The Right Chemistry: Bilberries, blueberries and night vision

As the story goes, British pilots in the Second World War ate bilberry jam to improved their night vision. Well, it’s a good story …

When it comes to evaluating dietary supplements, the challenge is to find some clarity when looking through the haze of conflicting studies, sloppy research, over-zealous advertising and loose government regulations. Extracts of blueberry and its European cousin the bilberry, are a case in point.

It starts with a compelling legend. As the story goes, British pilots used bilberries to shoot down German fighters during the Second World War. They didn’t fire them out of their guns. They ate them. In the form of jam. This is said to have improved their night vision and made them more successful in dogfights. However, there is no evidence that they had improved vision, nor that they ate bilberry jam. An alternate account is that the rumour was spread by the military to distract the Germans from the fact that the British were testing radar equipment in their planes. An interesting possibility, but this too lacks evidence. In some versions of the story, the pilots’ success was attributed to eating carrots.

While the dietary habits of the Second World War pilots are debatable, the supposed benefits of bilberries for the eyes did arouse researchers’ interest. That’s because these berries have a folkloric history for treating ailments ranging from circulatory problems to diarrhea and ulcers. And there is some rationale for possible benefits, since bilberries and blueberries are rich in anthocyanins, the pigments responsible for their colour. Anthocyanins have antioxidant properties and are capable of neutralizing the notorious free radicals that are generated as a byproduct of normal metabolism and are suspected of playing a role in sparking various diseases.

Bilberries and blueberries have similar anthocyanin content, with the highest concentration found in the skin. However, there is nothing special about bilberries. Some cultivars of blueberries actually have a greater antioxidant effect than bilberries, but this has no practical significance.

Two research groups, one at the Naval Aerospace Research Laboratory in Florida and the other at Tel Aviv University decided to see whether there was any real science behind the myth of the British pilots’ boosting their visual acuity with bilberry jam. In both cases, young men were given either a placebo, or extracts that contained up to 40 mg anthocyanins, an amount that could be reasonably consumed from berries in the diet. Various tests to measure night visual acuity were administered, and in both cases, the conclusion was that no improvement in night vision was seen.

Blueberry and bilberry extracts are also promoted as dietary supplements to help reduce the risk of macular degeneration, the irreversible condition that occurs when the macula, the central portion of the retina, deteriorates. The retina is the tissue at the back of the eye that detects light. In theory, based on laboratory experiments, antioxidants can afford protection. When retinal cells are exposed to hydrogen peroxide, a strong oxidant, they suffer less damage when bathed in a blueberry anthocyanin extract. That, however, is light years from concluding that dietary anthocyanin supplements can help with macular degeneration. No clinical trials have examined the effects of anthocyanin supplements on macular degeneration so that right now there is no basis for recommending berry extracts for any eye problem.

The supposed benefits of bilberry and blueberry extracts are not restricted to vision. Anthocyanins are found in numerous fruits and vegetables, raising the possibility that they may be one of the reasons why consuming an abundance of plant products contributes to good health. Indeed, some epidemiological studies have shown that an intake of anthocyanin-rich foods such as blueberries are associated with a reduced risk of heart disease. However, such an association cannot prove that the berries offer protection since people who eat lots of berries may have very different lifestyles from people who do not.

In order to establish a cause-and-effect relationship, an intervention study is needed, whereby subjects consume blueberries and various markers for health are monitored. A study by researchers at King’s College in London did just that by investigating the effects of blueberry consumption on the health of arteries. A small group of healthy volunteers was asked to consume a daily beverage made with 11 grams of wild blueberry powder, roughly equivalent to 100 grams of fresh wild blueberries. Blood pressure was regularly monitored, as was the “flow-mediated dilation (FMD)” of the arteries in the subjects’ arm. This is a measure of how readily arteries widen as blood flow increases and is a predictor of the risk of heart disease. After a month there was a significant improvement in FMD as well as a lowering of systolic blood pressure. Interesting, but not evidence of actual reduction in heart disease. Similar, although somewhat reduced effects were found when a mix of pure anthocyanins, the equivalent to the amount in the beverage (160 mg), was consumed. It seems that blueberries have some other beneficial components other than anthocyanins as well.

Incorporating blueberries into the diet is a good thing to do, but anyone claiming that extracts can improve vision is looking through rose-coloured glasses.

Joe Schwarcz is director of McGill University’s Office for Science & Society ( He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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Post time: Jul-02-2019