If you read our recent three-part series about nature's healthiest superfoods, today's news about walnuts rated tops among all ground and tree nuts for their high quality and combination of antioxidants probably wasn't surprising.

What will surprise you, as it did me, was how few walnuts it takes to make an impact on your health: Try seven. A handful of walnuts has nearly double the amount of antioxidants, compared to any same quantity of any other nut commonly eaten by consumers, says University of Scranton chemist Dr. Joe Vinson whose study rank-ordered nine different nuts for their health value.

Another eye-opening discovery about walnuts from Dr. Vinson: The antioxidants contained in walnuts were up to 15 times more potent than Vitamin E, a fat-soluble vitamin that protects your body from free radicals.

What makes walnuts such a potent source of antioxidants? Just as you can lose out on the benefits of eating some foods -- the anti-cancer, anti-inflammatory component in broccoli won't form if the one enzyme needed to make it is destroyed due to overcooking -- too much heat reduces the antioxidant quality of most nuts, Dr. Vinson says. That's not a problem with walnuts because they're usually eaten raw.

You may be concerned about gaining weight due to the fat content of nuts, but the evidence doesn't warrant it. In fact, the results of a 2009 study in the American Journal of Clinical Nutrition showed higher nut consumption was associated with a slightly lower risk of obesity and weight gain, further suggesting eating nuts may help with weight control.

University of Scranton March 29, 2011

ScienceDaily March 28, 2011

Time/Healthland March 29, 2011

MSNBC.com March 28, 2011