High-fiber diet tied to lower odds of early death
NEW YORK (Reuters Health) - People who eat a lot of fiber every day might be less likely to die prematurely from a range of illnesses -- including heart disease, cancer, and infection -- a new study suggests.
The benefits of fiber in promoting weight loss, lowering cholesterol, and protecting against heart disease have been well established by previous studies. However, the finding that fiber may also prevent other common killers is a new and interesting one, researchers say.
"The results from this study suggest that fiber may have broader health benefits than what has been found before," Dr. Frank Hu, who studies nutrition at the Harvard School of Public Health in Cambridge, Massachusetts, told Reuters Health. Dr. Hu wrote an editorial accompanying the study in the Archives of Internal Medicine.
While some of the benefits shown in the current study still need to be confirmed with further research, Hu said, "the bottom line is that fiber should be a staple in our diet, and we should strive to eat as much fiber as possible."
Fiber is commonly found in whole grains, fruits, vegetables, and beans. The U.S. Department of Agriculture (USDA) recommends that adult women eat about 25 grams of fiber each day and men about 38 grams.
To get an idea of how much that is, consider these examples. According to the USDA's National Nutrition Database (available online at bit.ly/hP7Wz8), a half cup of boiled lentils contains about 8 grams of fiber. A half cup of raw almonds has nearly 9 grams. A cup of cooked oatmeal has 4 grams. A half cup of pitted prunes has about 6 grams.
In the current study, Dr. Yikyung Park of the National Cancer Institute in Bethesda, Maryland and her colleagues tracked about 400,000 people, all members of the American Association of Retired Persons (AARP). In 1995 and 1996, when they were between 50 and 71 years old, each participant filled out a survey about eating habits. The researchers also gathered other information, including physical activity levels, weight, and whether or not the participants were smokers. From the food survey, Park and her colleagues calculated how much fiber on average each person in the study consumed on a daily basis.
Using national databases of deaths and causes of death, the authors were able to determine which of the original study participants died, and from what causes, in the following years. On average, records spanned 9 years from when participants filled out their original questionnaires.
The researchers found a wide range in the amount of fiber that people consumed. In the one-fifth of participants who ate the least fiber, men averaged 13 grams a day, women 11 grams. In the one-fifth with the highest fiber intake, men consumed an average of 29 grams of fiber daily, and women an average of 26 grams.
Comparing those two groups, the researchers found that people who ate the most fiber were 22 percent less likely to have died of any cause during the study than people who ate the least, when they took into account age as well as health and lifestyle factors.
That pattern remained when the results were broken down by cause of death: people who ate the most fiber were less likely to die of cardiovascular disease, infectious diseases, and respiratory disease -- which includes pneumonia and asthma -- than those who consumed the least fiber. For men only, eating more fiber was also linked to a lower risk of dying from cancer.
Overall, fiber had a greater protective effect when it came from grains -- such as brown rice, wheat, and lentils, for example -- rather than fruits, vegetables, or beans. The reason could be that whole grains also have other ingredients, including vitamins and minerals, that have been shown to prevent disease, Hu said.
Fiber may help prevent against disease in a number of ways. Dr. Yunsheng Ma, who studies diet and heart disease at the University of Massachusetts Medical School in Worcester and was not involved in the current study, told Reuters Health, "Fiber could help with maintaining normal bowel bacteria. Some studies say that if you eat different food, that affects the bacteria in the bowel and it could be related to different diseases."
In addition, fiber attaches itself to potential cancer-causing agents, to increase the likelihood that they will be eliminated from the body, Park told Reuters Health.
Despite these benefits, the study doesn't prove that fiber directly prevents premature death. Although the authors factored in things like exercise and body weight in their analysis, "people who eat high-fiber (diets) in general tend to have a healthier lifestyle," Park said, and that may still be responsible for part of the link to fewer deaths from a range of diseases.
Also, the researchers had to depend on people in the study to describe their diets accurately, because the filled-out surveys provided the only clues to what participants usually ate.
And the results, especially the findings about infectious and respiratory diseases, still need to be confirmed in future studies, researchers said.
Still, the message is for people to make sure they're getting the recommended amount of fiber each day, preferably from whole grain products, Hu said.
SOURCE: bit.ly/g19Dqx Archives of Internal Medicine, online February 14, 2011.
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