SUNSHINE IS ESSENTIAL FOR VITAMIN D SYNTHESIS IN THE SKIN
Introduction
In a previous post, the possible importance of vitamin D in the prevention of common cancers, heart and autoimmune diseases, rickets, osteomalacia (bone pain and muscle weakness), diabetes, multiple sclerosis (MS), and depression was described (see, Vitamin D, Part 1: “Early Warning: Dull Days Of 2012 Will Have Increased Widespread Vitamin D Deficiency Epidemic in 2013”). Subsequently, knowledge of the role of vitamin D in disease resistance has significantly increased and important advances made are briefly described in this post.
Vitamin D deficiency
Remember that the diet only provides a limited amount of vitamin D. The main source is from ultraviolet B (UVB) in sunlight, with 2 or 3 exposures to the sun, 20-30 minutes weekly, sufficient for vitamin D synthesis in the skin. It was originally thought that vitamin D deficiency was confined to Northern regions of the World, like Northern Europe, with insufficient sunshine for effective vitamin D synthesis for 6 months from October to April. Surprisingly, Vitamin D deficiency has also now recently been found to be common in hot countries like Australia and Brazil where many people avoid the sun and use sun blockers.
Present status of studies on vitamin D
The list of diseases/conditions associated with vitamin D deficiency continues to grow and now includes diabetes, pregnancy problems, lack of foetal growth, neurological disorders, susceptibility to tuberculosis/leprosy and sickle cell blood disease.
However, evidence finally proving beyond any doubt a relationship between vitamin D and any disease condition is difficult to obtain. This is because proof has to be provided sampling human subjects and such studies are notoriously difficult to carry out with large populations. This is due both to the large variability in the diets and physiological conditions of the subjects used as well as in differences in the analytical techniques adopted by the researchers. A further complication is that the development of any disease condition may involve many environmental and genetic factors acting in concert.
Vitamin D deficiency and multiple sclerosis
One example of problems involved in proving beyond doubt the role of vitamin D deficiency in disease development is with multiple sclerosis (MS). Thus, the link between vitamin D deficiency and MS was first suggested in 1974 but is still is not unequivocally accepted.
Studies have shown a correlation between patients with MS living in temperate and Northern countries and low vitamin D levels. The problem is, however, that in these studies the control “normal” people also have vitamin D deficiency without having MS making any conclusions difficult to justify. Such studies indicate that other environmental and genetic factors are probably involved in the development of MS (Pierrot-Deseilligny and Souberbielle, Therapeutic Advances in Neurological Disorders, 2013:
http://tan.sagepub.com/content/early/2013/01/22/1756285612473513).
Molecular studies on vitamin D deficiency and disease
Real progress in understanding and confirming the role of vitamin D in the disease process comes from recent studies showing the interaction of vitamin D directly with the genes and DNA. Thus, exciting new techniques for studying the interaction of nutrients, such as vitamin D, with the genes in the cells have been developed.
It is estimated that vitamin D may influence the activity of 5% of the human genes via a receptor, the vitamin D receptor, attached to the DNA of the cell and controlling the action of the genes. These receptors were found to be concentrated near genes involved in auto-immune diseases such as MS, rheumatoid arthritis, and cancers like colorectal cancer (Wellcome Trust, press release, “Vitamin D found to influence over 200 genes, highlighting links to disease”, 24th August 2010).
Similarly, in a study of the correlation between vitamin D levels and gene expression in Norwegian women, it was shown that vitamin levels correlated with the expression of genes associated with immunity and inflammation (Olsen and colleagues, European Journal of Clinical Nutrition, volume 67, pages 773–778, 2013).
These studies illustrate how the effects of nutritional factors, such as vitamin D, can modulate the immune system and influence the disease process.
Conclusion
The molecular studies, outlined above, are a very important development in our understanding of the role of vitamins and minerals in the body. At last, it is possible to examine, at the gene level, the influence of these factors on the physiology of the human body. Progress can now be made to resolve the controversy and uncertainty that exists over the use of nutritional supplements.
It’s Your Life: End the Confusion from Inconsistent Health Advice
It's Your Life: End the Confusion from Inconsistent Health Advice 