You can’t go wrong with fruit, which is naturally gluten-free. In good news for anyone who has to eat gluten free, fruits (and vegetables) lower your risk of heart disease and stroke. This news comes from studies that look at the eating habits of large groups of people and the diseases they get.
It’s a little trickier when you try to match individual fruits to specific diseases. But researchers are trying..with mixed success. Here’s some of what they’ve learned.
“Twenty or thirty years ago, people evaluated a fruit or vegetable by how much vitamin C it contained,” says Rui Hai Liu, a fruit researcher at Cornell University in Ithaca, New York.
Clearly, vitamins and minerals matter. Potassium, for example, may account for the lower risk of stroke in people who eat more fruits and vegetables because it lowers blood pressure.
But there are more than 8,000 bioactive compounds in fruits and vegetables, including the group known as polyphenols, notes Liu. And they may one day also help explain why eating those foods is good for you.
Whether or not you follow a diet that is gluten free, fruit can be a healthy snack. Fruit, howeber, should be eaten as whole fruit, only occasionally, if at all, as a juice.
Here are examples where cranberry juice and tart cherry juice can be beneficial under certain circumstances and where the evidence for pomegranate juice, blueberry, and grape juice isn’t solid enough to justify drinking it every day.
“During the early stages of a urinary tract infection, when you first feel an urgency to urinate and then a burning sensation, what’s happening is that little hairs on E. coli bacteria, called fimbriae, are starting to stick to the inside of your bladder wall,” says Amy Howell of Rutgers University in Chatsworth, New Jersey.
“However, these fimbriae don’t bind all at one time,” she explains.
“One hair will stick, then another, and then another until suddenly all of them are cemented to the bladder cells, and it’s too late to get them off.”
If you can dislodge the fimbriae before they’re all attached, says Howell, there’s a chance of preventing an infection.
That’s where cranberries come in. They contain polyphenols called proanthocyanidins (PACs), which prevent fimbriae from adhering to the bladder cells.
Tart cherries, also known as sour or Montmorency cherries, are used to make jam, preserves, and pies. Sweet cherries, like the Bing and Rainier varieties, are grown primarily for fresh eating. While both contain polyphenols, tart cherries have more.
Most of the half-dozen studies in humans have looked at whether tart cherry juice can relieve muscle pain and reduce the signs of inflammation after exercise.
In the most dramatic one, 51 men and women participated in a 200-mile relay race from Mt. Hood in Oregon to the Pacific Coast. Each runner averaged about 16 miles over the hilly course that crossed two mountain ranges.
For seven days before and on the day of the race, half of the runners drank 20 ounces of tart cherry juice mixed with apple juice, while the other half drank Kool-Aid fruit punch that matched the sugar concentration of the juice.
At the conclusion of the race, the cherry-apple juice drinkers reported significantly less muscle pain than the fruit punch drinkers.
Rising PSA scores slowed down in 46 men who had been treated for prostate cancer with surgery or radiation when they drank 6 to 8 ounces of pomegranate juice every day for up to 33 months. (A rising PSA, or prostate-specific antigen, score may indicate a growing prostate cancer.)
And when blood from the men was mixed with prostate cancer cells in test tubes, it slowed down the proliferation—and sped up the death—of the cells.
But there was no control group, so there was no way to tell whether the men’s PSA levels would have risen at the same pace without pomegranate juice. The results of a followup study, which did have a control group, have not been released.
Robert Krikorian of the University of Cincinnati and his colleagues have conducted two very small preliminary studies in older adults with mild cognitive impairment, which is memory decline beyond what normally occurs with age but not severe enough to interfere with daily life.
In the first study, five men and women who drank roughly two cups of grape juice every day for three months were able to remember 39 words that were read to them, while seven similar adults who drank a juiceless placebo beverage remembered 33 words. The juice drinkers did no better on a test that required them to recall patterns they had been shown, though.
In the more recent study, five men and four women who drank roughly two cups of blueberry juice every day for three months were better able to remember pairs of unrelated words than people in another study who drank a juiceless beverage. The juice drinkers were no better at recalling single words, however.
Even the researchers stressed that the results were preliminary. “Replication of the findings in a larger controlled trial will be important to corroborate and amplify these data,” they wrote.
We do know berries help improve the memories of laboratory rats, but it’s too early to know whether berries or grape or berry juice does the same in people.
If you are eating gluten free, fruits are probably on your go-to snack list. What is your favorite fruit?
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