Feb. 14, 2011 -- Filling up on fiber -- particularly fiber from whole grains -- may reduce your risk of dying from heart disease, infections, and respiratory diseases, says a new study published online in the Archives of Internal Medicine.
Men and women who ate the most dietary fiber were 22% less likely to die from any cause when compared to study participants who ate the least amount of fiber. The protective effect came mainly from cereal fiber in grains, not other sources of fiber such as fruits and vegetables.
“Prior studies have focused on the relationship between fiber intake and cardiovascular disease, but few have examined the link between dietary fiber and mortality,” study researcher Yikyung Park, ScD, a staff scientist at the National Cancer Institute in Rockville, Md., says in an email. “Our analysis adds to the literature and suggests that dietary fiber is associated with a decreased likelihood of death.”
Fiber-rich diets help lower blood cholesterol levels and blood sugar levels, which may explain why it is considered heart-healthy. Exactly how fiber may reduce risk of death from lung disease and infections is not known, but these diseases tend to be inflammatory in origin, and fiber may have certain anti-inflammatory properties. Heart disease is also believed to be linked to inflammation.
Still, study authors caution, it could be that people who eat more fiber are healthier overall, and that this may be why they are less likely to die from all causes in the new study.
Park and colleagues analyzed data on 219,123 men and 168,999 women who completed a food frequency questionnaire in 1995 and 1996. During nine years of follow-up, 20,126 men and 11,330 women died. Risk of death was lower among study participants who ate the most fiber.
On average, men ate 13 to 29 grams of fiber per day, and women ate 11 to 26 grams. Overall, the risk of death from heart disease, infections, and respiratory diseases was reduced by 24% to 56% in men and by 34% to 59% in women who got the highest amounts of fiber in the study.
People who ate the most fiber tended to have higher education, a self-rated health status of good-excellent, a lower BMI, be physically active, and use menopausal hormone therapy (in women). They were also less likely to smoke, drink alcohol, or eat red meat. Nevertheless, even after adjusting for many of these factors, the association between survival and fiber intake remained significant.
“What is new and important about this study is that it examined multiple causes of death [while] most previous studies of fiber and mortality focused only on heart attack and stroke,” says Lawrence de Koning, PhD, a postdoctoral and clinical chemistry fellow at the Harvard School of Public Health in Boston. De Koning co-authored an editorial that accompanies the new study.
“The most interesting result was that dietary fiber was protective for respiratory disease and infections,” he tells WebMD in an email. “This was a big surprise. It was even more surprising that the effect appeared larger than for heart attack and stroke.”
"Eating more fiber, particularly fiber from grains, may be related to reduced risk of dying from many different types of diseases -- not just cardiovascular disease,” he says.
The new U.S. dietary guidelines recommend that at least half of all grains consumed be whole and unrefined. The refining process removes all the bran, which contains the fiber. The goal for fiber is 25 grams per day for women 28 grams per day for men, and as it stands, most of us fall short.
Boost Fiber Now: Here’s How
So how can you get more fiber in your diet?
“The easiest way to accomplish this would be to always choose 'whole grain' breads, cereals, and baked goods over 'white' or refined varieties,” De Koning says. Specifically, breads that list "100% whole wheat flour" as the first ingredient would be a good choice over ones that list “wheat flour" as the first ingredient, as this is likely refined white flour, he says.
“Another nice way to increase cereal fiber would be to eat cooked cereals such as steel cut oats at breakfast instead of cold ones,” he says.
The new study did not look at fiber supplements. “But it is unlikely that simply taking a fiber supplement would give the same benefit of as eating whole grains,” he says. “Whole grains are high in many health-promoting compounds that might not be present in a commercially produced fiber supplement. Some of these include antioxidants, which may help to prevent a runaway inflammatory response. It is this runaway inflammation that may be responsible for high mortality due to respiratory and infectious diseases.”
Neil Schachter, MD, professor of pulmonary medicine at Mount Sinai School of Medicine in New York City, reviewed the new study for WebMD.
"This is an impressive study, but it's certainly not definitive," he says in an email. "The data suggests that the amount of dietary fiber intake is associated with significantly lower mortality in this initially healthy group [and] both men and women had statistical benefits," he says. "The benefit was primarily seen in diets with grain (not fruits) as the source of fiber."
Schachter says the study's strengths are its large size and relatively long follow-up period. Its weaknesses include the fact that not all of the potentially relevant information about study participants was known to the researchers, including vaccination history and level of medical care -- all which could play a role in their mortality.