Question explored with the scientific record
role of vitamin d supplementaion in preventing influenza
The short version: the evidence on vitamin D for influenza is mixed, thin, and mostly from studies that did not test what you need to know.
The best evidence here is a 2010 prospective cohort study that found a threshold effect [1]. People with serum 25-hydroxyvitamin D above 38 ng/mL had far fewer lab-confirmed respiratory infections than those below it. The hazard ratio was 0.51 (95% CI 0.25–0.84, p<0.0001). That is a strong signal. But it is a cohort study, not a randomized trial. It shows association, not causation. People who maintain higher vitamin D levels may differ in other ways that matter.
The only randomized trial in the evidence directly tested the question [2]. It gave 2000 IU of vitamin D3 daily for 12 weeks to adults in winter. It found no reduction in incidence, duration, or severity of upper respiratory infections. The vitamin D group had 28 subjects with at least one URI; the placebo had 29. The p-value was 0.56. That is a null result from a trial that actually intervened.
| Study | Design | Key finding |
|---|---|---|
| Sabetta 2010 [1] | Prospective cohort, 198 adults | Threshold at 38 ng/mL: HR 0.51 for infection |
| Li-Ng 2009 [2] | RCT, 162 adults, 2000 IU/day | No reduction in URI incidence (p=0.56) |
The cohort study suggests a threshold worth reaching. The randomized trial says supplementing at 2000 IU does not prevent infection. The evidence does not tell you whether raising someone from deficient to sufficient changes the outcome, because the trial started with people whose mean baseline was already 64 ng/mL, well above the 38 ng/mL threshold. The trial tested adding more to people who were already adequate. That is a design that cannot answer the question a deficient person needs answered.
My call: the evidence does not support routine vitamin D supplementation for influenza prevention in people with adequate baseline levels. For people who are deficient, the question has not been properly tested. Confidence: moderate that supplementation at 2000 IU does not prevent infection in already-sufficient adults; low that it helps the deficient, because no adequate trial exists.
Sources examined 16
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Serum 25-Hydroxyvitamin D and the Incidence of Acute Viral Respiratory Tract Infections in Healthy Adults
Prospective cohort study in healthy adults linking monthly 25-hydroxyvitamin D levels to incidence of acute viral respiratory tract infections, identifying a threshold of 38 ng/mL above which infection risk and illness burden were substantially reduced, suggesting vitamin D opti…
DOI: 10.1371/journal.pone.0011088 -
A randomized controlled trial of vitamin D3 supplementation for the prevention of symptomatic upper respiratory tract infections
A double-blind randomized trial in adults during winter found that high-dose vitamin D3 (2000 IU daily) did not reduce incidence, duration, or severity of symptomatic upper respiratory tract infections over 12 weeks, despite raising serum 25-OHD levels.
DOI: 10.1017/s0950268809002404 -
Rethinking biotin therapy for hair, nail, and skin disorders
This study critically evaluates the use of biotin therapy for hair, nail, and skin disorders, highlighting its limited efficacy in individuals with normal biotin levels and the potential for interference with laboratory tests.
DOI: 10.1016/j.jaad.2018.02.018 -
Iron disorders can mimic anything, so always test for them
Iron disorders can mimic many conditions, so routine testing of iron status (ferritin, serum iron, transferrin saturation, TIBC) is advocated to avoid misdiagnosis and inappropriate supplementation.
DOI: 10.1016/0268-960x(92)90024-k -
The Effect of Ethoxyquin and Vitamin E Supplementation on the Display Life of Beef Steaks
This study evaluates the effects of dietary supplementation with ethoxyquin and varying levels of vitamin E on the display life and lipid oxidation of beef steaks, finding that vitamin E significantly improves display life without a synergistic effect from ethoxyquin.
