1. Spinach

For $1.50, the price of a large bag of spinach at most grocery stores, you can reduce your risk of developing osteoporosis, lower your cholesterol, and raise your I.Q. Spinach is an excellent bone-builder, containing vitamin K, calcium, and magnesium. It's also high in flavonoids, plant molecules that act as antioxidants, which have been shown to prevent breast, stomach, skin, and ovarian cancer. Spinach is a great source of vitamin A and vitamin C, which not only keep you from getting sick in the winter, but also de-clog your arteries and reduce heart disease.

Spinach contains antioxidants that neutralize free radicals in the brain, thereby preventing the effects of aging on mental activity. Scientific studies have demonstrated that both animals and people who eat a few servings of spinach per day improve their learning capacities and motor skills.

Serving ideas: Sauté spinach with olive oil, pine nuts, and raisins — the olive oil will help you to better absorb its nutrients. Don't love the flavor so much? Try these spinach brownies from Jessica Seinfeld's Deceptively Delicious cookbook — you won't taste a thing.

2. Eggs

In the Snackwell-crazed '90s, dieters feared eggs because of their fat and cholesterol content and suffered through millions of tasteless egg-white omelets. But research has shown little, if any, connection between dietary cholesterol and blood cholesterol, and the humble egg is finally being recognized for the remarkably complete set of nutrients it provides. It makes sense: Something that contains the ingredients for an entire life can give you the fuel you need to get through the morning.

Eggs are a great source of protein, containing all eight amino acids (if you eat the whole thing). As any healthy dieter knows, protein is essential for staying full and having energy.

Serving ideas: For breakfast on the go, roll up a veggie omelet in a whole-wheat wrap. Or, update the classic egg salad by chopping yours up with Italian tuna, black olives, and some olive oil and vinegar.

3. Blueberries

A Tufts University study found blueberries were the number one source of antioxidants among 60 fruits and vegetables analyzed. Blueberries contain antioxidants that can (get ready): prevent ulcers, cataracts, and glaucoma; decrease risks of heart disease and various types of cancer; and lower cholesterol. They can also reduce aging of the brain, keeping your memory sharp and diminishing the effects of dementia and Alzheimer's disease.

Serving ideas: Throw some frozen ones in the blender with honey or agave syrup for a granita-like treat. Or, serve in a salad with spinach, sliced almonds, and balsamic vinaigrette for a light and gourmet lunch.

4. Apples

Eating an apple a day can keep all kinds of doctors away, from physicians to dentists. Apples contain both insoluble and soluble fiber, which not only make them filling, but also work double time to reduce cholesterol. Some doctors even recommend drinking apple juice after eating a fatty meal to reduce the food's negative effects on your body.

Apples have been proven to reduce the risk of heart disease. And if that's not enough to make you bite into a Fuji or McIntosh, consider this: Chewing apples stimulates saliva, which scrubs stains off your teeth and freshens breath instantly.

Serving ideas: Spread peanut butter on sliced apples for a yummy taste of childhood. Or, dice them up in your oatmeal before cooking and sprinkle with cinnamon for an apple pie-flavored breakfast.

5. Winter Squash

One cup of winter squash provides 170 percent of your daily requirement of vitamin A, a nutrient necessary for night vision that's hard to find in other foods. Squash's bright orange color comes from a high dose of carotenoids, antioxidants that prevent eye degeneration due to aging and filter out carcinogenic light rays. Makes you think of jack-o'-lanterns in a new "light," doesn't it?

Roast the seeds alongside the flesh and you'll reap a host of other benefits. Winter squash seeds contain a significant amount of L-tryptophan, which can help to prevent depression. They're also a rich source of magnesium, a mineral Americans don't consume nearly enough that's vital to almost every bodily function. Eating your daily dose of magnesium will lower your risks for heart disease, abdominal obesity, and diabetes.

Serving ideas: Mix canned or pureed squash with cinnamon and the sweetener of your choice for a decadent and surprisingly low-cal treat reminiscent of Thanksgiving candied yams. One-half cup of pureed pumpkin has 40 calories, in contrast with yam's 180 (and that's if you don't add butter or marshmallows). Or, roll the seeds in cinnamon and sugar, crunchy sea salt, or curry powder, then roast them in the oven. And don't limit yourself to pumpkin — delicata and kabocha squash seeds are equally nutritious, with their own unique, nutty flavors.

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