BilberriesA Clinical Perspective

Bilberry (Vaccinium myrtillus) produces black berries with a slightly caustic and sweet taste. Bilberry is a rich source of phenolic compounds both in quantity and diversity of chemical composition. Fifteen anthocyanins have been characterized, which are various glucosides of cyanidin, malvidin, peonidin and petulidin. Total anthocyanidin content reportedly ranges from 23 to 30 mg/kg of dried weight. Among the phenolic compounds include the flavonoids quercitin, hyperin, rutin and diosmin, as well as several acids—caffeic, chlorogenic, ferulic, coumaric, syringic, OH-benzoic and OH-cynnamic. Bilberry has a rich chemistry and likely there is interplay among this constituent multiplicity associated to its health benefits.

Typical preparations are standardized to 25 percent anthocyanin content although more concentrated extracts exist. The preferred method for testing bilberry's quality and accurately representing its diverse chemical composition is via chromatography. Such methodology improves the consistency of any bilberry preparation and can spot potential adulteration.¹

Disturbing reports from Europe claim only 15 percent of commercial bilberry preparations actually contain sufficient quantities of anthocyanins to have a physiological effect.² Because the exact active constituent in bilberry is likely represented by a group of compounds that is not fully characterized as of yet, this presupposes for coherent and consistent evaluation of chromatography profiling of the anthocyanin bilberry constituency, rather than a single quantitative non discriminatory number as the total anthocyanin content.

Bilberries have been used for non specific diarrhea, venous insufficiency of the lower limbs, for varicose veins, hemorrhoid conditions, inflammation of the mouth, improving visual acuity and degenerative retinal conditions.³ Bilberry extract is marketed in Europe as a prescription drug for venous disorders and heavy legs.

Bilberry has been fairly well evaluated clinically relevant to its health benefits for the eyes and vision as well as for its overall vascular support.^4,5 While a recent systematic review examined 30 trials regarding visual acuity, and concluded bilberry anthocyanins do not support improvement of normal night vision;⁶ it was noted the studies lacked rigorous clinical evaluation of the effects of bilberry on subjects with actual impaired night vision due to their poor eye health conditions. In other words, the conclusion was based on outcomes derived from healthy individuals.

Further all trials that reported negative outcomes used low daily dosing, between 12 mg/d and 60 mg/d. More positive outcomes were seen in trials with significantly higher dosing, between 300 and 720 mg/d.

Regarding retinopathy due to diabetes complications, most studies demonstrate improvements in retinal function.^7,8,9 Notably, inconsistencies to the treatment persist; dosing for these studies varied appreciably, 320 to 600 mg/d, as well as the duration of treatment anywhere from 1 month to one year. Only three of these studies were placebo controlled.

The protective vascular activity of bilberry is attributed to its anthocyanin content, which exhibits specific affinity to capillary blood vessels of the eye and other vascular tissues. Anthocyanins bind with the phospholipids of the inner lining of blood vessels and increase the biosynthesis of proteoglycans, the basic constituents of the connective tissue of capillaries; and inhibit the activity of the proteolytic enzymes collagenase and elastase. Both of these effects result in capillary reinforcement and reduction of their permeability.

Such mechanisms of action, along with bilberry's antioxidant properties, reduce vascular inflammation. Further, bilberry anthocyanins induce nitrous oxide production, serving as a potent vascular dilator. Along with this vascular dilative action anthocyanins have also been clinically shown to exhibit antiplatelet aggregation.¹⁰

The combination of these mechanisms results in the following vascular benefits from bilberry:

Newer trials are examining whether bilberry’s vascular health benefits can work synergistically with other nutrients that are rich in polyphenol compounds. For example, one trial looked at a combination of bilberry and pine bark extract (180mg/80mg/d) dosing, which resulted in intraocular pressure decrease thus beneficial to glaucoma sufferers.¹¹

Dimitri Papadimitriou ([email protected]) is the sole owner of Arevno Consultants Corporation, specializing in dietary supplement formulations. He is currently serving as director of product development for Yasoo Health, a nutraceutical company that applies formulation technology to improve absorption of nutrients in disease-specific conditions known for their poor nutrient efficacy.

References on next page.

References for "Bilberry - A Clinical Perspective"

1. Penman KG et al. J Agric Food Chem. 2006;54(4):7378-82.

2. Cassinese C et al. J AOAC. 2007;90(4):911-19.

3. Natural Medicines Comprehensive Data Base, Published by Therapeutic Research Faculty, Stockton CA, 10th edition, 2008;155.

4. Virno M et al. Bolletino Oculistica. 1986;65(7-8):789-95.

5. Lee J et al. Br J Nutr. 2005;93(6):895-99.

6. Mindel J. Surv Ophthalmol. 2004;49(1):38-50.

7. Boniface R et al. Klin Monatsbl Augenheilkd. 1996;209(6):368-372.

8. Prossini M et al. Ann Ottalmol Clin Ocul. 1988;113(12):1173-1190.

9. Forte R et al. Ann Ottalmol Clin Ocul. 1996;122:325-33.

10. Pulliero G et al. Fitoterapia. 1989;LX(1):69-75.

11. Steigerwalt R et al. Molecular Vision. 2008;14:1288-92.