|Answer:||A while thereare hundreds of studies that show that beta-carotene (the vitamin A in carrots), either in food or supplements, reduces cancer risk, there are two studies that found a slightly increased incidence in lung cancer in heavy smokers supplementing betacarotene. These studies also found a decrease in risk among non-smokers. A recent study may explain why.
Researchers from the National Cancer Institute in the US gave people who had had colon cancer betacarotene on its own, vitamin C and E on their own,
or all three versus a placebo. Each vitamin, on its own, or in combination, reduced incidence of colo-rectal polyps - except for smokers taking beta-carotene on its own. They had an-increase in polyps, which is an indication of increased risk for cancer of the colon.
So, what does this mean? Smoking delivers a massive amount of cancer-causing oxidants. A ' team' of antioxidants, including beta-carotene, C and E, normally disarms these. When an antioxidant, such as beta-carotene, disarms an oxidant it becomes an oxidised, in other words becomes an oxidant in its own right. This is almost certainly what' s happening by giving smokers beta-carotene on its own. However, the antioxidants ' oxidised' by smoking are then effectively ' reloaded' , or turned back into good guys, by other members of the antioxidant team. Provided beta-carotene is given with other antioxidants such as vitamin C and E the effect is only positive. It' s a case of ' united we stand, divided we fall' .
So, beta-carotene, either in foods that contain other vitamin C and E (that is, in fruits and vegetables) or in antioxidant supplements containing vitamin C and E, will reduce your risk of cancer. However, it may be wise notto supplement beta-carotene on its own if you are a smoker.