| Variable | Vitamin D Group (n = 193) | Placebo Group (n = 193) | p-value |
| Mean Age (years) | 39.8 ± 12.1 | 40.2 ± 11.7 | 0.74 |
| Male : Female ratio | 97 : 96 | 98 : 95 | 0.88 |
| Mean BMI (kg/m²) | 24.6 ± 3.2 | 24.8 ± 3.4 | 0.59 |
| Urban residence (%) | 63.7 | 61.1 | 0.61 |
Table 2: Baseline Serum Vitamin D and Calcium Levels
This table shows biochemical baseline levels before intervention initiation.
| Parameter | Vitamin D Group | Placebo Group | p-value |
| 25(OH)D (ng/mL) | 21.5 ± 5.0 | 21.7 ± 5.2 | 0.82 |
| Serum Calcium (mg/dL) | 9.3 ± 0.5 | 9.2 ± 0.4 | 0.37 |
Table 3: Change in Serum 25(OH)D Levels After Six Months
This table displays the significant rise in serum vitamin D levels following supplementation.
| Timepoint | Vitamin D Group | Placebo Group | p-value |
| Baseline | 21.5 ± 5.0 | 21.7 ± 5.2 | 0.82 |
| 6 Months | 38.9 ± 6.2 | 22.4 ± 5.3 | <0.001 |
Table 4: Incidence of Acute Respiratory Infections (ARIs)
This table summarizes ARI occurrence per participant.
| Outcome | Vitamin D Group | Placebo Group | p-value |
| Participants with ≥1 ARI episode (%) | 29.5 | 58.5 | <0.001 |
| Mean ARI episodes per participant | 0.68 ± 0.9 | 1.43 ± 1.2 | <0.001 |
Table 5: Duration of ARI Episodes (in Days)
This table compares mean illness duration between the two groups.
| Variable | Vitamin D Group | Placebo Group | p-value |
| Mean duration per episode (days) | 4.1 ± 1.8 | 6.3 ± 2.5 | <0.001 |
Table 6: Symptom Severity Scores (0–10 Visual Analogue Scale)
This table demonstrates reduced symptom intensity with supplementation.
| Symptom Severity | Vitamin D Group | Placebo Group | p-value |
| Mean severity score | 3.8 ± 1.2 | 5.9 ± 1.8 | <0.001 |
Table 7: Seasonal Distribution of ARI Episodes
This table outlines ARI occurrence across different seasons.
| Season | Vitamin D Group (%) | Placebo Group (%) | p-value |
| Winter | 44.0 | 61.1 | 0.008 |
| Summer | 27.4 | 18.6 | 0.06 |
| Monsoon | 28.6 | 20.3 | 0.09 |
Table 8: Compliance with Study Supplementation
This table reports participant adherence to prescribed supplementation.
| Compliance Rate | Vitamin D Group (%) | Placebo Group (%) | p-value |
| ≥90% adherence | 92.7 | 91.2 | 0.64 |
| 75–89% adherence | 6.2 | 7.3 | — |
| <75% adherence | 1.1 | 1.5 | — |
Table 9: Incidence of Adverse Events
This table shows that no major adverse reactions were reported.
| Adverse Event | Vitamin D Group (n, %) | Placebo Group (n, %) | p-value |
| Mild GI discomfort | 5 (2.6) | 6 (3.1) | 0.77 |
| Headache | 3 (1.5) | 4 (2.1) | 0.70 |
| Hypercalcemia | 0 | 0 | — |
Table 10: Serum Calcium Levels After Six Months
This table confirms biochemical safety regarding calcium metabolism.
| Parameter | Vitamin D Group | Placebo Group | p-value |
| Serum Calcium (mg/dL) | 9.4 ± 0.6 | 9.2 ± 0.5 | 0.09 |
Table 11: Subgroup Analysis by Baseline Vitamin D Status
This table compares ARI incidence according to initial 25(OH)D strata.
| Baseline 25(OH)D (ng/mL) | Vitamin D Group ARI Episodes (mean ± SD) | Placebo Group ARI Episodes (mean ± SD) | p-value |
| 10–20 | 0.74 ± 1.0 | 1.58 ± 1.2 | <0.001 |
| 21–30 | 0.61 ± 0.8 | 1.27 ± 1.1 | <0.001 |
Table 12: Summary of Primary and Secondary Outcomes
This table provides an overall summary of intervention outcomes.
| Outcome | Vitamin D Group | Placebo Group | p-value | Effect Size |
| Mean ARI episodes | 0.68 ± 0.9 | 1.43 ± 1.2 | <0.001 | 0.42 |
| Mean duration (days) | 4.1 ± 1.8 | 6.3 ± 2.5 | <0.001 | 0.56 |
| Mean symptom score | 3.8 ± 1.2 | 5.9 ± 1.8 | <0.001 | 0.48 |
Table 1 established that both groups were demographically similar, ruling out confounding baseline variability. Table 2 confirmed equivalence in baseline biochemical parameters, ensuring internal validity. Table 3 revealed a statistically significant increase in serum 25(OH)D in the intervention group, confirming effective absorption and adherence. Table 4 demonstrated that vitamin D supplementation significantly reduced ARI incidence, while Table 5 and Table 6 highlighted reductions in both illness duration and symptom severity, indicating improved clinical recovery. Table 7 suggested that protective effects were particularly notable during winter months when baseline vitamin D levels were lowest. Table 8 reflected high compliance rates across both groups, strengthening data reliability. Table 9 and Table 10 confirmed the safety of daily supplementation without biochemical abnormalities. Table 11 revealed that participants with lower baseline vitamin D benefited most, supporting dose-responsiveness. Finally, Table 12 consolidated these findings, showing strong statistical significance across all primary and secondary endpoints, thereby reinforcing the preventive efficacy and safety of daily vitamin D₃ supplementation in reducing acute respiratory infection burden.