DOI: 10.1111/j.1365-2621.2003.tb08290.x -
Impact of vitamin D supplementation during a resistance training intervention on body composition, muscle function, and glucose tolerance in overweight and obese adults
This study investigates the effects of vitamin D supplementation during a resistance training program on body composition, muscle function, and glucose tolerance in overweight and obese adults, finding that while vitamin D improved peak power, it did not significantly enhance le…
DOI: 10.1016/j.clnu.2012.08.014 -
MON-742 Less is More: Successful Conservative Management of PTH-Independent Hypercalcemia Due to Vitamin D Toxicity
A 25-year-old man with vitamin D toxicity presented with severe PTH-independent hypercalcemia that resolved within six days using conservative management with intravenous fluids, discontinuation of supplements, and oral hydration.
DOI: 10.1210/jendso/bvaf149.486 -
Effect of Calcium β‐Hydroxy‐β‐Methylbutyrate (CaHMB), Vitamin D, and Protein Supplementation on Postoperative Immobilization in Malnourished Older Adult Patients With Hip Fracture
This randomized controlled study investigates the effects of Calcium β-Hydroxy-β-Methylbutyrate (CaHMB), Vitamin D, and protein supplementation on wound healing, mobilization time, fat-free mass, muscle strength, and laboratory parameters in malnourished older adult patients wit…
DOI: 10.1177/0884533616629628 -
Microalbuminuria is a predictor of increased late in-hospital morbidity and mortality in patients with acute myocardial infarction
This study investigates the effects of short-term vitamin E administration on oxidative stress and endothelial function in patients after an acute myocardial infarction, finding no significant improvements in endothelial function or antioxidant effects.
DOI: 10.1016/s1567-5688(01)80340-8 -
Vitamin E (α-tocopherol) production by the marine microalgae Dunaliella tertiolecta and Tetraselmis suecica in batch cultivation
Batch-cultured marine microalgae Dunaliella tertiolecta and Tetraselmis suecica were studied to quantify alpha-tocopherol (a-T) production under varying light-per-cell conditions and nutrient statuses, revealing that light availability per cell does not limit alpha-tocopherol pr…
DOI: 10.1016/s1389-0344(03)00040-6 -
The Effect of Vitamin D Supplementation on Clinical and Laboratory Biomarkers in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-Analysis of Randomised Controlled Trials
A comprehensive systematic review and meta-analysis of randomized controlled trials assessing vitamin D supplementation in rheumatoid arthritis found significant improvements in serum vitamin D levels, pain (VAS), and CRP, but inconsistent effects on DAS28 and ESR across diverse…
DOI: 10.31138/mjr.090725.lar -
Ascorbic acid interference in the measurement of serum biochemical parameters: In vivo and in vitro studies
This study investigates the negative interference of ascorbic acid on serum biochemical tests, demonstrating that common doses of vitamin C can significantly affect urate and bilirubin measurements while not impacting glucose, triglyceride, and cholesterol tests.
DOI: 10.1016/j.clinbiochem.2005.11.011 -
Neuroprotective Effect of Vitamin E Supplementation in Patients Treated With Cisplatin Chemotherapy
This study evaluates the neuroprotective effect of vitamin E supplementation in reducing cisplatin-induced peripheral neurotoxicity in cancer patients, demonstrating a significant decrease in neurotoxicity incidence and severity without compromising the chemotherapy's efficacy.
DOI: 10.1200/JCO.2003.05.139 -
The effect of vitamin C supplementation in healthy dogs on antioxidative capacity and immune parameters
This study investigates the effects of vitamin C supplementation on antioxidative capacity and immune parameters in healthy dogs, finding limited impact on most measured outcomes.
DOI: 10.1111/j.1439-0396.2007.00774.x -
Vitamin B12-associated interactions between Mesorhizobium sp. TaiHu and Synechococcus sp. PCC 7002 revealed by multi-omics analysis
In a lab-built Syn7002–Mesorhizobium sp. TaiHu synthetic community, Mesorhizobium TaiHu provides vitamin B12 to Synechococcus sp. PCC 7002, boosting Syn7002 growth and triggering transcriptional changes that stabilize the consortium.
DOI: 10.1099/mgen.0.001665 -
Mechanisms and regulation of defensins in host defense
Defensins are cationic host defense peptides whose structural diversity underpins antimicrobial activity, immunomodulation, mucosal barrier maintenance, and regulation of gut microbiota, with implications for disease and potential nutritionally regulated therapies.
DOI: 10.1038/s41392-023-01553-x