Vitamin D is a fat-soluble vitamin. There are two major types of vitamin D found in food: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D3 is generated in the skin of animals by sun exposure. Vitamin D2 is the type of vitamin D added to milk and supplements. In the D2 form, vitamin D is not biologically active. In the body, vitamin D is converted to its biologically active form, 1,25-dihydroxyvitamin D. Vitamin D has many functions. It aids in the absorption of calcium and phosphorus and signals your kidneys to retain calcium. As a result, calcium won't be lost from your body. In addition, it is involved in the control of cell growth and death.

Vitamin D receptors can be found on prostate cancer cells. Receptors can be thought of as on and off switches. When a substance binds to its receptor, it causes an event to occur. In this case, when vitamin D binds to its receptor on prostate cancer cells, the event that occurs is the slowing of the cancer growth. This inhibition of growth occurs in normal and cancerous prostate cells. Sources of Vitamin D include:

• Sunlight: The UV rays stimulate the production of vitamin D in the body. Try to get 10 - 15 minutes of exposure per day two to three times per week and no more. (Too much sun exposure can cause skin cancer.)
• Fortified soy milk products and fortified nonfat milk.
• Dark green leafy vegetables: Spinach and broccoli
• Cereals: Dry or cereal grain bars
• Make sure the cereals are fortified with at least 40 IU, which is 10% of the RDA (recommended dietary allowance).

Recent studies have shown that vitamin D may play a major role in the treatment of the prostate cancer. A study by Ahonen and colleagues demonstrated that vitamin D deficiency increases the risk of prostate cancer progression. In the study, men with high levels of vitamin D had delayed the appearance of clinical prostate cancer by 1.8 years.

Animal and in vitro (in test tubes) studies have shown that 1,25-dihydroxyvitamin D (the biologically active form of vitamin D) slows the growth of prostate cancer. A study from the University of Pittsburgh Cancer Institute shows that 1,25-dihydroxyvitamin D inhibited growth in a metastatic line of prostate cancer cells in both test tubes and animals.

• If you have inadequate vitamin D in your diet, take a multivitamin (such as Centrum). A multivitamin should contain 200 - 400 IU of vitamin D, which is all you need.

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