If mushrooms see the light

This would be great news. Many people don't get enough sun exposure -- especially in the winter -- to produce adequate vitamin D, so dietary sources need to fill in the gap. But very few foods naturally contain vitamin D (egg yolks, liver, fish and the reviled cod liver oil) and only a few are permitted by the Food and Drug Administration to be vitamin D-fortified (milk and some juices and cereals). Getting enough D is especially an issue for vegetarians or vegans or others who don't eat fish or drink milk.

In fact, on average, adults consume only about 60% of the FDA daily value of vitamin D from food sources -- and even with supplements many people still come up short, because these don't always provide 100% of the daily value. Obese people are often low on vitamin D, even if they meet the daily value, because the fat-soluble vitamin can be taken out of blood circulation and deposited in body fat.

We may be even shorter of vitamin D than we knew. In a 2006 review of the vitamin D literature published in the American Journal of Clinical Nutrition, researchers at the Harvard School of Public Health concluded that the recommended daily intake may need to be more than doubled to reduce the risk of chronic disease.

That's because, aside from keeping bones and teeth healthy and strong, vitamin D is increasingly thought to play a role in reducing the risk of colon, breast and prostate cancers; stroke; hypertension; congestive heart failure and diabetes. It would take about 4 ounces of fish, 4 cups of milk or up to 10 servings of fortified cereal to meet the current daily recommendation of 400 IU of vitamin D.

But just five "optimized" mushrooms would more than meet this recommended amount. When these do come to market, they'll be a delicious way to boost your vitamin D -- especially if you eat them outdoors.

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Susan Bowerman is a registered dietitian and assistant director of the UCLA Center for Human Nutrition.

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Lots of nutrition in a little fungus

Mushrooms are the only natural fruit or vegetable source of vitamin D. They've got a lot of other things going for them too. They're a good source of copper, potassium, selenium and the B-vitamins niacin, pantothenic acid and riboflavin . They also contain ergothioneine, a potent antioxidant, in amounts greater than those found in chicken liver and wheat germ, the other two richest sources. They're fat-free, cholesterol-free and very low in calories.

-- Susan Bowerman