Time to go nuts, calorie counters
By Richard A. Marini San Antonio Express-News When it comes to being "part of a balanced diet," nuts have undergone quite the rehabilitation. Time was, anyone worried about gaining weight would steer well clear of walnuts, almonds, cashews, pistachios, peanuts (although technically a legume) and other nuts because they were considered "fattening" -- that is, high in fat and calories. And their "bet you can't eat just one" tastiness makes it easy to overindulge. Just a couple becomes a handful, becomes handfuls and then -- poof! -- the whole bag is gone.
Today we understand that nuts contain plenty of good stuff, including heart-healthy unsaturated fats, vitamins, minerals and plenty of fiber. Studies suggest that eating nuts (within reason) can help you stay thin and may cut the risk of some major causes of death, including heart disease and cancer -- although nut eaters also tend to lead a healthier lifestyle, so nuts shouldn't get all the credit.
In other words, nuts are now firmly on the "Eat This" side of the "Eat This, Not That" equation. Except, of course, for that pesky calorie thing. Nuts are what those in the nutrition business call "energy dense," meaning they contain more bang for the caloric buck than most foods.
Or do they? A recent study in the American Journal of Clinical Nutrition found that almonds, at least, do not contain as many calories -- or at least as many "available" calories -- as previously thought. For decades, food companies have relied on a simple mathematical formula to figure out how many calories their products contain: Multiply four calories per gram of both protein and carbohydrates, plus 9 calories per gram of fat, divide by the number of servings and voila, they're ready to fill out the Nutrition Facts label. When it comes to almonds and perhaps other nuts, the math may not add up, according to Janet A. Novotny, from the USDA's Agricultural Research Service in Beltsville, Md., and lead author of the almond study. And that may be good news for anyone trying to lose -- or at least not gain -- weight.
In Novotny's study, 18 healthy adults ate almonds as part of a carefully controlled diet. One serving of whole almonds contains 161 calories, according to the Nutrition Facts label, but when they compared their subjects' caloric intake to their caloric outflow (don't ask) they discovered only about 129 calories per serving had actually been absorbed -- almost 20 percent less than you'd expect. So why don't we absorb all the calories the humble almond has to offer?
Blame it on the hardness of the cell walls. "That's what makes almonds so difficult to chew," explained Novotny. You may think you're swallowing small pieces of chewed-up almonds, but to your digestive tract they're veritable boulders. And as these pieces pass through your body, they're only partially digested and absorbed into your system. The other 20 percent? Flushed away.
Bottom line, according to Novotny, "Almonds aren't as digestible as most other foods." And it's not just almonds. Novotny has found the same thing with pistachio nuts, albeit to a lesser extent. "Pistachios are softer, so only about 5 percent of the calories go unabsorbed," she said, adding that she's also exploring the absorbability of calories in other nuts, including walnuts, and even peanut butter.
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