DISCUSSION
This double-blind randomized controlled trial was conducted to evaluate the efficacy of daily vitamin D₃ supplementation in preventing acute respiratory infections (ARIs) among adults with suboptimal baseline serum 25-hydroxyvitamin D levels [8]. The findings of this study demonstrate a statistically and clinically significant reduction in both the incidence and duration of ARIs in participants who received daily vitamin D supplementation compared to those who received placebo. Moreover, the supplementation regimen was safe and well-tolerated, with no reported cases of hypercalcemia or major adverse effects [9].
The results corroborate and extend the growing body of evidence that implicates vitamin D as a key immunomodulatory factor influencing susceptibility to respiratory infections. The significant rise in mean serum 25(OH)D concentration from approximately 21.5 ng/mL to 38.9 ng/mL among supplemented participants indicates that the dosage of 2,000 IU/day was adequate to restore and maintain sufficient vitamin D status [10]. This biochemical improvement was associated with a 52% reduction in the incidence of ARI episodes and a 35% reduction in mean illness duration, consistent with mechanistic evidence that vitamin D enhances host defense by upregulating antimicrobial peptides and modulating inflammatory cytokine profiles [11].
Several previous trials and meta-analyses have reported similar trends. Martineau et al. (2017) in a pooled analysis of 25 randomized controlled trials involving over 11,000 participants found that vitamin D supplementation reduced the risk of ARI by 12%, with the greatest benefits observed in those with baseline deficiency and in trials employing daily or weekly dosing rather than large intermittent boluses [4]. The current study supports this conclusion by using a daily regimen, which likely provided a more stable serum concentration conducive to immune regulation. Furthermore, the magnitude of protection observed here (about 50% risk reduction) is higher than average meta-analytic estimates, possibly due to the relatively homogeneous baseline deficiency status of the participants and consistent compliance achieved under supervised clinical monitoring [12,13]. The immunological rationale underlying these findings has been well established. Vitamin D receptor (VDR) activation in immune cells stimulates transcription of antimicrobial peptides such as cathelicidin and β-defensin-2, enhancing mucosal defense against respiratory pathogens. Concurrently, vitamin D attenuates the exaggerated pro-inflammatory response often seen in severe viral infections by downregulating interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) while promoting anti-inflammatory interleukin-10 (IL-10) [14]. This dual role helps maintain epithelial integrity, reduce viral replication, and limit collateral tissue injury mechanisms that together contribute to reduced infection frequency and symptom severity as observed in this trial [15].
In addition, the seasonal distribution analysis demonstrated that the preventive effect of vitamin D supplementation was most pronounced during winter, a period typically associated with lower ultraviolet B exposure and consequently reduced endogenous vitamin D synthesis. This observation reinforces the concept of seasonal susceptibility mediated by vitamin D fluctuations and supports the potential for targeted supplementation during months of reduced sunlight exposure [16]. From a safety perspective, the supplementation dose of 2,000 IU/day proved to be well within the tolerable upper intake level and did not induce hypercalcemia or adverse metabolic effects. Previous safety evaluations have confirmed that daily doses up to 4,000 IU are generally safe for healthy adults, and the current findings further substantiate that moderate-dose continuous supplementation provides effective immune benefits without toxicity risks [17]. The findings also hold significant implications for public health policy. Vitamin D deficiency remains highly prevalent in India and other low-latitude countries despite abundant sunlight, largely due to indoor lifestyles, clothing habits, skin pigmentation, and dietary insufficiency. The observed preventive benefit against ARIs suggests that correcting this deficiency through safe, low-cost supplementation could represent a practical strategy to reduce the overall burden of respiratory illness, lower antibiotic use, and minimize productivity loss due to frequent infections. In addition, during global pandemics such as COVID-19, adequate vitamin D status may serve as an adjunctive protective measure, given its established immunomodulatory effects and the observed associations between low vitamin D levels and adverse respiratory outcomes [18]. Despite these encouraging findings, several limitations must be acknowledged. First, the study population was limited to adults aged 18–65 years without chronic comorbidities, and the results may not be generalizable to pediatric, geriatric, or immunocompromised populations. Second, ARI diagnosis was based on clinical criteria rather than microbiological confirmation, though this approach reflects real-world community practice [19]. Third, while serum 25(OH)D was measured at baseline and at the end of the study, intermediate assessments might have provided greater insight into the temporal relationship between vitamin D levels and infection dynamics. Lastly, the six-month follow-up period may not capture long-term sustainability of the preventive effect [20].
Nevertheless, the study’s strengths include its robust randomized double-blind design, large sample size, strict adherence monitoring, standardized outcome definitions, and comprehensive statistical analysis. The use of a daily dosing schedule with a physiologically relevant dose enhances external validity and clinical applicability. Importantly, the trial demonstrated a consistent pattern of benefit across subgroups stratified by baseline vitamin D levels, indicating that individuals with both moderate and mild deficiency may derive measurable advantage from supplementation.
In summary, the present study provides strong evidence that daily oral vitamin D₃ supplementation at 2,000 IU effectively prevents acute respiratory infections, shortens illness duration, and reduces symptom severity in adults with low baseline vitamin D status. The findings emphasize the potential of vitamin D optimization as a simple, safe, and scalable preventive intervention against respiratory infections.
