Q. What's the healthiest dark chocolate in terms of percentage of cocoa? -- Gayle, San Diego, CA

A. Shoot for 70% and higher. The percentage refers to the amount of cocoa solids in the product. The more cocoa, the more flavonoids, polyphenol compounds also found in apples, green tea, and red wine (though one study found that chocolate beats them in health power, hands down). Chocolate's flavonoids can block changes to cholesterol that makes it more likely to stick to your arteries, and the compounds may help protect your DNA from the damage that can cause cancer. It's also likely that they improve the health of your blood vessels, increase blood flow, and make you smarter. It even helps put rats in a good mood, and fruit flies live longer, though those studies may or may not be applicable to humans (we think the mood one does work, if you test our brides). Notice that we said the more cocoa, the more flavonoids, not the more chocolate you eat, the more flavonoids you get . . . stick to an ounce or so a day to avoid dark chocolate's dark side: calories.

Q. I read that peanut butter and peanuts can lower cholesterol. My son, who is 11, was recently tested and has high cholesterol (242). I've been buying reduced-fat peanut butter. Is this a better choice for lowering cholesterol than regular peanut butter? -- Linda, Babylon, NY

A. It's smart to switch to low-fat cheese and avoid meats, but stick with regular peanut butter. It's not often we get to say that all the healthy stuff is in the fat. But peanut and other nut butters (as well as nuts that are unsalted and roasted in their own oils) contain polyunsaturated and monounsaturated fats, which can help lower lousy cholesterol (LDL) without lowering healthy cholesterol (HDL). A Harvard study also found that having as little as 5 tablespoons of peanut butter every week also lowers type 2 diabetes risk by 20%. Contrary to rumor, real (made from peanuts alone) peanut butter isn't full of dangerous trans fats, either.

Don't forget peanuts in their original format (they're actually legumes, but don't tell your children). Nuts are the perfect kid snack, particularly for Generation XL (and their pudge-prone parents). Popping a handful a few times a week can prevent both you and your child from getting too chunky. In one study of more than 80,000 women, those who ate nuts two or more times a week were less likely to pack on the pounds over the years, even though nuts are fairly high in calories (165 calories in an ounce of dry-roasted peanuts). One caveat about peanut butter: While the fat is healthy, the sugar isn't. Solve that dilemma by choosing no-sugar varieties, and make your PB&J with low-sugar fruit spreads.

Q. Why does nonfat yogurt have so many grams of sugar? -- Anonymous

A. In a word: taste. We're programmed to love the taste of fat. It's an evolutionary thing: Eons ago, before the invention of the supermarket, we had to grab all the calories we could when they presented themselves, in case famine was around the corner. Fat has lots of calories -- it weighs in at 9 calories per gram versus 4 calories per gram in carbs. We even have taste buds for it. And when fat's missing from our food, we need something satisfying to replace it. Food manufacturers know that we are not going to plunk down $1.29 for something that tastes like spackling paste, so they generally up the addictive sugar as they suck out the fat. Yes, we said addictive -- your brain gets addicted to it. Fortunately, manufacturers have also figured out that many people don't want all that sugar, either, so they've created good-tasting, low-fat, low-sugar plain yogurts. Greek yogurt is generally the creamiest, although there are other low and nonfat yogurts without added sugar (just read labels: many contain artificial sweeteners). Stir fresh fruit into it (then you get some nice complementary texture in there, too), or add sugar-free chocolate syrup.