Are vitamin supplements necessary to get daily allowance as suggested by scientists?
Scientists' understanding of the benefits of vitamins has rapidly advanced, and it now appears that people who get enough vitamins may be able to prevent such common chronic illnesses as cancer, heart disease and osteoporosis, according to Drs. Robert H. Fletcher and Kathleen M. Fairfield of Harvard University, who wrote JAMA's new guidelines.
The last time JAMA made a comprehensive review of vitamins, about 20 years ago; it concluded that normal people shouldn't take multivitamins because they were a waste of time and money. People can get all the nutrients they need from their diet, JAMA advised, adding that only pregnant women and chronically sick people may need certain vitamins.
That was at a time when knowledge about vitamins was just beginning to expand. Now, our access to meaningful data allows us to understand the needs of current day Americans. The role that low levels of foliate, or folic acid, play in neural tube defects, for instance, was not known, nor was its role as a major risk factor for heart disease.
Many doctors have been telling their patients for years to take vitamins. Nearly 1 out of 3 Americans take multivitamins and many of them are afraid to tell their doctor for fear he or she would disapprove. But researchers hope that JAMA's endorsement will result in more people reaping health benefits of a daily vitamin.
Health experts are increasingly worried that most American adults do not consume healthy amounts of vitamins in their diet, although they may be getting enough to ward off such vitamin deficiency disorders as scurvy, beriberi and pellagra. Almost 80 percent of Americans do not eat at least five helpings of fruits and vegetables a day, the recommended minimum amount believed to provide sufficient essential nutrients. Humans do not make their own vitamins, except for some vitamin D, and they must get them from food to prevent metabolic disorders.
RDA's Being Revised
"It's just wonderful that JAMA is publishing this information and this recommendation," said Dr. Jeffrey Blumberg, chief of antioxidant research at Tufts University's Jean Mayer USDA Human Nutrition Research Center on Aging. "It's nice to see this change in philosophy that's saying we can make public health recommendations based on this really compelling set of data."
Blumberg said the JAMA recommendations are also important because they underscore a growing concept among nutrition experts that the recommended daily allowances, or RDAs, for many vitamins are set too low. RDAs essentially were established to prevent symptoms of vitamin deficiency disorders, he said. But there is growing evidence that higher levels of many vitamins are necessary to achieve optimum health, he said. The National Academy of Sciences, which sets RDAs, is revising its recommendations based on the new evidence.
Even people who eat five daily servings of fruits and vegetables may not get enough of certain vitamins for optimum health, Fletcher said. Most people, for instance, cannot get the healthiest levels of foliate and vitamins D and E from currently recommended diets, he said.
Nutritional Knowledge Lacking
Fletcher and Fairfield said efforts to get people to eat healthier diets have not been very successful. The nation's doctors need to upgrade their knowledge about nutrition and tell patients to take multivitamins, he said. "Physicians are inadequately trained in nutrition," she said. "Everybody talks about it and tries to do something about it, but so far only a few places do it well."
The Harvard researchers reviewed more than 150 studies to determine the health benefits of nine vitamins. They concluded that suboptimal levels of folic acid and vitamins B6 and B12 are a risk factor for heart disease, neural tube defects and colon and breast cancer; low levels of vitamin D contribute to osteoporosis and fractures; and inadequate levels of the antioxidant vitamins A, E and C may increase the risk of cancer and heart disease.