Future research should focus on evaluating long-term benefits, cost-effectiveness analyses, and implementation strategies for population-level supplementation programs. Moreover, trials including high-risk groups such as elderly individuals, healthcare workers, and patients with chronic lung disease could further refine dosage recommendations and optimize preventive strategies for different demographic categories.
CONCLUSION
This double-blind randomized controlled trial demonstrates that daily supplementation with 2,000 IU of vitamin D₃ significantly reduces the incidence, duration, and severity of acute respiratory infections among adults with suboptimal baseline serum 25(OH)D levels. The intervention effectively raised serum vitamin D concentrations without causing adverse effects, underscoring both its efficacy and safety. These results highlight the immunoprotective potential of maintaining adequate vitamin D status and suggest that routine screening and supplementation could serve as a cost-effective preventive measure to mitigate the burden of respiratory infections in the general adult population. Broader implementation of vitamin D supplementation programs, especially during winter months and in populations with high deficiency prevalence, may substantially improve community respiratory health outcomes.
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Comments
Heh...this is a shady study if I ever saw one.
-- Exactly 400 study participants recruited.
-- Exactly 193 of 200 participants completing the study in each group (which, for a study administered in a community setting, is an essentially impossibly-high completion rate).
-- No author disclosures -- in fact, no information about the authors whatsoever, other than their names.
-- No information on exposures, lifestyles, or other factors which invariably influence infection rates.
-- Inappropriate statistical methods, which focus very heavily on p values.
-- Only 3 authors, which for a randomized controlled trial involving hundreds of people in different settings with regular follow-up, seems rather unlikely.
By roflmaostc 2025-10-2817:551 reply In the PDF they are all titled as
"Assistant Professor, Department of General Medicine, Arundathi Institute of Medical Sciences, Dundigal, Medchal Malkajgiri, Telangana, India"
The 2nd author is listed here: https://aims.ac.in/general-medicine/ I did not find any trace for the other two authors (do they exist?).
Also, look at the timings: Received: 16-09-2025 Accepted: 29-09-2025 Available online: 14-10-2025
That's relatively fast but also the paper is not super in-depth.
And in general it seems like that the "International Journal of Medical and Pharmaceutical Research" is not quite well known. See the Editors, not even pictures there: https://ijmpr.in/editorial-board/
By roflmaostc 2025-10-2817:59 The first author is probably him: Dr. G Naresh (Asst. Prof.)
By roncesvalles 2025-10-2818:081 reply My bullshit meter redlined as well.
> Incidence of ARIs was documented through monthly follow-up visits and self-reported symptom diaries validated by physician assessment.
This is basically impossible to accomplish for 386 participants who aren't in some form of captivity (e.g. incarcerated, institutionalized, in the military, or a boarding school). Nobody cares enough to maintain a "self-reported symptoms diary" and make monthly visits for some study. If they actually ran the study as designed, they would've have zero usable participants even starting from 400.
Saying nothing of the ethics of giving half the Vitamin D deficient patients presenting at your clinic with a placebo.
By givemeethekeys 2025-10-2819:111 reply > (e.g. incarcerated, institutionalized, in the military, or a boarding school).
That's a pretty big list. Add Retirement communities and your pool increases even more. Add to that the fact that this is India where the population is at least 5x bigger and much more concentrated..
Most retirement communities don't have that much supervision.
Regardless, you can get a lot of data, but of it is from people who have other significant differences in lifestyle from the average person and so it is questionable how it applies. Military gets more physical fitness (we already know most of us need more). Boarding school implies young - children or just older, and so while not useful there are differences related to that to control for (military as well, unless you can get officers who are older thus allowing controlling for age).
By JumpCrisscross 2025-10-2820:141 reply > Most retirement communities don't have that much supervision
Retirement communities in India are relatively new. Most older folks get taken care of at home by domestic staff, which, given India's demographics, are incredibly cheap and thus plentiful.
I forgot this was India, my mistake. Though that means there are essentially no retirement communities to work with there.
By givemeethekeys 2025-10-2822:03 There are retirement communities in India and end-of-life care centers as well. Societies change, and thanks to the internet, societies change faster than ever.
By NedF 2025-10-290:26 [dead]
By zahlman 2025-10-2819:21 > It is: Negative, Unproductive, Antagonist, non Factual and frankly futile (unless provocative).
The comment gives clear reasoning and makes claims about the contents of the paper that are supported by reading the paper. To call it "non-factual" is simply incorrect. The word "futile" is nonsensical in this context.
You used three different words to complain that the comment critiques the study. There is nothing wrong with such critique in comments here, and indeed a healthy community requires that critique can rise to the top where it's warranted.
> Have you done an experiment lately to show counter proof? Beside claims what else do you have!
This is completely logically irrelevant, and suggests a fundamental misunderstanding of logic. Pointing out that a study is flawed does not require providing evidence for the opposite of the study's conclusion.
> This paper is very positive
A paper being "positive" has nothing whatsoever to do with whether its finding is correct, and it also has nothing whatsoever to do with whether its methodology is valid, and it also has nothing whatsoever to do with whether it accurately reports what was actually observed (i.e. whether any kind of fraud was involved).
> It is in fact (by personal experience)...
It is fundamentally impossible to know those things "by personal experience". That's why studies exist.
