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The past year has been a good one for chocolate makers and chocolate lovers. Findings from recent studies suggest that eating chocolate can help prevent heart disease, ward off diabetes and may even reduce the risk of stroke and dementia by improving blood flow to the brain.

The latest study, published last week by the American Heart Association, found a daily dose of chocolate lowered blood pressure, reduced LDL (bad) cholesterol and improved how the body used insulin (the hormone that clears sugar from the bloodstream) in 20 men and women with high blood pressure. (The researchers noted, however, that chocolate should not replace blood-pressure medication and exercise.)

But before you indulge in a couple of Hershey bars or a box of Godiva chocolates, you'd better read the label: Not all chocolate is created equal.

Whether you'll reap its health benefits depends on the type of chocolate you eat and, of course, the quality of your overall diet.

The studies that link eating chocolate with improved vascular health and a lower risk of heart disease gave volunteers dark chocolate -- not milk chocolate or white chocolate.

In the most recent study, participants who ate 100 grams of dark chocolate for 15 days saw their blood pressure and cholesterol numbers drop. The volunteers who ate 90 grams of white chocolate did not experience a change in blood pressure or cholesterol readings.

The difference between dark and milk chocolate has to do with the ratio of milk to chocolate liquor -- the name given to the cocoa mass used to produce the chocolate. Dark chocolate has the most chocolate liquor, and thus the most flavonoids, the natural compounds in cocoa beans that give some chocolate a bittersweet taste.

Milk chocolate contains fewer flavonoids because it's diluted with milk (it also tends to have more sugar). White chocolate contains no chocolate liquor, so it has no flavonoids (It's usually a mix of sugar, cocoa butter, milk solids, lecithin and vanilla).

Flavonoids have been shown to inhibit blood-clot formation, help blood vessels relax and slow the oxidation of LDL cholesterol.

In another recent study, researchers from the University of California at San Francisco gave 21 healthy adults one or two chocolate bars every day for two weeks: a dark chocolate bar with a high-flavonoid content or a dark chocolate bar with the flavonoids removed. Only those who ate the flavonoid-rich chocolate showed improvement in blood-vessel function. It's thought that flavonoids trigger the release of substances that increase blood flow in arteries.

Dark chocolate isn't the only food that contains flavonoids.

Flavonoid is the umbrella term given to some 4,000 compounds that impart the colourful pigments to fruits, vegetables and herbs. They're also found in legumes, nuts and grains.

While thousands of flavonoids exist, only a few have been widely studied. Some notable flavonoids include genistein in soybeans and other legumes, quercetin in apples and onions, polyphenols in berries and red wine, and catechins in black and green tea and dark chocolate.

Flavonoids protect plants by repairing damage and shielding them from environmental toxins. It seems that when we eat these plants, we benefit as well. Researchers from Finland found that, among 10,000 men and women, those with the highest flavonoid intake had a 46 per cent lower risk of developing lung cancer. This study, as well as two others, also linked a higher flavonoid intake with a lower risk of dying from heart disease.

While soybeans, apples, onions, blueberries, red wine and tea all contain flavonoids, dark chocolate appears to contain more than any other food. In fact, dark chocolate contains about five times as much antioxidant activity as blueberries.

Just because dark chocolate may have some health benefits doesn't mean you can scoff back as much as you want. One hundred grams of dark chocolate delivers roughly 470 calories -- straight to your waistline, if you're not careful. If you're going to eat more dark chocolate, you're going to have to exercise more or cut back elsewhere to prevent weight gain.

A 100-gram dark chocolate bar also packs in 30 grams of fat from cocoa butter.

If you're planning to add dark chocolate to your diet, be choosy. Read labels to look for bars that contain at least 70 per cent cocoa solids (cocoa mass). Milk chocolate tends to have 30 per cent to 40 per cent cocoa solids, but brands vary.

Stay clear of dark chocolate mixed with caramel, marshmallows, honey and rice crisps, ingredients that add extra sugar, fat and calories and dilute the flavonoid content. Dark chocolate bars mixed with flavours, such as raspberry or orange, also tend to have a lower percentage of cocoa solids.

Lastly, don't forget about those other flavonoid-rich foods. Unlike chocolate, fruits and vegetables come with additional nutrients and fewer calories.

And let's face it -- a few squares of the finest chocolate won't make up for a diet that's high in fat and sodium and low on produce. But it's nice to know that you don't need to feel guilty when you do enjoy a piece of dark chocolate.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Visit her website, lesliebeck.com.

Chocolate's dark truth

If you're going to indulge, choose dark chocolate over milk to boost your flavonoid intake.

Look for bars that contain at least 70 per cent cocoa solids. Here's how some brands compare: