People who eat lots of whole grains are less likely than others to die of cardiovascular disease or cancer during long periods of follow-up, according to a new analysis of previous studies.

The American Heart Association recommends that at least half of the grains we consume be whole grains, like oats or oatmeal, rye, barley, corn or brown rice. Dietary Guidelines for Americans recommend three or more servings of whole grains per day, but most U.S. adults get less than one serving per day, the authors write.

It's well known that whole grain consumption can reduce risk of many chronic diseases, including cardiovascular diseases and colorectal cancer, said senior author Dr. Qi Sun of the Harvard T.H. Chan School of Public Health in Boston.

But there hadn't been a larger analysis of whole grain intake and overall death, Sun told Reuters Health by phone.

Researchers pooled the results of 14 long-term studies of whole grain intake and risk of death that involved a total of 786,076 people, including 97,867 who died during the studies. Almost 24,000 died of cardiovascular disease and more than 37,000 from cancer.

Ten studies took place in the U.S., three in Scandinavia and one in the U.K. All of the studies used questionnaires to estimate whole grain intake.

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People who ate the most whole grains were about 16 percent less likely to die of any cause during the study than those who ate the least, almost 20 percent less likely to die from cardiovascular disease and more than 10 percent less likely to die of cancer.

For every additional serving of 16 grams of whole grains, cardiovascular disease-related death risk declined by 9 percent and cancer death risk by five percent, as reported in the review in Circulation.

A half-cup of cooked brown rice, cooked oatmeal, or cooked 100 percent whole grain pasta, for example, or one slice of 100 percent whole grain bread, would be the equivalent of about 16 grams.

"Scientific evidence for the positive association between whole-grain cereal consumption and diminished risk of chronic diseases and mortality is rather strong, relevant and coherent," said Anthony Fardet of The University of Auvergne in France, who was not part of the new review.

Whole-grain nutrients are released in the digestive tract more slowly than in refined grains, and we tend to chew whole grains longer thus stimulating more satiety hormones, which is not the case with soft, sweetened, refined cereal-based foods, Fardet told Reuters Health by email.

"There's a pretty linear association between whole grain intake and mortality," Sun said.

Of course, everyone dies, but those who eat more whole grains have a lower risk of dying at a younger age, he said.

"There are many biological pathways that would explain why whole grains are beneficial," he said. Whole grains are high in fiber, which reduces unhealthy blood lipids and increases insulin sensitivity, which helps control sugar metabolism.

Although whole grain breads, pastas and brown rice products are readily available in stores, most Americans do not get enough whole grains, Sun said.