Despite past reports that Vitamin D, the sunshine vitamin, helps with upper respiratory tract infections (colds), researchers are now saying it does not help reduce how often or how severely we get colds, according to a new study in JAMA.

Background information in the study said that the link between insufficient levels of vitamin D and how likely a person is to catch a cold had previously not been scientifically proven.

Many studies that have been carried out on vitamin D and its benefits for respiratory health have produced conflicting results. Scientists at the University Hospital Leuven, Belgium carried out a study expecting to confirm the full benefits of high vitamin D levels on COPD (chronic obstructive pulmonary disease) symptoms and outcomes. Unfortunately, they found that vitamin D supplements make no difference to COPD symptoms or the risk of developing the disease.

However, some randomized, controlled trials have demonstrated the importance of vitamin D in protecting the airways. Researchers from Massachusetts General Hospital reported in August 2012 that respiratory infection risk in winter is lower among Mongolian children who take a daily vitamin D supplement, compared to their counterparts who do not.

The new trial, led by David R. Murdoch, M.D., from the University of Otago, Christchurch, New Zealand and his team, took place between February 2010 and November 2011. It involved 322 healthy adult participants who were given a first dose of 200,000 IU vitamin D3 normally, followed by 200,000 IU a month later, then 100,000 monthly (n = 161), or a placebo which was given in the same doses (n=161), for 18 months total.

At the start of the investigation, the mean 25-hydroxyvitamin D (25-OHD) level was 29 ng/mL. When the participants were taking vitamin D supplements, their serum 25-OHD levels were increased to over 48 ng/mL, and remained at this level. In the vitamin D group, 593 people experienced URTI episodes, while the placebo group had 611.

According to the experts, they did not detect any important differences in how many URTIs each patient experienced – the vitamin D group individuals had an average of 3.7, while the placebo group had 3.8. Both groups had an average of 12 days of symptoms per episode. The researchers found no difference in the intensity of episodes, or number of work days missed, due to symptoms.

The authors wrote:

“The main finding from this study is that a monthly dose of 100,000 IU of vitamin D3 in healthy adults did not significantly reduce the incidence or severity of URTIs. This result remained unchanged when the analysis included winter season or baseline 25-OHD levels. Further research is required to clarify whether there is benefit from supplementation in other populations and with other dosing regimens.”

Health care professionals, nutritionists, dietitians and alternative therapists have tended to presume that vitamin D protects people from colds and reduces symptom severity among those who become ill.

As mentioned earlier, scores of studies on respiratory infections and conditions have clearly demonstrated the benefits. Scientists from Queen Mary, University of London, reported in September 2012 that vitamin D can help patients with tuberculosis recover more quickly.

Written by Christine Kearney