Making the Case for Eating Fruit
Experts agree that we are eating too much sugar, which is contributing to obesity and other health problems. But in the rush to avoid sugar, many low-carb dieters and others are avoiding fruits. But fresh fruit should not become a casualty in the sugar wars, many nutrition experts say.
Dr. David Ludwig, the director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital, said that sugar consumed in fruit is not linked to any adverse health effects, no matter how much you eat. In a recent perspective piece in The Journal of the American Medical Association, he cited observational studies that showed that increased fruit consumption is tied to lower body weight and a lower risk of obesity-associated diseases.
Whole fruits, he explained, contain a bounty of antioxidants and healthful nutrients, and their cellular scaffolding, made of fiber, makes us feel full and provides other metabolic benefits. When you bite into an apple, for example, the fruit's fiber helps slow your absorption of fructose, the main sugar in most fruits. But fiber is not the full story.
"You can't just take an 8-ounce glass of cola and add a serving of Metamucil and create a health food," Dr. Ludwig said. "Even though the fructose-to-fiber ratio might be the same as an apple, the biological effects would be much different."
Fiber provides "its greatest benefit when the cell walls that contain it remain intact," he said. Sugars are effectively sequestered in the fruit's cells, he explained, and it takes time for the digestive tract to break down those cells. The sugars therefore enter the bloodstream slowly, giving the liver more time to metabolize them. Four apples may contain the same amount of sugar as 24 ounces of soda, but the slow rate of absorption minimizes any surge in blood sugar. Repeated surges in blood sugar make the pancreas work harder and can contribute to insulin resistance, thereby increasing the risk for Type 2 diabetes.
"If we take a nutrient-centric approach, just looking at sugar grams on the label, none of this is evident," Dr. Ludwig said. "So it really requires a whole foods view."
Fruit can also help keep us from overeating, Dr. Ludwig said, by making us feel fuller. Unlike processed foods, which are usually digested in the first few feet of our intestines, fiber-rich fruit breaks down more slowly so it travels far longer through the digestive tract, triggering the satiety hormones that tend to cluster further down the small intestines.
Another nutrition expert, Dr. Robert Lustig, a professor of pediatrics at the University of California, San Francisco, who has called sugar "toxic" at high doses and fructose the most "actionable" problem in our diet, is still a fan of fruit. "As far as I'm concerned, fiber is the reason to eat fruit," since it promotes satiety and the slow release of sugar. He adds a third benefit from fiber: it changes our "intestinal flora," or microbiome, by helping different species of healthy bacteria thrive.
Neither doctor favors certain fruits over others. But Dr. David L. Katz, director of the Yale University Prevention Research Center, said that "to maximize the benefit, you actually want a variety" of fruits. He advises "eating the rainbow," since different colors signal different types of antioxidants and nutrients.
All three experts caution against choosing juice over whole fruit. While the best juice has nothing added, nothing subtracted, some important changes take place when you turn fruit into liquid. Chewing the whole fruit slows down consumption, Dr. Katz said, compared to when you "take an 8-ounce juice and just pour it down the hatch," which not only makes it easier to ingest more calories, but releases fructose faster into the bloodstream.
Plus, he said, with juicing, "you reduce some of the metabolic benefit of the fiber by pulverizing it so fine; it changes the physical structure." Commercially produced juices are particularly concerning since they are often filtered, removing fiber altogether. If you opt for juice, tossing whole fruit in a blender rather than squeezing it offers the best chance of retaining most of the fiber, vitamins and minerals.
Dried fruits also hold one of the main disadvantages of juices: volume. Dried fruit essentially concentrates the calories and sugar into smaller packets, making it easier to consume excess calories. But dried fruit is better than juice, Dr. Katz said, because it preserves the fruit's cellular structure, along with the health assets that provides. And since dried fruit travels easily and does not rot, it can make the difference in eating any fruit at all.
Dr. Katz's hierarchy? Fresh fruit, followed closely by dried fruit, with sweetened dried fruit a distant third, and juice in fourth place.
He said we should remember "a law we all learned from Aesop" and judge fructose "by the company it keeps," fiber and all.