There always seems to be conflicting information published when it comes to vitamins and how they affect our body. I always trust answers that are given to me by Dr. Steve Chaney*, my friend and mentor as I study nutrition. Dr. Chaney recently posted the following information in his newsletter, Tips from the Professor. This information is a little scientific but still easy enough to read, and understand why some research isn’t as useful as other research articles.
In the information below you’ll notice that the first research was done with children living in extreme cold conditions, therefore not getting ample exposure to the sun. While the second research was done in the summer, in a warm climate, where the subjects were getting plenty of vitamin D from the sun. That doesn’t seem to me to be a very fair assessment on the efficacy of vitamin D and colds.
Here is what Dr. Chaney wrote regarding two published research articles that appear to be saying opposite results regarding the benefit of vitamin D and colds:
The first study, which showed that vitamin D was effective, was done with 250 Mongolian school children during the winter. At the beginning of the study their blood levels of 25 hydroxy vitamin D, the accepted measure of active vitamin D in the bloodstream, was only 7 ng/dL – a level that is clearly deficient.
Supplementing their diet with 300 IU of vitamin D per day during the winter increased their blood levels of
25 hydroxy vitamin D to 19 ng/dL – a level that is borderline adequate – and decreased their susceptibility to colds and flu by a highly significant 50%.
The second study (Murdoch et al, JAMA, 308: 1333-1339,
2012) was equally robust, but it was conducted in New Zealand starting in the summer. The average blood level of 25 hydroxy vitamin D at the start of this study was
29 ng/dL – a level that’s considered borderline optimal. The lowest average blood level of 25 hydroxy vitamin D in the placebo group in mid-winter was 20 ng/dL – slightly higher than the highest average blood level of 25 hydroxy vitamin D in the previous study.
In this study supplementation with high levels of vitamin D had no effect on the incidence of colds and flu in this population.
Unfortunately, this study did not report the percentage of the population who had inadequate blood levels of 25 hydroxy vitamin D. Nor did it report the effect of vitamin D on the incidence of colds and flu in the subset of the population that started with inadequate levels of 25 hydroxy vitamin D.
In short, the difference between these two studies is pretty clear cut, and the conclusions are obvious.
Vitamin D clearly reduces the incidence of colds and flu in people who have inadequate blood levels of 25 hydroxy vitamin D, but has no affect on the incidence of colds and flu in people who have optimal levels of
25 hydroxy vitamin D.
In summary, the headlines that you read about both studies are correct once you put them in the proper perspective. However, those headlines that tell you that you are wasting your money by supplementing with vitamin D are a little misleading. Whether vitamin D reduces your risk of colds and flu depends on your blood levels of 25 hydroxy vitamin D.
So, the important question for you is which of these two groups do you fall in? Some experts have estimated that anywhere from 20 to 40% of the US population in northern areas of the country have inadequate blood levels of 25 hydroxy vitamin D during the winter – and these percentages may even higher for certain ethnic groups.
Of course, what you really want to know is if you are one of those people who may need more vitamin D to fend off colds and flu this winter.
To start with there are certain common characteristics that predispose you to low blood levels of 25 hydroxy vitamin D. These are:
– little Sun exposure or excessive use of sunscreen during the summer month
– residence in the northern third of the United States
– inadequate consumption of vitamin D containing foods
– dark skin color
If you have two or more of these risk factors you might want to consider supplemental vitamin D – especially during the winter months.
However, there is also a genetic component. Some people who have none of these risk factors still have low 25 hydroxy vitamin D levels. The reason for this is not fully understood at present, but if you have frequent colds and flu during the winter months, you may want to have your blood levels of 25 hydroxy vitamin D measured and consider vitamin D supplementation if they are suboptimal
To Your Health!
Dr. Stephen G Chaney
After reading this report, I hope you have decided that you would like to consider adding vitamin D to your health program. I know that I am!
Wishing you well,
*Steve Chaney PhD, just retired from being the Professor of Biochemistry and Nutrition at UNC Chapel Hill. Both he and his wife, Suzanne, have been actively involved with Shaklee for 35 years. Shaklee is the oldest nutritional company in the USA, and is stringent at keeping all the products pure, and all raw ingredients organic.