Why it's healthy: Guava has a higher concentration of lycopene -- an antioxidant that fights prostate cancer -- than any other plant food, including tomatoes and watermelon. In addition, 1 cup of the stuff provides 688 milligrams (mg) of potassium, which is 63 percent more than you'll find in a medium banana. And guava may be the ultimate high-fiber food: There's almost 9 grams (g) of fiber in every cup.
How to eat it: Down the entire fruit, from the rind to the seeds. It's all edible -- and nutritious. The rind alone has more vitamin C than you'd find in the flesh of an orange. You can score guava in the produce section of higher-end supermarkets or in Latin grocery stores.
Hidden in the leafy-greens cooler of your market, you'll find this slightly bitter, salty vegetable, which is actually native to the Mediterranean.
Why it's healthy: A half cup of cooked Swiss chard provides a huge amount of both lutein and zeaxanthin, supplying 10 mg each. These plant chemicals, known as carotenoids, protect your retinas from the damage of aging, according to Harvard researchers. That's because both nutrients, which are actually pigments, appear to accumulate in your retinas, where they absorb the type of shortwave light rays that can damage your eyes. So the more lutein and zeaxanthin you eat, the better your internal eye protection will be.
How to eat it: Chard goes great with grilled steaks and chicken, and it also works well as a bed for pan-seared fish. Wash and dry a bunch of Swiss chard, and then chop the leaves and stems into 1-inch pieces. Heat a tablespoon of olive oil in a large sauté pan or wok, and add two garlic cloves that you've peeled and lightly crushed. When the oil smokes lightly, add the chard. Sauté for 5 to 7 minutes, until the leaves wilt and the stems are tender. Remove the garlic cloves and season the chard with salt and pepper.
This old-world spice usually reaches most men's stomachs only when it's mixed with sugar and stuck to a roll.
Why it's healthy: Cinnamon helps control your blood sugar, which influences your risk of heart disease. In fact, USDA researchers found that people with type-2 diabetes who consumed 1 g of cinnamon a day for 6 weeks (about 1/4 teaspoon each day) significantly reduced not only their blood sugar but also their triglycerides and LDL (bad) cholesterol. Credit the spice's active ingredients, methylhydroxychalcone polymers, which increase your cells' ability to metabolize sugar by up to 20 times.
How to eat it: You don't need the fancy oils and extracts sold at vitamin stores; just sprinkle the stuff that's in your spice rack (or in the shaker at Starbucks) into your coffee or on your oatmeal.
Although the FDA classifies purslane as a broad-leaved weed, it's a popular vegetable and herb in many other countries, including China, Mexico, and Greece.
Why it's healthy: Purslane has the highest amount of heart-healthy omega-3 fats of any edible plant, according to researchers at the University of Texas at San Antonio. The scientists also report that this herb has 10 to 20 times more melatonin -- an antioxidant that may inhibit cancer growth -- than any other fruit or vegetable tested.