As it turns out, your grandmother was right. An apple a day really might keep the doctor away.
Indeed, it shouldn't come as any surprise -- dozens of studies have shown us that fruits and vegetables are the cornerstones of a healthy diet.
However, the same may not hold true when it comes to your morning apple juice. Or orange juice, for that matter.
Americans often turn to juice as a healthy alternative to soda and other sweetened drinks. In fact, the average American drinks approximately 11 gallons, or 177 cups of juice a year, according to the World Development Indicators Database.
But new data suggests that for women at least, juice consumption may contribute to an increased risk of diabetes.
The study, recently published in the journal Diabetes Care, looked at data from the Nurses' Health Study, which has followed the health and lifestyles of more than 70,000 women over an 18-year period.
The authors found an association between fruit and fruit juice intake and the likelihood of developing type 2, or "adult onset" diabetes.
Those women who consumed an average of one or more servings of fruit juice a day were 18 percent more likely to develop type 2 diabetes, whereas those who consumed three or more servings of whole fruits or one serving of green leafy vegetables had significantly lower rates of the disease.
Putting the Squeeze on Juice
Back in 1916, advertisers coined the slogan "Drink an Orange." According to the author of "Citrus: A History," this marketing campaign was responsible for the appearance of orange juice next to our ham and eggs.
Today, that glass of OJ is a morning ritual for many Americans. Should we be changing our ways?
Experts are split on the issue; while some suggest avoiding juice completely, others say that moderation is key, setting a limit of four to six ounces a day.
But this half-cup serving is much less than the typical 16 to 20 ounces many people consume daily, according to Connie Diekman, director of nutrition at Washington University in St. Louis.
To make matters more confusing, according to the USDA's MyPyramid, "Any fruit or 100 percent fruit juice counts as part of the fruit group. Fruits may be fresh, canned, frozen or dried, and may be whole, cut up or pureed."
Experts worry such guidelines could steer consumers away from fruit -- even at a time when most Americans don't get nearly enough fruit as it is.
"We're so lacking in terms of eating any fruit," says Keith Ayoob, associate professor of pediatrics at the Albert Einstein College of Medicine. "I'd encourage people to get their fruit intake from more than juice alone.
"Besides, there are more varieties of fresh fruit than fruit juice," he continues. "Think about it -- ever see 100 percent kiwi juice for sale? It would be a shame not to take advantage of it, for the sake of health, but also for our own enjoyment."
But why the difference? In essence, juicers strip the valuable fiber from fruit. Fiber plays an important role in slowing the absorption of sugar, thus blunting the accompanying insulin spike.
It is for these reasons that Carla Wolper, a clinical nutritionist at the Center for Women's Health at Columbia University Medical Center, recommends that her patients stay away from juices.
"An eight-ounce glass of OJ is 110 calories. A six-ounce orange is 60 calories, takes longer to consume than liquid juice, and stays in the stomach longer due to its nonliquid content," she explains. "People are more satisfied eating an orange than drinking juice."
Dr. Ken Fujioka, director of nutrition and metabolic research at the Scripps Clinic Center for Weight Management, has performed head-to-head studies of juice and whole fruit, finding that whole fruit is much better for blood sugar control and weight. He recommends that his patients "eat an orange or banana rather than their morning juice."
A True Link?
Still, the issue may be more complex than those decisions we make in the beverage aisle. In fact, juice may be taking the rap for other unhealthy habits.
So, while it may be true that those people who drink more juice are more likely to develop diabetes, it cannot yet be concluded that juice causes diabetes.
"We may be looking at a marker of eating behavior or lifestyle overall, not just the difference between fresh fruit and fruit juice," says Ayoob. "It may be that people who take the trouble to eat whole fruit are less likely to go for the most convenient foods in general and are willing to take the extra time to stock whole fruit in the home and make time to peel and eat it."
According to Dr. Francine Kaufman, an authority on diabetes and obesity and past president of the American Diabetes Association, "Fruit consumption often tracks with a very high-quality diet."
Dr. William Yancy at the Center for Health Services Research in Primary Care agrees. "I would hypothesize that people who consume large amounts of juice have an overall less healthy diet and other behaviors compared with people who consume large amounts of fruits and vegetables," he says.
Additionally, even in light of the average American's 11-gallon-per-year juice consumption, we slurp down almost five times as much soda.
"The bit we often overlook when asking questions about what people are eating is: instead of what?" says Dr. David Katz, co-founder of the Yale Prevention Research Center. "If you are drinking juice instead of soda, you are trading up and it's a good thing. But if you are drinking juice instead of water, it is likely contributing to the common daily excess of sugar and calories, and could be improved."
If there is any silver lining, it may be that Americans are making slow progress in increasing fruit and vegetable intake. And because we're still not eating enough fruit, anything that provides essential vitamins and nutrients is preferable to the less nutritious alternatives, to some degree.
"We benefit both from the good stuff we choose to eat and the less good stuff we choose not to," says Katz. "Fruit is best, then fruit juice, then sugar-sweetened beverages, which offer the liabilities of juice without the advantages."