Despite the name, dietary Vitamin D is a fat-soluble hormone essential for the absorption of calcium in our body. The active form of vitamin D is Vitamin D3—derived from cholesterol. Vitamin D is stored within fat cells, which is why we need adequate fat consumption for dietary absorption.
It was Dr. Daniel Whistler who made the initial association between severe vitamin D deficiency and soft bones – rickets—in the 17th century. However it was not until the 1900s that major breakthroughs were made in the study of rickets and its causative factors. It took a little while longer for scientists to realise that humans synthesize vitamin D in the skin in response to exposure to sunlight. One famous, rather strange, experiment involved irradiating a small piece of excised skin with UV light then feeding to rats, these rats were found to be protected against rickets. We now understand the critical importance of vitamin D, some even calling it the ‘elixir of life’.
Functions in our body
Healthy bones
As mentioned, vitamin D is required for optimum calcium absorption. Calcium is essential for proper bone and teeth mineralization. Without sufficient calcium, the bone density is compromised resulting in thin, brittle and easily fractured bones. Severe deficiency can cause softening of the bones, in adults this is known as osteomalacia and in children, rickets. Osteoporosis, a bone condition in older adults is also a result of insufficient bone mineralization as a result of vitamin D deficiency.
Immune system
Vitamin D has important roles in both the innate and adaptive immune system. Our innate immune system is our primary defence system against foreign pathogens. Our adaptive immune system acts as a secondary defence system where it fights pathogens based upon memory from previous encounters. Both work together to effectively fight infections and diseases. Increasing evidence is suggesting that a compromised adaptive system in winter months due to vitamin D deficiency is the cause of flus. Vitamin D is indeed a powerful immune stimulant against tuberculosis. Administration of vitamin D rich cod liver oil resulted in significant improvements in TB symptoms in patients.
Cancer Prevention
Vitamin D deficiency is linked with increased risk of a number of cancers including colon, breast and prostate cancer. Vitamin D does this by by preventing cancers from creating their own blood vessels for survival, as well as preventing cancer cells from dividing and spreading to other organs. Vitamin D also enhances calcium release in the body; this prevents cells from dividing again and induces cell death in unstable cells. All these mechanisms work together to prevent cancer.
How to prevent deficiency?
Vitamin D is also known as the ‘sunshine’ vitamin, because the action of UV light from the sun on the skin is needed for its conversion to its active form. Hence it is important to ensure that you maintain daily exposure to the sun for 15 – 20 minutes with hands and legs exposed. Moreover you should eat foods rich in vitamin D such as oily fish (salmon, cod, sardines), eggs, cheese, milk and yogurt. In the cases of severe deficiency ask your doctor about appropriate supplements, and your required daily dosage.
References
1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470481/
3. http://www.ncbi.nlm.nih.gov/pubmed/2541158/
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