By mapontosevenths 2025-10-2819:221 reply > It is in fact (by personal experience) essential for the health
You might be right, but this study doesn't show that because it's a genuinely bad study. Someone serious should do a real study on it.
This was meant for Gwerbret (but he deleted the comment). Now is to whom may concern :) Standing by your words you think this paper is shady and you are questioning the work and results behind it. Moreover your comment somehow is on the very top it misleading the users or at least ridiculing the paper. Answering to you: It is indeed very much connected to the LEVELS of Vit D not the absence of it. You fail to understand and acknowledge the importance of the results (even though you already know and confirm the benefits of Vit D). Regulating the levels of it (keeping them higher then average) it prevents health issues by regulating many biological functions/pathways, raising the immunity and lifespan in general. This is the real cure which prevent incredibly terrible future health issues and suffering.
Edit: Just for this effort, this paper deserves Credit. Bravo.
By pinkmuffinere 2025-10-2820:08 > Just for this effort, this paper deserves Credit. Bravo.
I just went out and did a study myself. But I got 10,000 people, and 100% of the participants gave usable data, with a full record of every action taken, and every possible result. My study shows with 99.99% confidence that vit D is actually _bad_ for you. I hope you will congratulate my positive result (saving people from the dangerous effects of vit D !!) Or at the very least, congratulate me for my effort.
Obviously I completely fabricated that. Do you see how _claiming_ something doesn't mean it's true? Can you see the many red flags in my paragraph above? The other posters are pointing out similar red flags in the main article that's been shared.
By markhahn 2025-10-2818:58 I think the strongest criticism is just that being short of just about anything would cause significant effects. being short of water, calories, any vitamin, protein, etc.
Wanting to agree with a study’s conclusions and so ignoring its weaknesses and red flags is bad scientific practice, further reinforcing the comment questioning the value of this publication
By trilogic 2025-10-2819:54 Maybe you are right, on ignoring a study weaknesses and red flags is bad scientific practice. Is that I have been involved personally so long in this topic, that I know for a fact that the results are Good. As I also know many good studies being ridiculed and buried on purpose. No one in the scientific community would dare to criticize a paper in that way. Constructive criticism is connected to intellectual, educated minds, all the rest deserves the same coin or being ignored. I still don´t understand why that comment on top, (I have seen this to many times).
By unionjack22 2025-10-2816:014 reply Vitamin D, red light therapy, insulin attenuating response of a walk, immunological benefit of allergen exposure, cognitive noise reduction and rest response of walks in forests.
Man keeps trying to bring the outdoors inside.
While I find your comment enjoyably pithy, in the case of vitamin D, many humans are currently living at latitudes which they are not suited to (skin being too dark to generate enough vitamin D given the insolation), and eating diets which do not provide them with sufficient amounts of it (the carnivore diets of Inuits and similar groups being a good contrast).
Amusing how thanks to the war on cholesterol the UK unravelled a lot of egg eating habits - a natural source of vitamin D.
The UK also consumed a lot more liver than it does today I imagine...
Vitamin D supplementation in the UK - now there is a fascinating topic.
With the industrial revolution there was a problem of kids in cities getting rickets. This was due to a lack of vitamin C and that was due to a lack of daylight due to the smog.
The solution was to take the kids out of the city so they could spend time in the countryside.
However, along with the industrial revolution came steam trains, and, with steam trains, it became a lot easier to get fresh food from the farm to the city table.
Milk became an early commodity for this railway trade, in the days before refrigeration. Bottling had to be invented too, along with pasteurisation to get the modern milk product. They fortified it with vitamin D and, in time, made it mandatory in schools for kids to have dinky bottles of milk for their morning break. All kids hated the stuff but it was 'good for them' and good for keeping farmers gainfully employed.
Then the clean air acts came along, with the first street to ban fires in fireplaces being opposite the smoke free coal factory, the factory being anything but smoke free. Deindustrialisation happened too, so there were no cities with smokestack industries at their heart.
With clean air there was no longer any need to fortify the milk with vitamin D, so that stopped. From now on, kids would get their vitamin D doing things such as playing in the school playground.
But then we became seriously car dependent and the age of the free-range child was over. With 'stranger danger' and screens (initially just TV) taking over, we entered a new era of people not getting enough daylight again.
Along the way vitamin D has been downgraded, much like Pluto, from being a 'vitamin' to being a hormone. A lot of people want to point this out and explain the science to you. From hearing how some talk about vitamin D, it sounds like the recommended supplements are all over the place.
Clearly there are millions, if not billions that seem to be living just fine with not much sunlight in their lives and on no vitamin D supplements. Where's the rickets? Good question, but then, in Antarctica, where there are months of darkness to endure, they are on something like 20,000 units a day, and they probably know what they are doing.
Maybe following their example for this winter could be my next 'nutrition experiment'. Sometimes, when there is so much conflicting information, it is best to do an n=1 experiment with one's own body.
By thewebguyd 2025-10-2821:021 reply > Maybe following their example for this winter could be my next 'nutrition experiment'
Anecdotal and a sample size of 1, but I tried supplementing Vitamin D last year in the winter months. I live in the PNW, which between October and March, the sun is too low to trigger vitamin D synthesis in the skin to see if it had any effect on my energy levels and mood, I suffer from seasonal affective disorder pretty severely.
Taking 5,000 IU daily had no noticeable effect for me. A slight increase in energy levels but not significant enough that I'd be confident in attributing it to supplementation. I was hesitant to supplement more without medical advice and a blood test.
That's not to say Vitamin D isn't important (it is), and the scientists in Antartica definitely know what they're doing, but it's more to say YMMV.
