Walnuts are the oldest known tree food, with records of their consumption dating back to 7000 B.C.

Merchants traveling the Silk Road transported them between Asia and the Middle East. The ancient Romans called them Juglans regia, or "Jupiter's royal acorn."

More recently, nutritional science has identified what makes them so good for you. Some studies show walnuts help control diabetes and lessen diabetes-related nerve pain. Other research finds they're beneficial to brain health and lower LDL cholesterol levels. And a new study clarifies why they're so good for your heart.

Published in the Journal of the American College of Cardiology, the research followed 600 healthy older adults for two years. Some consumed 30 to 60 grams (1 to 2 ounces) of walnuts per day; others followed a standard diet without any walnuts.

When the researchers measured levels of 10 well-known inflammatory biomarkers, they found that people on the walnut diet had reductions of up to 11.5% in six of them, including interleukin-1B, which is often a target of pharmaceutical interventions when treating heart disease.

The tamping down of inflammatory markers likely comes from walnuts’ super-serving of the omega-3 fatty acid called alpha-linolenic acid (ALA). Just about 1 ounce of the nuts provides 2.5 grams of ALA.

And according to a study in the American Journal of Clinical Nutrition, every gram of ALA you eat per day lowers your risk of dying from heart disease by 10%.

So go nuts — about 12-14 walnut halves a day should do it.