Tea, coffee, chocolate, avocados, and fatty fish all have good-for-you qualities.

O K, so we know that spinach and carrots are good for us, but tea, coffee, chocolate, avocados, and fatty fish also having disease-preventing and health-enhancing properties?

Yes. Some of these superfoods contain antioxidants, which fight the damage from disease-causing "free radicals" (unstable molecules that damage cells). Others have omega-3 fatty acids, which promote heart health and may even help to cheer you up when you're feeling down.  Here's a rundown on how these five foods can benefit your health.

Tea

Topping the list of surprising superfoods is tea -- any type that comes from the leaves of the plant Camellia sinensis, including black, green, white, and oolong.

Many studies have looked at the health benefits of tea. While the jury is still out on some of these potential benefits, there appears to be compelling evidence for tea's ability to reduce the risk of heart disease.

There are some intriguing studies that tea may prevent cancer, reduce the risk of Alzheimer's disease, and impact bad breath, and while these studies are more speculative, the strongest evidence is on the reduction of coronary heart disease risk.

Tea's secret ingredient is catechins, a type of flavonoid from the family of disease-fighting antioxidant phytochemicals that is also found in fruits, vegetables, and red wine.

Not just any cup of tea will provide you with a healthy dose of flavonoids. Strong, steeped tea is richest in these phytochemicals. And the longer you steep your tea, the more of these healthy extracts your drink will contain.

Because iced tea is typically diluted, it's not as good a source as hot tea. Bottled teas start off with low levels of flavonoids, and tend to lose potency over time. Decaffeinated tea is a good option, though it has about 10% fewer phytochemicals than tea with caffeine.

So how much tea should you drink? Some studies have suggested that drinking three cups each day can reduce your risk of heart disease.

Choose tea whenever you can, it can contribute as much antioxidants as a serving of fruit or vegetable without the calories.

If you add sugar to your tea, do so sparingly. This  addition can turn a naturally non-caloric tea into a high-calorie drink.

Dark Chocolate

Good news for chocolate lovers: dark chocolate (as opposed to milk chocolate or white chocolate) contains healthful flavonoids similar to those found in tea, red wine, fruits, and vegetables.

Studies have shown that small portions of dark chocolate can improve blood vessel flow, especially in older adults, and may improve blood sugar and insulin sensitivity to help reduce the risk of diabetes.

One study, published in the journal Hypertension, reported that the antioxidants found in dark chocolate could help reduce high blood pressure. Study participants who ate chocolate also reduced their LDL "bad" cholesterol levels, and improved insulin sensitivity. A little chocolate goes a long way, however. The study subjects were limited to a small portion of dark chocolate per day and cut calories elsewhere in their diets to avoid weight gain.

In another study, reported in The Journal of the American Medical Association, researchers found that the flavonoids in dark chocolate helped prevent stiffening of blood vessels in adults over 50. And a study published in the American Journal of Clinical Nutrition found that dark chocolate may help prevent diabetes by improving insulin sensitivity in healthy adults.

The dark chocolate used in these studies has high levels of flavonoids and somewhat of a bittersweet taste -- different from the creamy milk chocolate many enjoy. The flavonoids come from extracts of the cocoa bean. By choosing dark chocolate with a high percentage (70%) of cocoa, you'll get more of these health-enhancing antioxidants. Most dry cocoa mixes don't contain these health-promoting substances.

Of course, all chocolates -- including dark chocolate -- have both positive and negative attributes. Chocolate candy has plenty of saturated fat and sugar, which can lead to weight gain. A standard-size bar of Hershey's Dark Chocolate has 531 calories.

Still, at the very least, chocolate is a satisfying treat that can be an alternative to sugary snacks that provide calories with little nutritional value, says the American Dietetic Association.

So enjoy small portions of dark chocolate as part of a healthy diet (and make up for the calories with physical activity).

Fatty Fish

It's hard to imagine that any food called "fatty" could be good for you, but when it comes to food from the sea, the fattier the fish, the better. Coldwater fatty fish, such as salmon, trout, herring, tuna, sardines, and mackerel, are rich in omega-3 fatty acids, a type of unsaturated fat that promotes health in many ways. The real strength of omega-3s appears to be their ability to lower blood cholesterol, preventing blood clots and heart attacks.

Many studies have supported the idea that omega-3 fatty acids can lower cholesterol and triglycerides (blood fats), and reduce the inflammation associated with a risk of heart disease. The science for this effect is so compelling that the American Heart Association recommends eating two servings of fatty fish weekly.

Emerging evidence suggests that omega-3s may also affect mood. A study from the University of Pittsburgh found that low levels of omega-3s were associated with mild to moderate symptoms of depression and moodiness, while people with higher levels were found to be more content.

Eating fish such as salmon and trout is the easiest and best way to get a healthy dose of omega-3 fatty acids. If you don't enjoy them, you can also get it in plant foods such as flaxseed, walnuts, oils, but these sources are not as good as fatty fish."

But keep in mind that you can undo the health benefits of fish if you eat it fried.

Fried foods add lots of extra calories, and saturated fat that is not good for your waistline or your heart. So fire up the grill or put your fish under the broiler for a quick, tasty, and heart-healthy meal. Keep portions to 4 ounces. While the fat in the fish is good for you, it adds to the calorie count.

Avocados

Yes, these luscious green fruits are full of fat. But most of it is the heart-healthy, monounsaturated kind that can help lower both total cholesterol and "bad" cholesterol.

Avocados contain health-promoting carotenoids. They're also rich in vitamin E and potassium, and contain some fiber to help fill you up.

Avocados are rich in beta-sitosterol, a natural substance that has been shown to reduce cholesterol levels. The avocado also contains plant chemicals and antioxidants, all of which contribute to good health.

While avocados are a great way to add flavor and texture to meals without too much saturated fat, portion control is critical.

Slice avocados into salads; float slices or cubes of avocado on top of soups, or use avocado instead of butter, cream cheese, or mayonnaise on breads, bagels, and sandwiches.

Coffee

Your morning cup of coffee not only helps wake you up, it may have health benefits. The caffeine in coffee stimulates the brain and nervous system, and may lower your risk of diabetes, Parkinson's disease, mood problems, headaches, and even cavities.

Coffee contains many beneficial substances including chlorogenic acid, a compound in the antioxidant family that may improve glucose (sugar) metabolism. Another perk is that coffee contains magnesium, a mineral that can also improve insulin sensitivity and enhance glucose tolerance.

A review of 15 studies on coffee and type 2 diabetes published in The Journal of the American Medical Association found that people who regularly drank coffee had lower risk of type 2 diabetes. Most people in the studies drank coffee prepared with the drip method.

So enjoy your coffee in moderation, and keep in mind that a healthy diet, normal body weight, and regular exercise are your best defense against developing type 2 diabetes.

Another plus is that coffee is naturally calorie-free. But if you load it up with cream, sugar, whipped cream, and/or flavored syrup, the extra fat and calories can nullify any potential benefits.

Of course, it takes more than five foods to make a healthy diet.

The real key to preventing disease and promoting health is a lifestyle of regular physical activity, healthy eating patterns that include a variety of nutritious foods and ways to manage stress that work for you.