For me, just making an effort to do more physical activity outdoors during the dark months had more of an impact
~5000 IU daily between February and May was barely enough to raise 25(OH) D level in my blood from 9 to 30 ng/ml.
Depending on who you ask, 30 is either the bound between "deficient" and "insufficient", or between "insufficient" and "sufficient". Regardless of who you ask, there's plenty of headroom until "excess".
By rcxdude 2025-10-299:21 Yes, it's possible but relatively hard to overdose on vitamin D, and due to a cock-up in some calculations in a study, until recently the recommended supplement amounts were about an order of magnitude too low: https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
By rcxdude 2025-10-299:17 The NHS does recommend that everyone in the UK 'consider' vitamin D supplementation during the autumn and winter: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-... , because the amount of sunlight available in those months is not enough to maintain a healthy level.
By markhahn 2025-10-2915:29 I don't think vit c has anything to do with daylight/smog. vit d, definitely (and so not rickets).
By LtdJorge 2025-10-2821:03 > This was due to a lack of vitamin C and that was due to a lack of daylight
I think you also meant Vitamin D there
By lawlessone 2025-10-2818:281 reply Are they that unpopular? Seem like a staple of an English Breakfast.
By djtango 2025-10-292:38 Couldn't quickly find any sources for the UK specifically but this should suffice
It’s criminal that the US sent Somalian refuges to live in Minnesota. Those are some seriously brown people in the land of no vitamin D. Pretty big population in Seattle as well, which is worse due to cloud cover.
By thewebguyd 2025-10-2821:061 reply > which is worse due to cloud cover.
Not just cloud cover. Most areas in the PNW, the sun is so low in the sky between October and March that you can't synthesize vitamin D through the skin at all during those months, even on a bright sunny day.
Even during the summer up here, you really only get a window of roughly 10am to 3pm where enough UV-B rays can penetrate the atmosphere, in July. It's estimated that >80% of the PNW population are deficient (compared with 40% nationwide in the US).
By hinkley 2025-10-2823:27 That same podcast I mentioned pointed out that if a white person nude sunbathed in the winter in full sun, you’d get 2nd degree burns long before you made enough vitamin d.
The body stores it though. So how much of a deficit you’re running for how long matters.
By hinkley 2025-10-2818:01 I knew it was Minnesota, not sure why I wrote WI.
It's only criminal if they aren't provided with the education/information they need to live healthy lives (which is possible with the right diet/supplements).
Dark skinned people do not produce enough vitamin D in northern latitudes because of melanin. If you’re black and in Minnesota you probably need supplementation.
By vintermann 2025-10-298:101 reply Minnesota? Minnesota isn't particularly dark. Minneapolis is apparently on the same latitude as Venice, Italy, and I don't think of Venice as particularly dark or gloomy (to be fair, they probably have better weather).
But yeah. Low vitamin D levels are common even with lily white people in Northern Europe, and at least here in Norway everyone with dark skin knows that they need vitamin D supplements. Traditionally, public health recommendation (for everyone) was to take cod liver oil regularly for every month with an R in it.
By hinkley 2025-10-2914:52 To your eyes. But the sun angle chews up the wavelengths that make vitamin D.
By mwambua 2025-10-2820:18 I’m painfully aware of that being dark skinned myself. That doesn’t mean that Minnesota is inhospitable though (or that it would be criminal to send me there). It just means that they’d need to know that they need vitamin D supplements and perhaps regular blood screens. Idk if that happens though.
They have all already disappeared form public and it's only in the 40s right now. By winter you would swear no Somalis live in MN.
By hinkley 2025-10-2823:31 There are towns in Canada that have heated hallways that go between buildings so you can’t get completely snowed in during the winter. Maybe they should build those. Or the underground walkways they have in a couple of the cities.
It was never about doing right for people, it was about making unbelievable gobs of money using them as pawns.
By hinkley 2025-10-2821:22 I mean I guess they could have dumped them in West Virginia or Kentucky and that would have been much much worse.
I'm an Asian who was born and raised in a tropical weather region of my country. I'm now living in the PNW region of the US and it's always miserable from November-April. Vitamin D helps but it's not the same.
By hinkley 2025-10-2823:30 Seattle taught me a lot about procrastination. If you look outside and it’s sunny, and you promised yourself you’d go out today, drop whatever you’re doing and put on a jacket. Because by the time you finish it might be cloudy again. Seize the hour. There are no days to seize.
By loverofhumanz 2025-10-2816:382 reply Man suffered outdoors very much, for a million years.
Man want both good of indoors and good of out outdoors.
By SketchySeaBeast 2025-10-2817:293 reply Indoors best invention since fire.
By SAI_Peregrinus 2025-10-2818:001 reply Doors are such an important invention that multiple unrelated animals have evolved modified body parts to serve as doors to burrows¹. Being able to store food is critically important for surviving low-food periods like winter without migrating. "Indoors" lets you store food without insects or other animals getting to it & stealing it. Fire allows for hardening clay, which lets you make a special tiny "indoors" called a "pot" for storing food. Also bricks so "indoors" can be made anywhere. With a roof the rain stays out & you can stay dry & warm, and not freeze at night. A significant portion of why fire is so important is it enables creating various sorts of "indoors".
By thaumasiotes 2025-10-2818:132 reply > "Indoors" lets you store food without insects or other animals getting to it & stealing it.
This isn't true of human doors; insects are very small.
