Do you faithfully take your vitamins everyday? Can popping vitamin pills prevent cancer?
The simple answer is NO, based on what we know so far. In fact, some vitamin supplements have even shown harm.
Beta Carotene: After the studies came out, researchers determined that in the lungs of smokers, the high doses of beta-carotene might have acted like a pro-oxidant (causing DNA damage) instead of an anti-oxidant. In two other studies of mostly non-smoking men and women, beta carotene didn't have an effect on cancer risk either way.
Selenium: A trial of selenium and skin cancer found no protection for skin cancer, but it did suggest a lower risk of prostate cancer, which led to another large trial. This second study, called SELECT, gave either selenium, vitamin E, both or placebo, to some 35,000 healthy men. It found no effect either way of selenium or vitamin E on prostate cancer.
Folate: Although folate is associated with a lower risk of developing colorectal (colon) cancer, a recent trial showed that in people who have had polyps removed, high doses of folic acid slightly increased the number and size of new polyps. What this suggests is that if the cancer process has already started, high dose supplements might feed the process.
Multivitamins: At least 50% of US adults take a vitamin supplement. The United States Preventive Task Force reviewed the evidence and concluded hat taking multivitamins (in adults) will not reduce the risk of cancer or other chronic diseases. Multivitamins contain several of the nutrients discussed above, though usually in lower doses than the trials.
Vitamin D: Although some observational studies provide some support for a role of vitamin D in colon cancer prevention, doses of 400 IU/day did not lower colon or breast cancer risk in a RCT. A new large trial testing vitamin D at higher doses (and fish oil) is underway, so results won't be out for several years. Vitamin D is hotly debated, and experts are understandably guarded about recommending any supplements to lower cancer risk until the evidence is solid.
Calcium: I've saved the best news for last. A large trial from the US showed that, in people who have had colorectal (colon) polyps removed, taking calcium lowers the risk that polyps will grow back by 15%. There is one hitch, though: men who consume or take high doses of calcium (say, >1,500 mg) may be at slightly higher risk of developing prostate cancer, according to some observational studies. For women, this is obviously not a problem. Until we know more, men may want to keep calcium intake between 800 mg and less than 1,500 mg. Supplements usually contain 500 mg, and a cup of milk contains 300 mg.
The important things to know:
1) Supplements are not the same as food. No supplement can fully replace a healthy diet.
2) More is not always better. Make sure to tell your health care provider about any supplements you are taking.
3) Supplements are not regulated by the FDA. That's right - no oversight. Given the fact that we know toxicities and overdoses can occur, and that some trials have shown harm from supplements, it's wise not to go overboard on supplements.
There may be other good reasons to take supplements, but at least for now, prevention of cancer is not one of them.
For more details, please click here: http://www.cancer.org/Cancer/News/ExpertVoices/post/2011/08/16/Will-a-vitamin-a-day-keep-cancer-away.aspx
