DOES IT WORKBilberry extract is said to improve eyesight, but this has not been proven
THE BILBERRY fruit is also called the European blueberry (Vaccinium myrtillus). The bush is commonly found in northern and central Europe, where the fruit has been a popular food.
More recently, bilberry extracts have become popular in treating a variety of eye problems. This reputation developed among RAF pilots during the second World War. Some pilots appeared to be able to see better when flying night bombing raids.
The only thing that seemed to explain the differences was that those with better night vision used bilberry jam. Soon, bilberries had a reputation for curing all sorts of eye problems, along with heart disease, varicose veins and several other conditions.
Evidence from studies
Bilberries contain a group of potent antioxidants called anthocyanins. Antioxidants are important nutrients that everyone needs.
The body normally produces waste compounds that need to be neutralised by antioxidants. Reduced intake of antioxidants is associated with an increased risk of several illnesses.
The best source is the recommended daily intake of a variety of fruits and vegetables.
Nonetheless, supplementation with additional antioxidants is commonly advocated.
In the case of bilberry, animal studies have found that the extracts positively affect blood flow in various tissues. They also make blood vessels less porous, which could reduce swelling and help with varicose veins. But such uses have not been confirmed in human studies.
The use of bilberry for night vision was supported by some studies carried out in the 1960s. However, since then, several larger and better-designed trials have found no benefit from bilberry.
A review of these and subsequent studies found that only one of the five high-quality trials found bilberry better than placebo for night vision.
Some benefit was found for people taking bilberry for retinopathy. This eye problem can develop in people with diabetes or high blood pressure. Further research is needed to confirm these preliminary findings.
Problematic aspects
Adverse reactions have not been reported in the studies of bilberry extracts. Given that the extracts may affect blood flow, anyone taking blood-thinning medications should be alert to possible bleeding problems.
Toxic reactions have been noted when people eat large amounts of the berries or consume them for long periods.
Up to 500mg of extract are recommended daily. Most studies used extracts containing 25 per cent anthocyanins, although the commercially available products vary in strength and quality.
Recommendations
Reports of bilberry helping with night vision point to the limitations of anecdotal reports and testimonials. The differences in night vision among the pilots could have been due to any number of factors.
Although the bilberry jam got the credit, controlled trials have shown that something else must have been the cause of any benefits.
However, by initiating research into bilberries, some potential uses for the extracts have been identified.
One of the most interesting of these is as a treatment for varicose veins. However, further studies are needed to verify whether such uses are valid.
Meanwhile, we know that bilberries are a good source of antioxidants, and can, therefore, be useful for general health as part of a balanced diet that is rich in plant foods.
Problems with vision or circulation can be due to even more serious underlying conditions. Therefore, anyone with symptoms of these problems should seek a medical evaluation and not try to self-medicate with bilberry.
Effective treatments for many of these conditions are readily available.
• Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
• If you would like a health product reviewed, e-mail healthsupplement@irish-times.ie