Perils of too many vitamins

Your immune system has built-in mechanisms for protecting you from infections. But mega-doses of a popular vitamin may actually make immune cells forget how to fulfil some of their health-promoting functions. In a surprising study, researchers at the Department of Internal Medicine at Radboud University Medical Centre in Nijmegen, Netherlands, found that when you take too much vitamin A, you may compromise your immune system and make yourself more liable to becoming ill from a bacterial or viral infection.

The researchers believe that you should not take vitamin A supplements unless you have been shown to be severely deficient in a medical lab test.

"This study helps to explain the mechanisms of anti-inflammatory effects of vitamin A and by doing so opens the door to identifying novel ways to modulate the immune response and restore its function in situations in which it is dysregulated," says researcher Mihai G. Netea.

Usually, your immune system learns on the job. After you have become ill from an infectious pathogen, your immune system learns to recognize the defeated invader and is more prepared to quickly render it harmless if the same sort of pathogen invades again in the future. But lab tests at Radboud show that vitamin A can make the immune system forget this knowledge.

Instead, when microbes return to try to start another infection, the immune cells, after exposure to too much vitamin A, have to be taught all over again how to cope with the illness-producing organisms. The necessity for limiting your vitamin A intake is in sharp contrast to what occurs with vitamin D. Vitamin D helps strengthen immunity and research has shown that even if you take large doses of vitamin D, they hardly ever produce harmful effects. But you should go easy with vitamin A, and take these researchers' advice and avoid supplementing.

Instead just eat a well-rounded diet that includes vitamin A source foods to get the amount you need, starting with chicken liver, beef liver and eggs. Vegetables like sweet potatoes, carrots and spinach contain carotenoids that your body can convert into vitamin A.

If you'd like to find out how much vitamin A you should get in your diet, The National Institutes of Health provides detailed information, and also recommends that people get most of their nutrients from food instead of supplements.

- Easy Health Option