Fruit with benefits: a tart cherry a day ...
It's a little trickier when you try to match individual fruits to specific diseases. But researchers are trying .. with mixed success. Hero'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 Hal 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.
At least that's what fruit researchers are banking on. Just keep in mind that many studies haven't been confirmed by other researchers, and that early studies often don't pan out for a variety of reasons:
* The studies are usually small, so the results are less reliable. One reason: one or two people can change the outcome.
* Researchers often receive funding (or free juice) from producers, which may subconsciously affect their results ... and their ability to obtain more funding. (We've pointed out those studies, wherever possible.)
* Studies that come up empty are less likely to be published, so you usually see only the promising results.
One more caution: If you decide to add fruit juice to your medicine cabinet in a serious way, be prepared to add a notch or two to your belt. That's because people tend not to compensate for the calories they drink by eating less food later.
What's more, women in the Nurses' Health Study who drank an average of five servings of fruit juice a week had an 18 percent greater risk of being diagnosed with diabetes than women in the study who averaged 1 1/2 servings a week. (1)
If all of that hasn't made you toss your juice glass into the trash, here's a look at what researchers are finding out.
"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.
"When the PACs from cranberry juice are consumed, anti-adhesive compounds reach the bladder, where they can prevent the bacteria from attaching, or can weaken the attachment so that the flow of urine helps break the bacteria off the bladder wall and flushes them away," notes Howell, whose research is funded in part by the cranberry industry.
"Cranberry may help during the first 10 to 12 hours of an infection, when the bacteria are loosely bound," she adds.
Can drinking cranberry juice or taking cranberry pills prevent urinary tract infections?
In four studies reviewed by the Cochrane Collaboration, men and women who drank cranberry juice or took cranberry extract tablets for six months to a year were 34 percent less likely to have a urinary tract infection than those who took a placebo. (2) (The Cochrane Collaboration is an international network of scientists who evaluate the evidence behind different healthcare treatments.)
However, since the positive Cochrane analysis, a large trial involving more than 300 students at the University of Michigan reported that cranberry juice was no better than a placebo in preventing a recurrence of UTIs in women. (3)
Howell is skeptical of the findings. Among other things, "the researchers didn't verify that the women assigned to drink cranberry juice actually drank it regularly enough, such as by testing the women's urine for the presence of cranberry compounds," she says.
"College-age students are notorious for non-compliance in studies like this, and this was a long study, six months that they had to drink cranberry juice several times a day. It wouldn't be surprising if a lot of them didn't do it, but the researchers had no way of knowing."
In contrast, Finnish children who were treated for a urinary tract infection who were assigned to drink a cup of cranberry juice every day for a year--they didn't have a choice--had fewer subsequent UTIs and spent fewer days on antibiotics than similar children given a placebo drink. (4) An earlier study in Italian children found much the same. (5)
The Bottom Line: If you get recurring urinary tract infections, it's worth trying 8 to 10 oz. of cranberry juice cocktail or drink every day. But make sure it's at least 25 percent cranberry juice, which is what the clinical trials have used.
(A typical cranberry juice cocktail like Ocean Spray is 27 percent cranberry juice. Also at 25 percent or more: Knudsen Light, Lakewood Organic Light, and Old Orchard Naturals.)
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. (6)
In a British trial, 10 marathon runners who were told to drink 16 ounces a day of a cherry-and-apple juice blend for five days before a race, on the day of the race, and for two days afterwards didn't report less muscle soreness than 10 runners who drank a fruit-flavored placebo. But their bodies showed signs of less inflammation and they recovered their muscle strength faster. (7)
In a study funded by a cherry juice manufacturer and conducted by researchers with equity in the company, tart cherry juice also appeared to help people who were doing strength training.
Fourteen male college students drank either 24 ounces of tart cherry juice mixed with apple juice or 24 ounces of black-cherry-flavored Kool-Aid for four days before and four days after doing bicep-building exercises. The exercises were so strenuous that they produced pain and a temporary loss of strength in the arm. (8)
The young men reported less pain, and their temporary muscle loss was less, when they were drinking the cherry-apple juice.
Drinking cherry-apple juice will cost you, though; 16 to 24 ounces have roughly 300 to 400 calories. While it's possible that less juice would have worked as well, none of the studies looked. Nor have any studies looked at people who were doing less strenuous exercise.
Other juices may also help muscles recover from strenuous exercise, says David Nieman, director of the Human Performance Lab at the North Carolina Research Campus in Kannapolis, North Carolina, a private-public venture co-founded by the chairman of Dole Foods.
"I do not believe that the polyphenol profile in tart cherries is superior to that of other fruits and vegetables," he notes.
Just be prepared to drink for a while. "A one-to-three-week supplementation period prior to heavy exertion appears necessary for measurable effects," says Nieman.
The Bottom Line: If you're a serious athlete, you might consider drinking tart cherry juice to see if it helps you recover. Just make sure you can afford the extra calories.
"It is the magic elixir of our age and of all ages. And we know that it helps circulation, it helps Alzheimer's ... what it does for prostate cancer is amazing," pomegranate promoter Lynda Resnick declared on the "Martha Stewart Living" TV show in 2008.
Resnick and her husband, Stuart, launched the pomegranate juice craze ten years ago with their POM Wonderful brand. Since then, they have invested more than $30 million of their own money into research about the juice's potential health benefits.
They haven't been shy about promoting their juice with aggressive advertising that earned them a reprimand in 2005 from the Better Business Bureau and a lawsuit in 2010 by the Federal Trade Commission. The FTC accused the company of making "false and unsubstantiated claims that their products will prevent or treat heart disease, prostate cancer, and erectile dysfunction." The agency is asking the federal courts to restrict POM's health claims in advertising to only those approved by the Food and Drug Administration.
