Fiber is a carbohydrate the body can’t digest or absorb. Soluble fiber dissolves in water to form a gel that slows digestion and can help lower cholesterol and blood sugar.

It's in good supply in avocados, carrots, apples, oats, bananas, barley, and citrus fruits. Insoluble fiber — in bran, 100% whole wheat flour, nuts, beans, cauliflower, potatoes, and green beans — powers the movement of food through your digestive system.

Most plant foods contain some of both.

We've long known that a happy gut depends on a daily supply of fiber, but new insights reveal that a fiber-rich diet promotes weight loss and helps lower the risk of osteoporosis (and not just because you're taking pressure off joints as you lose weight).

A recent study in the journal Nutrition & Metabolism found that ditching animal foods helped participants lose 13 pounds over 16 weeks. The researchers say that's from an automatic reduction in fat and calories, plus increased fiber intake that makes the body burn more calories to digest food.

Another study in the American Journal of Managed Care found that the more dietary fiber a person eats, the less likely they are to develop osteoarthritis. That's because a high-fiber diet helps cool inflammation. It took 15 grams to 26 grams of dietary fiber daily to protect joint health.

One cup of cooked black beans delivers 15 grams; a cup of cooked split peas, 16 grams; a cup of artichoke hearts, 14 grams; and a cup of raspberries or blackberries, around 8 grams.

For great high-fiber recipes, check out "The What to Eat When Cookbook."