Vitamin D is more a hormone than a vitamin. It is made (like many hormones) from cholesterol and exposure to sunlight. The healthiest and safest way to procure an adequate supply of vitamin D is through limited exposure to sunlight. Recently, vitamin D has been linked to the prevention of polyps and cancer of the colon and rectum. In smoggy cities where people receive little sunlight there is a high incidence of colon cancer.
Vitamin D is involved in normal cell growth and maturation, and so may play a part in cancer prevention. Laboratory experiments show that vitamin D can inhibit the growth of human prostate cancer and breast cancer cells. Lung cancer and pancreatic cancer cells may also be susceptible to the effects of vitamin D.
Vitamin D is believed to suppress melanoma growth and also to reduce the occurrence of oestrogen-sensitive breast cancers, colorectal cancer and prostatic cancer. An active form of vitamin D, known as vitamin D3 is being considered as a possible treatment to slow the spread and growth of osteosarcoma, melanoma, colon cancer and breast cancer.
Colorectal Cancer and Skin Cancer
Studies are beginning to indicate that people who have a high vitamin D intake are less likely to develop cancer of the colon or rectum than people with a low vitamin D intake. Vitamin D in small amounts is also thought to be protective against skin cancer, particularly malignant melanoma.
Prostate Cancer
Various studies throughout the world indicate that there may be a reduced risk of prostate cancer in men with high vitamin D levels. Vitamin D is found naturally only in fish and fish-liver oils. However, it is also found in milk (vitamin D-fortified). Cooking does not affect the vitamin D in foods. Vitamin D is sometimes called the ‘sunshine vitamin’ since it is made in your skin when you are exposed to sunlight. If you eat a balanced diet and get outside in the sunshine at least one and a half to two hours a week, you should be getting all the vitamin D you need.
A particular form of vitamin D is believed to inhibit the growth of prostate cancer cells in laboratory tests. Fructose, the sugar found in fruits, stimulates the production of this form of vitamin D. Eating plenty of fruits is generally associated with lower levels of prostate cancer.
Good sources of vitamin D include beef, butter, cheese, cod liver oil, cream, egg yolks, halibut liver oil, kippers, liver, mackerel, milk, salmon, sardines, shrimp, sunflower seeds and tuna.
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