A diet rich in fiber may decrease a person's overall risk of death over a nine-year period, according to a new study. Dietary fiber may help prevent death from cardiovascular disease, and well as infectious and respiratory diseases, the researchers say.

The researchers examined the diets of more than 219,000 men and 168,000 women who initially answered a food survey questionnaire in 1995 and 1996. Those who ate the most fiber (29.4 grams per day for men and 25.8 grams per day for women) were 22 percent less likely to have died than those who ate the least amount of fiber an average of nine years later.

Men and women who consumed the most fiber were eating about the amount the United States Department of Agriculture recommends people eat, said study researcher Yikyung Park, of the National Cancer Institute in Rockville, Md.

The results held true even after the researchers took into account factors that might influence a person's risk of death, including physical activity, smoking, alcohol consumption and body mass index (BMI).

The study adds to a growing body of work showing dietary fiber, which makes up the edible part of plants that can't be digested, is good for you. Previous work has suggested fiber lowers the risk of cardiovascular disease , obesity and some cancers. But the new study is one of the largest to look at the link between fiber and overall risk of death, the researchers said.

"It's not new to us in the nutrition field," said Katherine Tallmadge, a spokesperson for the American Dietetic Association, who was not involved in the study. "We've known for a long time, this is important stuff," Tallmadge said. "It's exciting when more and more research comes out showing these links, confirming what we think is correct about...the importance of a plant based diet."

However, Tallmadge said, it's important to eat foods that are naturally fiber-rich, such as whole grains , fruits, vegetables and beans. There is no evidence that processed foods fortified with fiber, such as foods that list all-purpose flour or inulin as sources of fiber, provide the same benefits.

"It's probably not the fiber alone that is causing the health benefits," Tallmadge said. "It's all those vitamins, minerals and compounds in those foods, which are naturally fiber-rich, contributing to these health benefits."

The study is published online today (Feb. 14) in the journal Archives of Internal Medicine.

Why is fiber good?

Fiber has been shown to decrease levels of fat in the blood, improve blood sugar levels, lower blood pressure and improve bowel movements, the researchers said. Fiber is also thought to promote the excretion of carcinogen compounds, Park, said.

In addition, fiber may decrease inflammation in the body. Inflammation is an immune response and can be beneficial when your body is fighting off infection, but chronically high levels of inflammation are known to play a role in certain conditions, including asthma and cardiovascular disease.

"Increased inflammation leads to greater tissue destruction and disease severity," wrote Lawrence de Koning, and Frank Hu, of the Harvard School of Public Health in Boston, in an editorial accompanying the study. "Therefore, the intake of whole grains might plausibly reduce the severity of a number of different diseases," they wrote.

In the study, dietary fiber reduced the risk of dying from cardiovascular disease, infectious and respiratory disease over the nine-year study period by 24 to 56 percent for men, and 34 to 59 percent for women.

The study found a reduced risk of dying from cancer only for men. This could be because fiber only lowers the risk of specific cancers, such as head and neck cancer and esophageal cancer, which are more common in men. Future studies should further examine this link, the researchers said.

Whole grains vs. fruits and vegetables

Fiber from grains had the strongest benefit in terms of reducing risk of death in the study. But people should still get their fiber from fruits and vegetables as well, Tallmadge said.

But earlier work found a link between eating fruits and vegetables and a decreased risk of death, Tallmadge said.

Pass it on: A diet rich in fiber may decrease the risk of death from all causes.

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