Bowl of Oatmeal a Day May Be Key to a Longer Life, Major Study Finds

— -- Eating a small bowl of oatmeal may be the secret to a longer life, a large new study suggests.

Harvard University researchers reviewed two large studies that followed more than 100,000 people who were periodically quizzed about what they ate and how they lived for more than 14 years. It turns out the folks who ate at least 33 grams of whole grains daily -- equivalent to a bowl of oatmeal -- cut their risk of premature death by 9 percent compared to those who barely ate whole grains at all, according to findings published Monday in JAMA Internal Medicine.

The risk of dying from heart disease was slashed by 15 percent, though eating whole grains didn't seem to lower the risk of dying from cancer, the study showed.

"Whole grains may protect the heart by lowering blood sugar and insulin levels," said Qi Sun, an assistant professor with the Harvard School of Public Health and one of the study's authors. "This type of property could improve insulin resistance to lower the risk of cardiovascular disease and diabetes."

Sun added that weight loss and other healthy nutrients may add to the health benefits of whole grains. He also said the studies may not have yielded enough information about cancer to draw any conclusions. Previous studies have demonstrated a lower risk of colorectal cancers with high consumption of foods made from grains where the germ and bran have been left intact, he noted.

Though the study teased out factors such as family history, lifestyle, smoking and other dietary habits, it did have some limitations. Sun said that for one, it was an observational study versus a controlled trial. Additionally, the biggest difference in death risk was between the two extremes -- those who ate a lot of whole grains versus those that ate very little -- but wasn't much different for those who ate somewhere in between.

However, Sun pointed out that each additional 28-gram increase in whole grains per day led to even greater protection.

"It could be a dose response where you have to eat a certain amount to get the benefits and going above that would be even better," he said.

To keep up with breaking health and medical news, follow ABC News Health on Twitter.