Suffer from continuous colds? Try vitamin D3


Do you suffer continuously from colds? Do you cough every night in bed? Do you go from one course of antibiotics to the next? According to immunologists at the Karolinska Institutet in Sweden, you may be able to increase your resistance to infectious diseases by taking a high-dose vitamin D3 supplement.

Vitamin D & immune system
Vitamin D does more than just strengthen your bones. Vitamin D3 – vitamin D is really a hormone – also improves the quality of muscle tissue and keeps fat percentages low, and it improves the immune system. Epidemiological and in-vitro studies have shown that a high level of vitamin D in the blood protects against colds, tuberculosis, and maybe even against HIV.

That’s why the Swedes wanted to investigate how people with frequent respiratory tract infections would react to a course of vitamin D. They gathered a group of 124 subjects, and got half of them to take 4000 IE vitamin D3 every day. The researchers used Vigantol, produced by Merck. The other half of the group were given a placebo.

Every day the subjects completed a questionnaire about their health. They kept note of whether they had been coughing, had a runny nose, ear infection, whether they felt unwell, and whether they were using antibiotics. The researchers used this data to calculate a ‘composite infectious score’.

The first figure below shows how the supplementation more than doubled the concentration of vitamin D3 in the subjects’ blood.

The second figure shows that during the course of a year vitamin D3 reduced the infectious score. The line to look at is the one joining up the points. The score of the placebo group is set at 1. The longer supplementation continued, the better the subjects in the experimental group were protected against infections.


The figure above shows the effect of supplementation on the likelihood of contracting one of the five aspects that the researchers were looking at. Most noticeable is the effect of the vitamin supplementation on antibiotic use. The subjects in the vitamin D group were three times less likely to use antibiotics than the subjects in the placebo group.

Supplementation with vitamin D3 reduced the average infectious score in this study by 47 points, or 23 percent. That is not clinically relevant: the reduction would need to be 30 percent for this to be the case. Nevertheless the researchers think that vitamin D3 is interesting for people who suffer from continuous colds.

“We base this line of reasoning on the fact that a reduction of 47 points per patient can be translated into 47 days with cough, 23 days with ear and sinus symptoms, or 9 days with cough, sinus and ear symptoms together with malaise and antibiotics”, the Swedes write.

“In addition, our data indicate that vitamin D3 supplementation reduces the odds of taking antibiotics by approximately 60% in patients with frequent respiratory tract infections. Thus, supplementation with vitamin D3 could provide a novel strategy to reduce antibiotic use among high consumers and indirectly prevent the emerging epidemic of bacterial resistance.”

Vitamin D3 supplementation in patients with frequent respiratory tract infections: a randomised and double-blind intervention study.


Low serum levels of 25-hydroxyvitamin D(3) are associated with an increased risk of respiratory tract infections (RTIs). Clinical trials with vitamin D(3) against various infections have been carried out but data are so far not conclusive. Thus, there is a need for additional randomised controlled trials of effects of vitamin D(3) on infections.

To investigate if supplementation with vitamin D(3) could reduce infectious symptoms and antibiotic consumption among patients with antibody deficiency or frequent RTIs.

A double-blind randomised controlled trial.

Karolinska University Hospital, Huddinge.

140 patients with antibody deficiency (selective IgA subclass deficiency, IgG subclass deficiency, common variable immune disorder) and patients with increased susceptibility to RTIs (>4 bacterial RTIs/year) but without immunological diagnosis.

Vitamin D(3) (4000 IU) or placebo was given daily for 1 year.

The primary endpoint was an infectious score based on five parameters: symptoms from respiratory tract, ears and sinuses, malaise and antibiotic consumption. Secondary endpoints were serum levels of 25-hydroxyvitamin D(3), microbiological findings and levels of antimicrobial peptides (LL-37, HNP1-3) in nasal fluid.

The overall infectious score was significantly reduced for patients allocated to the vitamin D group (202 points) compared with the placebo group (249 points; adjusted relative score 0.771, 95% CI 0.604 to 0.985, p=0.04).

A single study centre, small sample size and a selected group of patients. The sample size calculation was performed using p=0.02 as the significance level whereas the primary and secondary endpoints were analysed using the conventional p=0.05 as the significance level.

Supplementation with vitamin D(3) may reduce disease burden in patients with frequent RTIs.
PMID: 23242238 [PubMed] PMCID: PMC3533016