Oct. 17, 2012 -- intro: For years, cranberry juice has been touted as the natural way to prevent and treat bladder and urinary tract infections (UTI). But a comprehensive review of studies has found the claims have been overhyped.

Certain sugars and a type of enzyme called flavanol found in cranberries have been thought to prevent infections by keeping bacteria from clinging to cells in the urinary tract.

Results from a review of 24 studies that included nearly 5,000 people suggest that cranberry juice may only be helpful in a select few women. Women with recurrent UTI are the most likely to benefit from cranberry juice. But regular women would need to drink at least two glasses of cranberry juice a day over a long period of time to prevent an infection, the researchers said.

However, it's unclear whether cranberry-based products such as pills may be able to offer more of a benefit than juice.

"More studies of other cranberry products such as tablets and capsules may be justified, but only for women with recurrent UTIs, and only if these products contain the recommended amount of active ingredient," said Ruth Jepson of the University of Stirling in the U.K., the lead researcher of the review.

While many people may not be ready to call it quits on cranberry juice just yet, the findings raise questions about whether the benefits of other foods we hear about are actually true.

quicklist: 1 category: Common Food Myths title: Caffeine Cures Headaches url: text: You might reach for that extra morning cup of java if you're looking for an energy boost.

But could the caffeine contained in that cup of coffee really provide a natural cure for a headache?

It may work for some of us but it's hard to tell exactly who will benefit from caffeine, says Keith Ayoob, director of the nutrition clinic at the Children's Evaluation and Rehabilitation Center at the Albert Einstein College of Medicine.

Some aspirin medications contain caffeine, which is known to speed the release of the medication into the bloodstream, to make them work faster.

"But it's not enough caffeine as what is found in coffee," Ayoob said.

In fact, consuming too much caffeine can lead to a caffeine withdrawal induced headache. So it might not be the surefire way to stop the pain. Talk to your doctor about whether caffeine could work for you, Ayoob said.

quicklist: 2 category: Common Food Myths title: Echinacea Prevents the Common Cold url: text: For many of us, the change of seasons can bring on the sneezes and stuffy nose. No matter how hard we try to prevent the common cold from ruining at least one good week, it always seems to find a way to settle in.

Of the many natural remedies that are offered as cures for the common cold, non may be more effective at preventing the viral infection than the herbal remedy Echinacea. A recent randomized study published in the journal Evidence-Based Complementary and Alternative Medicine found that those who took one 2400 mg of Echinacea extract per day over a 4-month period were able to ward off a cold.

Still, a majority of studies overall are not convincing about the protective effects of Echinacea.

There really is no tried and true medication or supplement yet that will ward off a cold, Ayoob said. Taking vitamin C at the hint of a cold is probably our best shot, according to Ayoob.

"The duration and severity may be minimized, but it won't prevent the cold," he said.

quicklist: 3 category: Common Food Myths title: Dark Chocolate Protects the Heart url: text: There is some truth to this. Cocoa contains antioxidants called flavonoids, which can help lower blood pressure. Chocolate has also been found to improve blood flow and won't raise cholesterol.

But that's not a license to treat yourself any more than once in a while.

Forget the idea of the more the better, because you don't need a lot of chocolate to produce the beneficial effects, Ayoob said.

Unfortunately, the chocolate bars regularly found on store shelves don't have high-enough cocoa content to provide adequate protection from heart-related problems.

"You get these effects at 70 percent cocoa or above," Ayoob said.

An ounce of dark chocolate is about 150 to 160 calories, and the darker the chocolate, the more heart-healthy it may be.

"If you have it as a dessert in place of cakes or others, it'll be lower calories and still good," said Ayoob.

quicklist: 3 category: Common Food Myths title: Warm Milk Treats Insomnia url: text: It sure works to help babies snooze, but how about as we grow older?

The truth is it could help you fall sleep better because it's warm and filling, not because it's milk.

Many may have thought warm milk was a sleep solution because it contains tryptophan, an amino acid that makes the hormone serotonin, which helps put us to sleep.

"But with milk you're getting a lot of other amino acids that are competing with the tryptophan," Ayoob said. "Tryptophan needs to be there on its own to get the full effect."

But that's no reason why we should stop drinking a glass before bedtime. Warm milk most likely works for some because it's warm and comforting. And unlike other hot products like tea or coffee, milk does not contain caffeine.

"It can take away the hunger pangs before you go to bed," Ayoob said. "An extra glass can fill the gaps of calcium."