A deficiency in the sunshine vitamin (which is actually a hormone) has been correlated with a higher susceptibility to many chronic diseases, including cancer. A vitamin D deficiency is also associated with an increased risk for autoimmunity and a susceptibility to chronic infections.
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods. Low levels of vitamin D can be the result of many factors, these include – eating foods fortified with synthetic vitamin D2 instead of D3; not eating enough of the few vitamin D-rich foods; use of conventional sunscreen, which blocks the skin from making vitamin D from natural sunlight; insufficient time in the sun; or using soaps on the skin that strip the key microbiota that help us synthesize Vitamin D from our skin.
Ultraviolet B light reaching the skin is needed to synthesize vitamin D3 – which is the active precursor form of vitamin D. Vitamin D obtained from sun exposure, food, or supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol.
There are two food forms of vitamin D – the synthetic vitamin D2 (ergocalciferol) and the naturally occurring in more potent form, vitamin D3 (cholecalciferol). Vitamin D2 was first produced in the early 1920’s and is derived from irrigated ergosterol, a substance extracted from a mold called ergot that grows on rye and wheat. This process was patented and licensed to pharmaceutical companies which led to the development of a medical preparation of vitamin D2 called Viosterol. Vitamin D2 is now found in most fortified milks, cereals, and vitamins. It has less bioactivity than a naturally occurring vitamin D3 which is found in the highest concentrations in cod liver oil, cold water fish – like salmon, sardines, mackerel,and herring. It is also found in butter and egg yolks.
Studies suggest that vitamin D may be able to activate its receptor only with direct cooperation of vitamin A. The role of food synergies should not go unrecognized nor should we continue to isolate and extract vitamins and other compounds from food. Instead, we need to focus on the foods themselves. While cod liver oil, mackerel, and salmon contain both vitamin A and D3, eating a whole food based diet provides the body with the synergistic access to the nutrients it needs.
Vitamin D has many roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation. Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D.
Vitamin D also promotes calcium, absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone. It is needed for bone growth and bone remodeling. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Together with calcium, vitamin D also helps protect older adults from osteoporosis.
It is estimated that up to 95% of the US population is deficient in vitamin D.