TUESDAY, March 24, 2015 (HealthDay News) -- In more good news for those who fill up on bran cereal and quinoa, a new study suggests that older people who eat a lot of whole grains may live longer than those who hardly ever eat them.
Even the obese and sedentary appear to gain a benefit, the researchers added.
People should "eat more whole grains and reduce intake of refined carbohydrates," said study co-author Dr. Lu Qi, an associate professor of medicine at Harvard Medical School in Boston.
Qi added that eating more grains may even help people lose weight: "There is no evidence that [a diet rich in] whole grain increases calorie intake, and it may lower it," he said.
The finding does have limitations -- almost all participants were white, for example -- and it doesn't directly prove that eating lots of whole grains caused people to live longer.
In the study, researchers looked at whole fiber -- the whole seed of grain that's used in grain products like bread and cereal.
The researchers tracked almost 370,000 people in the United States from the mid-1990s, when they took surveys, through the year 2009. They were all members of AARP and aged 50 to 71. The study excluded tens of thousands of people with conditions such as cancer, heart disease and stroke, meaning that the results don't apply to older people as a whole.
After adjusting their statistics so they wouldn't be thrown off by high or low numbers of certain types of people, the researchers found that those who ate the most fiber were 17 percent less likely to die during the study period than those who ate the least. However, the risk of death during the study was low overall: About 12 percent (just over 46,000) of the people died during the study period.
Those who ate the most fiber were more likely to be educated, less likely to be obese and less likely to smoke than those who ate the least, the study found. They also ate much less red meat, on average. But the life span benefit held up even when researchers adjusted their statistics to eliminate the impact of factors such as obesity and poorer health.
The researchers also found signs that whole grains lowered the risk of premature death from lung disease and diabetes. More consumption of the cereal fiber inside whole grains, meanwhile, translated to fewer deaths and lower levels of cancer and diabetes.
How much whole grain might a person need to reap this benefit? A lot. The researchers defined heavy eaters of whole grains -- those with the greatest life span benefits -- as those who ate 34 grams of whole grains for every 1,000 calories they consumed per day. For a person on a 2,500-calorie diet, that's 85 grams: the equivalent of five slices of whole wheat bread or 5 cups of whole-grain breakfast cereal.
Those defined as eating the least whole grain consumed about 4 grams per 1,000 calories per day, or 10 grams for a person on a 2,500-calorie diet. That's fewer grams than are in half a cup of oatmeal (16 grams).
One expert noted that switching over to whole grains could make a big difference.
"National survey data indicate that the current average intake of dietary fiber is only 16 grams, so increasing dietary fiber intake to the recommended more than 30 grams a day could significantly impact public health," said Dr. Yunsheng Ma, an associate professor in the division of preventive and behavioral medicine at the University of Massachusetts Medical School in Worcester, Mass.
"Foods high in fiber are predominantly protective foods high in micronutrient density, such as fruit, vegetables, whole grains, nuts, seeds, and legumes," Ma added. "There is no upper limit that has been set for dietary fiber intake per day."
Ma, who's familiar with the new research, wrote a study published earlier this year that linked fiber consumption to lower weight, blood pressure and blood sugar levels.
Why might whole grains be so good for a person's health? Study co-author Qi said they may work by lowering three things: food intake overall, levels of "bad" cholesterol, and inflammation.
The study is published in the March 24 edition of BMC Medicine.
For more about whole grains, visit the Harvard School of Public Health.