Orthomolecular Medicine News Service, August 20, 2008
VITAMIN A : Cancer Cure or Cancer Cause?
Media Tells a One-Sided Story
(OMNS, August 20, 2008) Vitamin A "pushes," "promotes," and even "incites" cancer growth, say the headlines! Is this yet another instance of vitamin bashing, or are you supplement-takers killing yourselves? Let's take a look.
A few researchers are claiming that vitamin A, in a test-tube experiment, will "push" stem cells to change into cells that can build blood vessels. This, they say, may increase cancer. So when "structures similar to blood vessels developed within the tumor masses grown in culture," they concluded that vitamin A promotes carcinogenesis. (1) That is a bit of a leap. An in vitro (test-tube) project is far from clinical proof. Even the study authors admit "vitamin A is known to be necessary for embryonic development precisely because it helps to 'differentiate' stem cells, pushing them to become required tissue."
There is an anti-cancer drug that specifically acts by blocking the breakdown of retinoic acid, derived from vitamin A. This approach has been found to be "surprisingly effective in treating animal models of human prostate cancer. . . Daily injections of the agent VN/14-1 resulted in up to a 50 percent decrease in tumor volume in mice implanted with human prostate cancer cells. . . No further tumor growth was seen during the five-week study." (2) It seems that when cancerous tumors have more vitamin A available, they shrink. And there is a good reason tumors shrink. "Keeping more retinoic acid available within cancer cells. . . redirects these cells back into their normal growth patterns, which includes programmed cell death. . . This potent agent causes cancer cells to differentiate, forcing them to turn back to a non-cancerous state." So vitamin A seems to induce positive, healthy, cell changes. Indeed, this is why vitamin A derivatives are already in wide use to fight! skin cancer. Vitamin A fights cancer. It does not "push," "promote," or "incite" it.
Sensational warnings and outright misstatements that natural vitamin A may "incite" cancer actually serve to incite newspaper readers and television viewers. Upon closer examination, a "vitamin promotes cancer" study often has the appearance of being conducted to prove an intended point. As the authors fuel fears about vitamin A, they also give away their goal, in their own words stating that "these findings open a new door to drug development." New marketing avenues for the development of patentable vitamin A-like drugs are a commercial opportunity that the pharmaceutical industry has not overlooked.
A vitamin A derivative "could protect against lung cancer development in former smokers," says another report. (3) Significantly, the vitamin A derivative is used "combined with alpha-tocopherol (vitamin E), in order to reduce toxicity known to be associated with 13-cis-RA (the vitamin A derivative) therapy." This illustrates why orthomolecular (nutritional) physicians do not use high doses of vitamin A by itself, but rather give it in context with other important, synergistic nutrients. A baseball team entirely made up of pitchers might get a lot of strikeouts while in the field, but not hit many home runs when at bat. All nutrients are needed in a living body. Vitamin A is an essential part of the team.
Here is an example: "A study published in the Journal of Nutritional Biochemistry found that administering both vitamin A and vitamin C to cultured human breast cancer cells was more than three times as effective than the administration of either compound alone (since) the combination of the two vitamins inhibited proliferation by 75.7 percent compared to untreated cells. . . The ability of retinoic acid (vitamin A) to inhibit tumor cell proliferation is well known, although its mechanism has not been defined. The authors suggest that the synergistic effect observed in this study is due to ascorbic acid's ability to slow the degradation of retinoic acid, thereby increasing vitamin A's cell proliferation inhibitory effects." (4) Vitamin C helps vitamin A do its work even better, a clear team advantage.
Doctors' experience and clinical evidence both show that vitamin A helps prevent cancer. This has been known for a long time. "The association of vitamin A and cancer was initially reported in 1926 when rats, fed a vitamin A-deficient diet, developed gastric carcinomas. . . The first investigation showing a relationship between vitamin A and human cancer was performed in 1941 by Abelsetal who found low plasma vitamin A levels in patients with gastrointestinal cancer." (5) Moon et al reported daily supplemental doses of 25,000 IU of vitamin A prevented squamous cell carcinoma. And, de Klerk and colleagues reported "findings of significantly lower rates of mesothelioma among subjects assigned to retinol. . . Studies that use animal models have shown that retinoids (including vitamin A) can act in the promotion-progression phase of carcinogenesis and block the development of invasive carcinoma at several epithelial sites, including the head and neck and lung." (5) The Linus ! Pauling Institute adds, "Studies in cell culture and animal models have documented the capacity for natural and synthetic retinoids to reduce carcinogenesis significantly in skin, breast, liver, colon, prostate, and other sites." (6).
National data from the American Association of Poison Control Centers repeatedly fails to show even one death from vitamin A per year. (7) Vitamin A is very safe. However, pregnancy is a special case where prolonged intake of too much preformed oil-form vitamin A might be harmful to the fetus, even at relatively low levels (under 20,000 IU/day). Interestingly enough, you can get over 100,000 IU of vitamin A from eating only seven ounces of beef liver. Have you ever yet seen a pregnancy overdose warning on a supermarket package of liver?
A lack of vitamin A, especially during pregnancy, and in infancy, poses far greater risks. Deficiency of vitamin A in developing babies is known to cause birth defects, poor tooth enamel, a weakened immune system, and literally hundreds of thousands of cases of blindness per year worldwide. This is why developing countries safely give megadoses of vitamin A to newborns to prevent infant deaths and disease. (8)
There will always be people bent on believing that vitamins must be harmful, somehow. For them, it only remains to set up some test-tubes to try to prove it. Such has been done with other vitamins, perhaps most notably a famous if silly experiment that claimed that vitamin C promoted cancer. The study, reported in New Scientist, 22 September 2001, was a prime example of sketchy science carelessly reported. The article would have readers uncritically extend the questionable findings of a highly artificial, electrical-current-vibrated quartz crystal test tube study, and conclude that 2,000 milligrams of vitamin C can (somehow) do some sort of mischief to human DNA in real life. If two thousand milligrams of vitamin C were harmful, the entire animal kingdom would be dead. Our nearest primate relatives all eat well in excess of 2,000 mg of vitamin C each day. And, pound for pound, most animals actually manufacture from 2,000 to 10,000 mg of vitamin C daily, right inside their! bodies. If such generous quantities of vitamin C were harmful, evolution would have had millions of years to select against it. Same with vitamin A. If it "promoted" cancer, every animal eating it would get cancer.