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May 13, 2005

Vitamin D gaining importance in cancer

Topics: Medical Science News

From osteoporosis to multiple sclerosis and cancer, vitamin D continues to be of interest to researchers and clinicians.

Vitamin D is formed in the skin of animals and humans by the action of short-wave ultraviolet light - the so-called fast-tanning sun rays. Precursors of vitamin D in the skin are converted into cholecalciferol, a weak form of vitamin D3, which is then transported to the liver and kidneys where enzymes convert it to 1,25-dihydroxycholecalciferol, the more potent form of vitamin D3. In vitro and animal studies indicate that vitamin D may have anti-cancer benefits, including against progression and metastasis, against a wide spectrum of cancers. Supporting an anti-cancer effect of vitamin D is the ability of many cells to convert 25(OH)D, the primary circulating form of vitamin D, into 1,25(OH)(2)D, the most active form vitamin D. Researchers at M.D. Anderson wrote recently in a March 2005 article that Vitamin D has potent anti-tumour properties, and that calcitriol [1,25(OH)2D3], the hormonal derivative of vitamin D3, is an antiproliferative and prodifferentiation factor for several cell types, including human squamous cells of the head and neck.

Although no epidemiologic studies have directly measured vitamin D concentrations or intakes on risk of total cancer incidence or mortality, higher rates of total cancer mortality in regions with less UV-B radiation, and among African-Americans and overweight and obese people, each associated with lower circulating vitamin D, are compatible with a benefit of vitamin D on mortality. In addition, poorer survival from cancer in individuals diagnosed in the months when vitamin D levels are lowest suggests a benefit of vitamin D against late stages of carcinogenesis. The only individual cancer sites that have been examined directly in relation to vitamin D status are colorectal, prostate and breast cancers. For breast cancer, some data are promising for a benefit from vitamin D but are far too sparse to support a conclusion. The evidence that higher 25(OH)D levels through increased sunlight exposure or dietary or supplement intake inhibit colorectal carcinogenesis is substantial. The biologic evidence for an anti-cancer role of 25(OH)D is also strong for prostate cancer, but the epidemiologic data have not been supportive. Although not entirely consistent, some studies suggest that higher circulating 1,25(OH)(2)D may be more important than 25(OH)D for protection against aggressive, poorly-differentiated prostate cancer. A possible explanation for these divergent results is that unlike colorectal tumors, prostate cancers lose the ability to hydroxylate 25(OH)D to 1,25(OH)(2)D, and thus may rely on the circulation as the main source of 1,25(OH)(2)D. The suppression of circulating 1,25(OH)(2)D levels by calcium intake could explain why higher calcium and milk intakes appear to increase risk of advanced prostate cancer. But do they?

Inconsistencies still remain. Yet clarity is begining to emerge regarding vitamin D and a host of diseases:

(United Press International via MedlinePlus)

Vitamin D has so many healthy effects, U.S. researchers said people may not be getting enough to receive the full benefit.

The May issue of Mayo Clinic Health Letter said recent studies have found elderly women taking vitamin D had better leg strength and fewer falls, and 93 percent of patients ages 10-65 with musculoskeletal pain were vitamin D deficient.

Researchers are looking at the vitamin's role in disease, given that lower incidences of prostate, colon and breast cancers, multiple sclerosis, and type I diabetes are found in regions that receive higher amounts of direct sunlight throughout the year -- which exposes skin to thousands of international units of vitamin D.

The Food and Nutrition Board of the Institute of Medicine recommends adults through age 50 take 200 IU of vitamin D daily. The recommendations go up for older adults to 400 IU for ages 51 to 70, and 600 IU for those over age 70.

Mayo researchers suggested the best levels for overall health may be higher -- perhaps in the range of 800 to 1,000 IU a day. - End item.

To which I add(re: the supplementation of 800 to 1,000 IU/day), along with a quality combination multiple vitamin and mineral supplement and only after discussing your nutritional and supplement regimen with your physician and/or a knowledgeable health professional(the health food store and Internet gurus are not usually knowledgeable health professionals). Many folks fail to realize that vitamins function in a complex network of reactions and co-factor relationships, and taking "too much of one and/or not enough of the other" can be worse than none at all!

Suggested readings:

Promoting general health during androgen deprivation therapy (ADT): A rapid 10-step review for your patients.

href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15867263">Autocrine metabolism of vitamin D in normal and malignant breast tissue.

Polymorphisms of vitamin D receptor gene protect against the risk of head and neck cancer.

Cross posted at Hyscience

Posted by Richard at May 13, 2005 12:35 PM

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