The risks associated with vitamin D deficiency

A deficiency of this vitamin is suspected of being involved in different illnesses such as bone diseases, but also in cardiovascular diseases, multiple sclerosis or even cancer. All of these possible risks need to be clarified and confirmed: “For some diseases, the relationship between cause and effect has been clearly demonstrated: this is the case with rickets in children or Osteomalacia in adults”, explains Professor Kolh. In addition, vitamin D deficiency is also present in individuals who develop multiple sclerosis. Studies show that, not merely is vitamin D deficiency a simple correlation or even a consequence of this illness, but vitamin D deficiency is indeed a risk factor with regard to onset of the disease because it is present long before the appearance of symptoms.

On the other hand, according to different scientific literature journals, the intake of vitamin D supplements or vitamin D + calcium has not yet proven its efficiency with regard to the prevention of cancers, cardiovascular disease, Parkinson’s disease or diabetes. The authors of this study point out that a reduction in vitamin D levels can nonetheless be considered as a marker for a deterioration in health involving a large number of illnesses but without necessarily being the cause of them.
Even more surprising is the fact that, given typical recommendations, these supplements do not yield any concrete benefits in terms of prevention of fractures (of the hip in particular) nor for the treatment of osteoporosis among the elderly, with the exception of those individuals who live in a retirement home.

What is the role of supplements?

Increasing vitamin D intake through diet or exposure to sunlight could be possible solutions but this is difficult in our country: “Vitamin D intake in food is mainly in oily fish or in fortified foods such as margarines. But in Belgium, the legislation does not allow vitamin D to be added to a large number of foods unlike Canada or the United States for example where this is common practice. As for vitamin D intake through sunlight, it is evident that, even though we sometimes have sunny summers, intense exposure to sunlight or sunbeds is not advisable given the risk of melanoma…”

As a result, the study which has just been published (1) sought to understand the impact of vitamin D supplement intake on the vitamin D status of the population. For the momentno supplementation protocol exists for the general population who are in good health: “This study demonstrated that 23.1% affirmed that they took supplements of the vitamin; yet 99.8% of all the individuals studied were above the values recommended by the IOM, that is to say, 600 IU/day, No such recommendation exists for the general population but only for individuals suffering from a disease”, continues Professor Kolh.

A population apart?

Yet is seems that a proportion of the population might not derive any benefit from vitamin D supplements: individuals who are obese. The study shows an inverse relationship between concentrations of 25(OH) D in the blood and the BMI (body mass index) of the individual: the more overweight the person, the less vitamin D the individual has. And this applies whether or not the said individual takes supplements. “This could be explained by the fact that vitamin D is fat-soluble, and that it is therefore stored in adipose tissue, thus making it less available for hydroxylation… This signifies that individuals who are obese should receive higher doses of the vitamin”.

So the message of this study is that, even when supplements are being taken, our vitamin D requirements are not necessarily being satisfied. Should the wider population therefore be encouraged to take supplements? As we have seen, the benefits of vitamin D intake can be disappointing: “Through this study, we have demonstrated that there is a growing interest in vitamin D from a scientific point of view, that its role with regard to calcium and bone mineralisation should be increased and the preventive role it can play with regard to a whole series of illnesses. While its physiological role with regard to bones has been well-documented, the question remains as to whether vitamin D and/or calcium supplements will have an effect on bones. It all depends on what section of the population is targeted: is it worthwhile for pregnant women, menopausal women or women who are breast-feeding, as well as those who have has breast cancer to take 800 IU/day in supplements. For the remainder, if vitamin D does not reduce the risk of developing certain diseases, it does not increase the risk either. There is still a lot of research to be done in this area because if it acts on the expression of certain genes in the cells, we can conclude that this might have an impact on the functioning – normal or abnormal – of the cells in question…”, continues Professor Kolh.

(1) Hoge A., Donneau AF, Streel S., Kolh P., Chapelle JP, Albert A., Cavalier E., Guillaume M., Vitamin D deficiency is common among adults in Wallonia (Belgium, 51°30′ North): findings from the Nutrition, Environment and Cardio-Vascular Health study. Nutrition Research 35 (2015) 716 – 725