Wednesday, October 14, 2009

Can Skin Cancer Be Prevented With Vitamin A? Can Skin Cancer Be Prevented With Vitamin A?

Vitamin A may be important for skin cancer protection. The skin and mucosal cells (cells that line the airways, digestive tract, and urinary tract) function as a barrier and form the body's first line of defense against infection. Retinol (vitamin A) and its metabolites (e.g. beta carotene which is converted to vitamin A) are required to maintain the integrity and function of these cells. (Proceedings of the Nutrition Society. 1999).

In 1999 Researchers from the University of Michigan reported that ultraviolet irradiation from the sun causes a major loss of retinoic acid receptors in skin cells. They concluded that ultraviolet irradiation causes a vitamin A deficiency that may have harmful effects on skin function, contributing to premature aging of the skin and the creation of skin cancer. (Nature Medicine 1999; 5(4): 418-422).

In 2001 researchers from The University of Texas, Baylor College of Medicine and the University of Arizona looked at the effects of sun exposure and retinoic acid (vitamin A) receptors in skin cells.

The study examined these effects in relation to squamous skin carcinogenesis (SCC) (the process by which normal cells are transformed into cancer cells).
They observed a progressive decrease in retinoic acid (vitamin A) receptors from normal skin to precancerous skin progressing to invasive skin SCC (squamous cell carcinogenesis).
Their results indicate that the suppression of retinoid (vitamin A) receptors occurs early in the precancerous stage and is associated with progression of squamous skin carcinogenesis (the creation of cancer). (Cancer Res, 61: 4306-10, 2001).

Swedish researchers, reporting in the journal Experimental Dermatology in 2003, used cultured normal human keratinocytes and melanocytes (skin cells) to examine the effects of UV irradiation on the main retinoid receptors in the human skin.
The keratinocyte is the major cell type of the epidermis (outer layer of skin), making up about 90% of epidermal cells. Melanocytes are cells located in the bottom layer of the skin's epidermis.
The authors concluded that a depletion of vitamin A and retinoid receptors, together with other factors, by ultraviolet (UV) irradiation might seriously interfere with retinoid (vitamin A) signalling and therefore promote future tumour development, especially in keratinocytes (see above). (Exp Dermatol. 2003 Oct;12(5):563-71).

In 1993 Edes and a colleague at the Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, Missouri, reported in a review that exposure to benzopyrene, a carcinogen (cancer causing substance) causes vitamin A depletion in exposed tissues.
They noted that the effect is apparent while on a vitamin A sufficient diet but significantly, without a decline in serum (blood) Vitamin A. In other words, benzopyrene depleted vitamin A even when the diet was adequate in the vitamin, and this depletion is not apparent in blood tests.

Benzopyrene also known as benzo(a)pyrene is found in coal tar, in automobile exhaust fumes (especially from diesel engines), tobacco smoke, and in charbroiled food. Recent studies have revealed that levels of benzopyrene in burnt toast are significantly higher than once thought, although it is unproven whether burnt toast is itself carcinogenic. (Wikipedia).
Reviewing the studies to date they observed that although these studies involved dietary intake of benzopyrene, it would be realistic to surmise cigarette smoke exposure would have a similar effect. (Ann N Y Acad Sci. 1993 May 28;686:203-11; discussion 211-2. Review).
by Kevin Flatt

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