We've had the technology to keep things in wax-sealed clay jars for quite a while, but I'm not aware that this was done with grain, where preventing spoilage would have been most valuable. Granaries are open to the air. (And devote quite a lot of effort to slowing the spoilage of the grain.)
If you wanted food that wouldn't rot, instead of keeping it in an airtight environment, you dried it.
Maybe better.
If I have to survive the night, overhead protection and thermal insulation is more important than a fire. Source: I've tried using both without the other.
By SketchySeaBeast 2025-10-2820:43 There's definitely a reason we use tents while camping and don't just huddle around the fire.
By SketchySeaBeast 2025-10-2818:431 reply Man love synergy.
By hinkley 2025-10-2914:51 You not from tribe.
By formerly_proven 2025-10-2819:491 reply Fire indoors but smoke outdoors.
By hinkley 2025-10-2820:08 <grunt>
By supportengineer 2025-10-2817:531 reply Few words good
By IAmBroom 2025-10-2818:18 fewer gooder
By al_borland 2025-10-2817:431 reply While I’d love to just go for a walk outside, the allergen exposure of the outdoors is too high most of the time. This elements any mental health benefits a walk in a forest might otherwise give.
By al_borland 2025-10-2820:36 I’m currently getting allergy shots. This is my 3rd attempt. Throughout my life I’ve gotten shots for about 12 years now. The last guy said they were better than I was kid and basically a cure now. 6 years later, and on the strongest dosage they’d give, getting 3 shots with each appointment… and I was never able to spend time outside without worry of what would follow.
There has been minor improvement in controlled testing, but no noticeable benefit when actually trying to live life. I go outside near nature once each year as a test to see if there was any progress. I can’t tolerate much more than that.
Shots work well for some. They worked decently well when I was a kid, but these days, not so much. I still hope the current ones will work, as I don’t have other options, but I’m beginning to lose hope.
Privileged comment. Walks in a controlled greenhouse without allergenic pollinators also work, but the poor can't easily access either in the US.
By pavel_lishin 2025-10-2818:40 > Privileged comment.
Shall we stop discussing any possible solution which might be out of reach for someone?
By switchbak 2025-10-2819:47 Privileged commenter. Not everyone has access to a cell phone or the internet, so they can't respond to your statement. Not to mention some people have bad dyslexia or eyesight issues. We could play this game forever, and we'd all be dumber for it.
Walking in a forest is something that much of humanity can do, and it's not a particular privilege (in the pejorative modern sense) - even if there are a small number of people that have issues that would prevent this.
By philipallstar 2025-10-297:15 Anti-allergy pills are some of the cheapest[0] and safest products on the market.
[0] https://www.walgreens.com/store/c/walgreens-allergy-relief-d... $4.99 for 24x 1-a-days
How do I bring outdoors to the wage slave office? And how do I bring light to the pre-work and afterwork when there is no sun at those times?
The practical man uses technology to offset the prison built for him. The hapless enabler farms “pithy” HN points in his LED-lit room.
Most vitamins are a waste of time and money, some are even harmful[1], but there are a lot of people with D deficiency, especially in winter[2].
1 https://www.mdpi.com/2072-6643/17/17/2744#:~:text=highest%20...
2 https://www.abs.gov.au/articles/vitamin-d#edit-group-image--...
The issue I've found with these discussions is it appears there's mixed evidence on if vitamin D *supplementation* actually has a positive impact, regardless of vitamin D deficiency. In other words, is the deficiency causal or correlative.
I have no opinion on the matter, and am inclined to think there is at least some positive benefit. But YMMV
By theshrike79 2025-10-2816:005 reply The problem is that vitamin D doesn’t absorb the same way for everyone.
If a 100 people take 50IU of Vitamin D, you get 100 different results.
Some get enough from minor sun exposure and maybe eating a fish now and then. Others need massive doses to get any results.
By johnisgood 2025-10-2817:091 reply 50 IU is nothing. 3000 IU is something. I have MS, so I need to supplement at least 10k IU.
And yeah, it does not absorb well unless you eat some fat.
I took 10k iu via a multivitamin for a few months, and ended up with Vitamin D levels 5x higher than the maximum on the labcorp reference range. "Vitamin D toxicity"
It took many months to get the levels back to normal. Vitamin D is one of those things that once you overdose, it takes many months for the levels to slowly come down after you stop supplementing.
Be careful with Vitamin D!
The downside to having high levels is plaque/calcium deposits in arteries, if I'm not mistaken. Which can be mitigated by taking K2.
By 0xbadcafebee 2025-10-2819:342 reply Are you aware of the history of setting acceptable levels of Vitamin D? Basically, 100 years ago, people experimented with cures for TB by giving patients one to two orders of magnitude higher dosage than the "vitamin D toxicity" levels reported today. Like insanely high numbers. Strangely enough, most people did recover from the TB, but they kept getting the treatments anyway, and that in a few instances led to bone issues. So for some reason that doesn't seem to be documented, they set the "safe level" of vitamin D to be something like two orders of magnitude lower than the level that actually caused issues. And that level has never been changed.
All of the studies I've seen around Vitamin D supplementation has shown that the "safe level" reported today is way, way lower than it should be. People appear to be just fine taking 10k IUs for months on end, even 7 years in one study. I think what we're learning is that the "safe level" is a very wide spectrum; some people could possibly be harmed from a low level, whereas some people are perfectly fine at a very high level.
By johnisgood 2025-10-2819:50 Yes, and many people are fine with 10k IU for months because their body just does not absorb it well.