The billionaire Resnicks are fighting back, insisting that they have a First Amendment right to speak out and charging that the FTC is "wasting taxpayer resources" in going after them. The case is mired in the courts.
What's the evidence for pomegranate juice?
* Prostate cancer. 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. (9) (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.
A follow-up study in 180 similar men comparing two different doses of pomegranate juice with a placebo has been completed, but the results haven't been made public yet.
* Cardiovascular disease. Eight ounces of pomegranate juice every day for up to 18 months didn't slow down hardening of the arteries in men and women at risk of coronary heart disease. (10)
* Erectile dysfunction. Men in their 40s with mild to moderate ED fared no better after one month of drinking 8 ounces of pomegranate juice every day than they did after a month of drinking a placebo. (11)
The Bottom Line: Good human studies haven't demonstrated the benefits of pomegranate juice for prostate cancer, heart disease, or erectile dysfunction.
"Pretty much every berry we have studied--blueberries, strawberries, blackberries, and cranberries--has improved learning and memory in aging rats," says psychologist Barbara Shukitt-Hale of the U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston.
Shukitt-Hale and her late colleague Jim Joseph added different kinds of frozen berries to the diets of 19-month-old male rats, who are roughly equivalent to 65-year-old humans. Similar rats received the same basic diet, but with extra corn starch instead of berries. The amount of berries A was equivalent to about a cup a day for people. (12)
After two months, when the rats were the equivalent of 75- or 80-year-old humans, they were put in a pool of water, where they needed to learn and remember the location of a hidden platform so that they could solve the test and be removed from the maze.
"For a person, it's like remembering where you parked your car or figuring out how to get somewhere new," Shukitt-Hale explains.
The rats also had to balance on a horizontal rod that was rotating faster and faster, to test their motor skills. For humans, that might be like trying to walk on an uneven surface like icy pavement during winter.
"The rats who ate berries found the hidden platform more quickly and walked on the rods longer than similar rats who didn't eat berries," says Shukitt-Hale.
Some fruits helped with one skill but not the other, perhaps because each kind of fruit has its own profile of polyphenols.
Raspberries didn't help with memory, for example, but did with balance, while black currants improved memory but not motor function. And plum juice helped the rats' memories, but dried plums (prunes) didn't.
Trials to see whether fruit can help improve memory in humans are scarce.
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. (13) Welch's sponsored the study.
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. (14)
The Wild Blueberry Association and National Institutes of Health funded the study.
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.
The Bottom Line: 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.
The cells that line our small intestines contain an enzyme system called CYP3A, which metabolizes some drugs before they're absorbed into the bloodstream, explains David Greenblatt, professor of pharmacology and experimental therapeutics at the Tufts University School of Medicine.
When that happens, a portion of the drug is lost before it can start doing its job. Scientists take into account how much is lost when setting the recommended dosage for the drug.
Grapefruit juice contains a group of compounds called furanocoumarins, which knock out the CYP3A enzymes. So drinking the juice can lead to more of a drug's being absorbed than usual. (It takes three days for the inactivated enzymes to fully function again.)
There are only three prescription drugs that are likely to be affected enough to matter, says Greenblatt: the statin Zocor (simvastatin), the anti-hypertensive Felopidine, and the anti-anxiety Buspirone.
Greenblatt's advice: If you take one of them and want to drink grapefruit juice regularly, ask your healthcare provider if you should adjust the drug's dosage.
Do those three drugs also become more potent if you eat grapefruit rather than drink grapefruit juice?
"The part of the fruit that's eaten isn't rich in furanocoumarins," says Greenblatt. 'I don't know of any data indicating that eating whole grapefruit causes inhibition of CYP3A."
Buying a pricey, exotic tropical fruit juice is easy. Buying one that lives up to its health claims is pretty much impossible.
* Agai. There are no good human studies showing that acai juice can help regenerate muscles, bones, and blood or help people lose weight. And claims that acai's omega-3 fats are good for the heart are nonsense, since there's only a negligible amount in the fruit.
* Noni. People drink noni juice to treat cancer, heart disease, and diabetes, according to the National Center for Complementary and Alternative Medicine (NCAM), which is part of the National Institutes of Health. But "noni has not been well studied in people for any health condition," cautions NCAM.
* Mangosteen. Dealers claim that mangosteen juice boosts energy, kills pain, and lowers cholesterol. Yet there are no good studies in people showing that any of that is true.
(1) Diabetes Care 31:1311, 2008.
(2) Cochrane Database Syst. Rev. CD001321, 2008.
(3) Clin. Infect. Dis. 52: 23, 2011.
(4) Clin. Infect. Dis. (2011) doi: 10.1093/cid/cir801.
(5) Scand. J. Urol. Nephrol. 43: 369, 2009.
(6) J. Int. Soc. Sports Nutr. 7:17, 2010.
(7) Scand. J. Med. Sci. Sports 20: 843, 2010.
(8) Br. J. Sports Med. 40: 679, 2006.
(9) Clin. Cancer Res. 12: 4018, 2006.
(10) Am. J. Cardiol. 104: 936, 2009.
(11) Int. J. Impot. Res. 19: 564, 2007.
(12) J. Neurosci. 19: 8114, 1999.
(13) Br. J. Nutr. 103: 730, 2010.
(14) J. Agric. Food Chem. 58: 3996, 2010.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||SPECIAL FEATURE; healthy fruits|
|Publication:||Nutrition Action Healthletter|
|Date:||Mar 1, 2012|
|Previous Article:||Don't be dense: trim calories per bite to trim pounds.|
|Next Article:||Rebound fat.|