This year's sweet potato harvest is showing up on market and store shelves. It's a timely arrival for a holiday meal staple.

If medical and health experts had their way, however, we would be eating more sweet potatoes year-round.

This is according to two separate studies by the Center for Science in the Public Interest. Both rated the sweet potato as by far the most nutritional U.S. vegetable easily beating out both broccoli and spinach.

"In part, though, it's because natural components in sweet potatoes help the body resist some of our most common deadly diseases. So, overall, the sweet potato is close to being a superfood," according to Ted Carey, a horticulture expert with Kansas State Research and Extension.

Among the many groups that now rank the sweet potato as one of the world's top health foods are the Mayo Clinics, U.S. Centers for Disease Control and Prevention, George Mateljan Foundation and Bill & Melinda Gates Foundation.

Fresh sweet potatoes are the best buys because they come with their skin. The skin has nutrients of its own. Plus, it helps make a sweet potato's fiber content equivalent to the fiber in a bowl of oatmeal.

Sweet potatoes also are a great source of the antioxidants vitamin E and beta-carotene (vitamin A). Antioxidants bolster the human immune system. They provide protection against cancer, heart disease and stroke. Some evidence suggests they even help delay the progression of Alzheimer's disease.

Sweet potatoes also are basically fat- and cholesterol-free, setting them apart from other vitamin E sources such as nuts, avocados and vegetable oils. In addition, sweet potatoes have a low glycemic index, which is important to both diabetics and carbohydrate counters for maintaining steady blood-glucose levels.

A low glycemic index means you digest them slowly. Another benefit of that, of course, is they make you feel full longer.

Sweet potatoes provide from one-third to one-half of the recommended daily allowance of vitamin C, another immune system booster.

Sweet potatoes also are an important source of vitamin B6 and iron. They contain folate, a B vitamin that's essential for cell growth and reproduction. They're among the top three food sources of potassium, which helps maintain normal blood pressure and the body's heart and nerve functions.

It doesn't hurt, too, that the sweet potato is fairly low in calories. And, it's virtually sodium-free, all-in-all a great choice for eating year-round.

For more information on holiday foods, see my Living Well blog at www.swktalk.com/livingwell.