The researchers used restraint of the animals to induce oxidative stress, and found that five days of supplementation with bilberry extract exerted a protective antioxidant activity, according to findings published in the Journal of Agricultural and Food Chemistry.
“Our results showed that bilberry extract attenuated oxidative stress by changing the oxidative status and improving antioxidative processes in mice subjected to stress,” wrote the authors from affiliated with two Chinese universities and Singapore’s Cerebos Pacific.
If the results can be repeated in humans, it could see bilberry extracts positioned as a potential supplement for people leading a stressful lifestyle.
Previous studies have shown that restraint of an animal promotes lipid peroxidation in liver tissue, said the researchers. This in turn leads to oxidative damage. Serious liver damage was observed in the new study following 18 hours of restraint of the mice. This was associated with increases in blood levels of alanine aminotransferase (ALT), and decreases in the oxidative activity of the blood, measured by the oxygen radical absorbance capacity (ORAC) values in the plasma.
Mice supplemented with an anthocyanin-rich bilberry extract (Mirtoselect, Indena) at doses of 50, 100, and 200 milligrams per kilograms per day experienced lower ALT levels than non-supplemented restrained animals (17.23 versus 107.68 units per litre, respectively).
Moreover, levels of malondialdehyde (MDA) - a byproduct of lipid peroxidation – were significantly lower in the bilberry-supplemented groups, said the researchers.
Blood levels of vitamin C were found to be significantly lowered following restraint of the animals, with free mice having average vitamin C levels of almost 400 micrograms per gram of tissue, compared to only 173 micrograms per gram in the stressed, un-supplemented animals.
Following supplementation with 100 or 200 mg per kg per day of the bilberry extract, vitamin C levels were measured at 347 and 451 micrograms per gram of tissue, respectively.
“This study showed the beneficial health effects of bilberry extract through its antioxidative action,” concluded the researchers.
Bilberries are closely related to the North American blueberry but contain a very distinct anthocyanin profile. Bilberry extracts are relatively expensive, with the price per kilo now estimated at around €600. Concerns are rife within the industry of lower-price extracts reported to be mixed with mulberry or black bean skins or azo-dyes.
Concerns were raised last year when Australian scientists discovered that azo dyes were used to mimic the colour of bilberries in a commercial product (J. Agric. Food Chem 2006, Vol. 54, Issue 19, pp. 7378 -7382). This has since expanded to reports of mulberry or black bean skins being used to increase the anthocyanin content of the extracts.
The anthocyanins content is used as the standard for bilberry, and UV spectrometry is needed to verify the 25 per cent anthocyanins. However, according to unconfirmed reports, this has led to extracts masquerading as bilberry but actually containing mulberry (22-24 per cent), or black bean skin (20 per cent).
Source: Journal of Agricultural and Food ChemistryVolume 56, Issue 17, Pages 7803-7807, doi: 10.1021/jf800728m“Protective Effects of Bilberry (Vaccinium myrtillus L.) Extract on Restraint Stress-Induced Liver Damage in Mice”Authors: L. Bao, X-S. Yao, C.-C. Yau, D.Tsi, C.-S. Chia, H. Nagai, H. Kurihara