D3: Effects Beyond the Bone

It’s also known as “vitamin of the Sun”, because most of it is synthesized in the skin under the effect of ultraviolet solar radiation. We all know that it is associated with good bone health, but it is not limited to that. What would you say if you heard that this vitamin can help you recover faster from a cold or can prevent diabetes mellitus and other diseases? Endocrinologist Dr Giovanna Spina reveals the many faces of this miraculous vitamin!


We all know the beneficial effect of vitamin D in maintaining normal calcium levels and in the metabolism of phosphorus. This means that the health and quality of bone is directly related to vitamin D. Its effects, however, are not limited to the bone. Sufficient quantities in the body can ensure good disposition and vitality, protects from winter infections (as it reinforces the immune system) and contributes to the body’s overall good health.

Its effects beyond the bone are demonstrated by the fact that vitamin D receptors are found in many tissues of the human body. As the endocrinologist Dr Giovanna Spina says, “vitamin D is bound to receptors (VDR) found in various tissues and, in addition to calcium homeostasis, it also affects cellular development. Receptors for this vitamin have been found in various tissues and cells, such as prostate, breast, intestinal, cardiac, pancreatic, brain, thyroid, adrenal, keratin, bone and cancer cells”. As the expert notes, recent research has shown that vitamin D can affect the function of the immune system as vitamin D receptors have been found in activated macrophages, lymphocytes and dendritic cells.


► Other effects and uses:

ü  In autoimmune diseases: “The presence of receptors in activated T and B lymphocytes is associated with the vitamin’s immunomodulatory activity. Therefore, it might have a use in the management of autoimmune diseases, in organ transplantations and in multiple sclerosis”, explains the expert.

ü  In psoriasis: Vitamin D has been used successfully in the treatment of psoriasis.

ü  In the prevention of diabetes mellitus: Sufficient amounts of vitamin D have been associated with a decrease in the risk of occurrence of type 1 diabetes mellitus.

ü  In the prevention of cardiovascular episodes: “Vitamin D insufficiency is associated with increased cardiovascular risk, especially in patients with hypertension (1). According to the Framingham Heart Study, patients with reduced vitamin D levels have a two-fold higher risk for cardiovascular events”, notes Dr Spina. The same conclusions regarding the beneficial effect of vitamin D on the prevention of ischemic episodes and cerebrovascular accidents were reached in a recent study which determined that those who ingested lower amounts of dietary vitamin D had 22-27% greater chances of suffering a stroke.

ü  In pregnancy: Reduced vitamin D levels during pregnancy appear to cause problems with dental enamel and are associated with increased risk of caries in children.

ü  In immune system strengthening: Lack of vitamin has been associated with increased risk of flu during the winter.



Where can we obtain this vitamin? More than 90% of vitamin D is produced by the effect of solar radiation on substances present in the skin (sterols).

“Production of vitamin D is also higher in the midday hours than early in the morning or late in the evening. Furthermore, we have higher vitamin D levels in the summer. Production of the vitamin depends on radiation intensity, skin color and age. In the elderly, for example, vitamin D concentration is reduced by 30% because the elderly are usually less exposed to the sunlight”, explains Dr Spina, but this doesn’t mean that vitamin insufficiency is a problem only in the elderly. Reduced sunshine in winter and extensive use of UV-blocking sunscreen prevent the production of vitamin D from the body.

The remaining 10% of vitamin D that the body needs is obtained from food. As Dr Spina, explains, the most important foods that contain this valuable vitamin are fish (mostly salmon, codfish, herring, sardine and tuna), egg yolk, beef, liver and dairy products, but she stresses that “dairy products contain small amounts of vitamin D, insufficient to cover the body’s needs”.


Which people have greater need for vitamin D?

In addition to the elderly, who have lower exposure to sunshine and therefore synthesize smaller amounts of vitamin D, another population group which can benefit significantly from a vitamin D supplement are the obese. As Dr Spina explains, “obesity has been linked to reduced vitamin D levels, possibly because of the fact that the vitamin is stored primarily in the adipose tissue of obese people and does not circulate freely. This is perhaps the reason for which people with reduced vitamin D levels have a higher risk for type 2 diabetes mellitus. Another mechanism, which is being investigated, involves the existence of a gene which causes obese people to have lower vitamin D levels”. Weight loss can restore normal levels of the vitamin, thus reversing the conditions associated with obesity in two ways: through the beneficial effects of vitamin D and through controlling the fundamental etiology of the problems, which is excess weight. Finally, one of the major reasons for vitamin D insufficiency nowadays is the prolonged and extended use of sunscreen products.



who is who

Dr Giovanna Spina is an endocrinologist. She was born in Palermo, Italy, in 1958. She studied medicine and is a professor at the University of Athens. She maintains a private practice and is head of the Endocrinology Dept at the MEDIFIRST clinic. She is a regular member of the Hellenic Endocrine Society of and of the Hellenic Diabetes Association.

42, Andromachis str., Kallithea, Greece, tel. +302109530178, mobile +306932347276, e-mail:



  1. Suzanne Judd, Vin Tangpricha, Vitamin D Deficiency and Risk for Cardiovascular Disease, Circulation. 2008 January 29; 117(4): 503–511.