The legend goes like this: British Royal Air Force pilots, after eating bilberry jam for tea, bombed the enemy during WWII with devastating accuracy, their night vision heightened by the powers of the inky blue fruit.
That story has never been confirmed -- and research hasn't turned up conclusive evidence of bilberry's ability to help you see in the dark.
Below are common symptoms associated with each eye problem.
Nearsightedness: Blurred vision that's worse when you are looking at distant objects suggests that you may be nearsighted, or myopic. People with myopia often have very good near vision.
Farsightedness: Blurred vision that's present when you are looking at near objects or, more commonly, near and far objects indicates that you may be farsighted, or hyperopic.
Astigmatism: Blurry vision can occur at any distance and usually...
Still, the dainty blue berry (Vaccinium myrtillus) continues to be an object of affection among scientists for its abundance of anthocyanosides, chemical compounds that have powerful antioxidant and anti-inflammatory properties.
And consumers still flock to bilberry extract, an enduring top-seller among herbal supplements, for its purported benefits to eye health.
"We've got this really sexy story, that it's good for night vision, but there's no evidence," says Evangeline Lausier, MD, clinical director of Duke Integrative Medicine, part of Duke University Health System in Durham, N.C. But because of the anthocyanosides in the fruit, "there are probably effects that make it part of a good diet.''
WebMD went hunting for the truth -- or lack thereof -- behind the claims for bilberry's healthfulness. Here's what we learned:
What Is a Bilberry?
The bilberry, a relative of the cranberry, huckleberry, and American blueberry, is a plant with bright green leaves and bell-shaped flowers that grows wild, primarily in northern Europe.
The bilberry looks very much like a blueberry, but its flesh is darker -- somewhere between deep purple and crimson -- and its flavor is tarter, says Steve Foster, a plant photographer who has written or co-written 17field and reference guides on medicinal plants and herbs, most recently National Geographic's Guide to Medicinal Herbs.
The depth of color of the bilberry's flesh is caused by those anthocyanosides -- also found in dark berries to varying degrees. The fruit also has antimicrobial tannins, which are found in purple grapes and dark teas.
In the 18th century, German doctors prescribed the bilberry for intestinal conditions, among other things. In the 20th century (1987), Commission E, the German panel of experts that assesses the safety and effectiveness of herbs, approved the use of bilberry extract for diarrhea and inflammation of the mouth or throat.
David Kiefer, MD, a research fellow in the department of family medicine at the University of Wisconsin in Madison, says it makes sense that bilberries have a reputation for helping conditions ranging from retinopathy (abnormal or damaged blood vessels in the retina) to diarrhea to heart disease.
"A lot of these [conditions] have an inflammatory component, so some herbs treat a variety of things," he says. "There's oxidative damage in so many illnesses. Whether in eye vessels or leg vessels, we can get a positive effect."
Kiefer says patients with macular degeneration -- the deterioration of the central part of the retina that can eventually cause blindness -- have reported that they use bilberry extract, with mild benefit, "but it's hard to sort out the anecdotal report from the placebo effect.''