And some people, like those with MS (such as I) need to take more than usual. Someone I know has MS and takes 20k IU and gets regularly tested.
By nomel 2025-10-2823:00 And, fixed dosage never makes sense with Vitamin D. If you're supplementing, you need to make sure you regulate it based on sun exposure, since it's literally the Sun vitamin.
It's easy to double up if you decide to eat lunch outside because the weather is nice this month. I take 10k only if I'm indoors all day, and reduce or take none if I'm out.
> An excess of vitamin D causes abnormally high blood concentrations of calcium, which can cause overcalcification of soft tissues, including arteries and kidneys. Symptoms appear several months after excessive doses of vitamin D are administered. A mutation of the CYP24A1 gene can lead to a reduction in the degradation of vitamin D and thus to vitamin toxicity without high oral intake (see Vitamin D § Excess).
> Treatment
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month. Bisphosphonate drugs (which inhibit bone resorption) can also be administered.[2]
Regardless, blood levels need to be checked for this sort of thing and doses are not one-size-fits-all. I also once was taking 10k daily, for several months, and ended up just barely in excess territory with no noticeable symptoms. (I settled on taking 4k daily in the long term.)
By cj 2025-10-2821:40 > In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month.
Surprised to see just 4 weeks for a recovery. I got retested after 8 weeks (only minor improvement) and wasn't until 16 weeks until the test finally came back in range.
100% no dose is one-size-fits-all. I overdosed from taking a specialty multivitamin (it has a discord channel and everything). So was chatting with people taking the same vitamin, same dosages, also getting tested, but others had no issues at the same doses.
I guess I just absorb vitamin D with great efficiency, who knows.
By johnisgood 2025-10-2819:32 > An excess of vitamin D causes abnormally high blood concentrations of calcium
That is what supplementing K2 with D3 is for, too.
By johnisgood 2025-10-2818:51 Yeah, you should take vitamin D with K2 at the very least.
Thanks for the tip though. I do not take it regularly so I think I'm fine. :D
By LocalPCGuy 2025-10-2816:45 Echo this with a PSA: it's a simple test to get your levels, and I'm a proponent of ensuring it's included when you have other regular blood tests (may have to ask for it). That can allow a person to see patterns, how effective any supplementation (and different amounts) are, etc.
By detinho 2025-10-2818:38 I can use myself as an example: I have crohn's disease and I can take doses of 50000UI for some weeks, then 4000UI daily and after a year have my Vitamin D results as low as 20ng/ml.
50IU is a minuscule dose though, no? If people are recommended to supplement, they generally take a dose in the range of a few thousand.
By theshrike79 2025-10-290:091 reply The point wasn't the dose, I just picked a number out of my ass.
The point is that from that N IU the 100 people will absorb anything from 0-N, it's very individual and varied.
The only way to be sure is to test your levels, which costs money every time. There really should be a simple and cheap home test kit for it. You'd sell millions every year just in the Nordics and Canada =)
Maybe this comes across snide, but have you been to the Nordics? I can get tested at my GP for free practically as often as I'd like, I doubt you'd sell too much in the way of home test kits.
By theshrike79 2025-10-2912:38 Been living here my whole life.
I've been offered a (free) Vitamin D checkup exactly zero times. We should be getting them though, dunno why we don't.
There is no way that's what they meant. 50k is an absurdly large dose that's way outside the safe intake range. 10k is used sometimes under medical supervision and even then it's a very short term measure. For long term intake, 4000IU is a widely accepted safe upper limit. 50k is an order of magnitude more than that.
By 0xbadcafebee 2025-10-290:17 There's plenty of documentation of people taking 50k for a period of time and having no side effects. There's been something like a dozen trials using high doses like this to treat TB, and they're usually successful, with no significant negative symptoms.
Conversely, some studies have shown that 4k IU does contribute to hypercalcemia in a small number of cases (4 per 1000). So actually 4k is deemed "not completely safe" as a limit.
The point is, the amount you take needs to be adjusted by a clinician, as the safe range for you is unknowable otherwise.
If your doctor is not seeing results they’ll keep upping the dose and I’ve heard of some that sound like an attempt at assisted suicide. Most of us would get toxicity from some of the ones I’ve heard.
By jaggederest 2025-10-2818:081 reply My family is in this group. We are poor absorbers of vitamin D, some of my elder relatives need 5 times the "safe upper limit" to have healthy blood levels. As long as you're checking your blood values routinely (and for both D2 and D3, not just one or the other), it's reasonably safe. Sort of like other prescriptions in general.
By hinkley 2025-10-2818:20 I heard about a guy who ordered a bottle and ended up with vitamin D poisoning, on one of those Ira Glass style podcasts. Turns out they forgot to compound it before sending it out so he was getting “cask strength” vitamin D. Sounded very unpleasant.
By nradov 2025-10-2816:41 Most of the vitamin D supplement studies have been very low quality in that they give all subjects in each group a fixed amount (or placebo). Ideally they should periodically test blood levels and titrate the dose to hit a target range. This would get us closer to establishing causality (or lack thereof) including a response curve. The amount needed to hit a given target will be wildly different for many individuals based on factors that are still not well understood.
By LocalPCGuy 2025-10-2816:41 Just my results (n=1) and I don't think this is exactly what you were saying, but just in case other read it the same way I did at first: having had (lab tested) vitamin D deficiencies, vitamin D supplementation can help to restore levels back into the desired range. So supplementation can have the desired effect of improving vitamin D levels (more below). It is a simple test that most doctors don't quibble about adding on to other blood tests (i.e. during annual checkup, for instance), but isn't generally checked by default. (note: insurers may want it to be "diagnostic" rather than "preventative" in order to cover the test.)
Whether it has a "positive impact" on overall health (which I believe to be your point), that would be even more anecdotal and also impossible for me to narrow down whether that one factor had any significant effect, so I won't posit that. And I agree that from different studies I've read, the actual science on it is pretty varied and I haven't seen anything conclusive. Even this study notes their conclusion was "... among adults with suboptimal baseline vitamin D levels".
This is solely my own anecdote, but I used to get bad seasonal depression every winter. I tried a number of interventions short of medication; none moved the needle very much. I started supplementing with vitamin D probably 8 years ago and haven't had any issues with seasonal depression since.
I'm pretty personally convinced that it was the supplements that helped here.
I tried a 1000 IU vitamin D pills to no avail. Bumped it up to 5000 IU and still saw very marginal bumps in my blood tests
I think I might try daily 10000IU after showing my doctor how little it's moving the needle for me
I was put on prescription vitamin D2 50000 IU and it caused a bunch of side effects for me including heart palpitations for over a week and then a paradoxical reaction to magnesium causing them to be even more intense.
Proceed with caution and listen to your body. Doctors were accusing every other thing than accepting whatever it did to my calcium / other electrolytes bothered my heart.
By benregenspan 2025-10-2817:201 reply It's expensive in the US because one company has exclusive sales here (patent protection?), but you could try calcefidiol, weekly dose and is supposed to get levels up rapidly. Apparently it's the common form to take in Spain, and it's further down the metabolic pathway vs cholecalciferol. (I take but still have to get levels checked)
By MisterPea 2025-10-2818:22 thank you, will have to check this out
By swalsh 2025-10-2818:47 I can tell you supplementation works 100%.
I took a blood test several weeks ago, my Vitamin D level was 14 ng/ml. I was so fatigued there were times I had to lay on my office floor because I didn't even have the energy to sit in my chair. I started taking 50k IU's weekly and then 10k IU's daily, and the results were dramatic. I went from having 0 energy to nearly normal. I also had soreness in my legs which went away.
Vitamin D isn’t technically a vitamin in the strict sense, because unlike the other vitamins the human body can produce it itself (by exposure to sunlight).
By rhdunn 2025-10-2818:52 The body can also synthesize vitamin A from beta-carotene which is effectively two vitamin A molecules joined together (one rotated 180deg relative to the other).
By slow_typist 2025-10-2816:323 reply Dogs can synthesise vitamin C…
By lxgr 2025-10-2818:13 Sure, many things are vitamins for one species but not another. (In fact, every vitamin must be able to be produced by at least one species – where else would it come from?)
Wow, that is interesting. They can synthesise it in their liver?
Many animals can. There are a gene for it, humans don't have it. There is a lot of speculation as to why, but nothing really stands out (possibly just random chance - if you eat enough there is no advantage to keeping the gene and in turn no loss from losing it. However I'm unable to rule out other possibilities) https://pmc.ncbi.nlm.nih.gov/articles/PMC3145266/ is a really interesting survey of the issue across many different species.
By schuyler2d 2025-10-2819:061 reply From the article: > Another argument supporting the suggestion that species which have lost their GLO gene were under no selective pressure to keep it, is that all species which have lost their GLO gene have very different diets but all of them have diets rich in vitamin C
What would a diet poor in vitamin C be considering that "everything else" makes it? I guess root vegetables? It feels like, if anything, this would imply a GLO gene decay more often than has happened, no?
By bluGill 2025-10-2819:37 That is probably a question for a nutritionist not me. My understanding is Grains, root vegetables, and meat are all low in vitamin C. Likely other things as well. But I'm not a nutritionist (I've read enough that I think I'm right here, but not enough to state it with confidence), so take the above with plenty of salt.
By marbro 2025-10-2817:32 [dead]
Most definitions of the word vitamin are not specific to humans. Wikipedia talks about "organisms", Britannica about "higher animal life", Webster about "most animals and some plants"
By lxgr 2025-10-2818:14 What is and isn't a vitamin by definition varies from species to species.
I don't agree. As with everything, it requires care. Taking a multivitamin and thinking you're good to go is delusional.
For most people just eating a good balanced diet and they are good to go. There are a few with genetic/biological issues and they need more - ask your doctor. Vitamin D is one that modern lifestyles likely don't get enough of and so probably worth it - again talk to your doctor.
If eating a "good balanced diet" were easy/normal, we'd have close to zero disease. Supplements are definitely a way to get as close as possible to balance when day to day food intake is chaotic.
By OutOfHere 2025-10-3014:09 ErikCorry, bluGill and others like them get people killed with their exceedingly harmful assertions. It is pointless to argue with them since they're here to spread harm, also probably working for big pharma. The best that one can do is ask the reader to find the evidence for themselves.
By bluGill 2025-10-2821:10 there is no reason to think a good diet will prevent disease, nor that supplements will help in most cases. Good diet will prevent some disease, but disease is natural in the environment and good diet is mostly your immune system has what it needs to fight it off after you get it.
By OutOfHere 2025-10-2815:58 [flagged]
By supportengineer 2025-10-2817:541 reply How do you feel about vaccines and Tylenol?
By IAmBroom 2025-10-2818:27 Uncalled for. GP is pointing out that the fact the human body can produce Vitamin D means it is not a vitamin.
vi·ta·min /ˈvīdəmən/ noun any of a group of organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body.
