BlueberriesA Clinical Perspective

There are about 16 species of blueberries (Vaccinium angustifolium) that are categorized as “superfruits.” They are extensively used in cooking, having a favorable combination of nutrient richness, antioxidant strength and health benefits.

Low bush (wild) and high bush (cultivated) blueberries are rich sources of phenolic acids, catechins, flavonols, anthocyanins and proanthocyanins. The concentration of these compounds in blueberries is affected in several ways, such as the level of maturity of the berries upon harvesting, cultivars, environmental conditions, storage conditions and processing procedures. Total phenolic content can vary from 191 to 376 mg/100 g and anthocyanin content varies from 118 to 163 mg/100 g; 

Anthocyanins with five different aglycons have been identified in blueberries present as galactosides, arabinosides and glucosides; blueberries also contain small quantities of the acetyl derivatives. Studies suggest a particular constituent in blueberries, pterostilbene, may help lower cholesterol and reduce inflammation.¹

One placebo-controlled clinical study using a mixed berry preparation that included blueberries showed a significant reduction in cholesterol at the end of four weeks.² Blueberries’ anti-inflammatory effects were also investigated in a clinical study involving 42 subjects diagnosed with Type 2 diabetes.3 Researchers found ingestion of a preparation of blueberry leaves rich in chlorogenic acid plus anthocyanin myricetin significantly reduced C-reactive protein (CRP) and other inflammatory enzymes.

Small clinical trials do support the antioxidant efficacy of blueberries. In one study, consumption of a single meal of blueberries (100 g freeze dried powder) increased plasma antioxidant capacity in the postprandial state.⁴ Trials have also shown ingesting blueberries can increase plasma antioxidant activity⁵ and reduce oxidative stress as measured by plasma biomarkers.⁶ Such effects were shown to be specific to the anthocyanin content of blueberries.⁷

Not all results have been positive. In one small clinical study, researchers failed to demonstrate any significant increase of antioxidant capacity in plasma when 500ml blueberry juice was given to healthy subjects.⁸ Yet another clinical study demonstrated consumption of blueberries (250 g/d) could reduce antioxidant stress in chronic cigarette smokers, but only when taken chronically (three week trial), not acutely.⁹ Such discrepancies may be in part attributed to individual genetic disposition, where some individuals appear to be more effectively protected from oxidative stress than others when ingesting blueberries.¹⁰

Recently, the media has reported on blueberries’ various health benefits, especially touting them as a “superfruit” for anti-aging, with a positive impact on brain aging, improving motor skills with aging and improving digestion of starch based foods.¹¹ While such findings again are yet to be proven in humans, USDA is currently investigating whether blueberries can modulate brain aging and cognitive decline.¹²

While the overall converging clinical evidence points to the multiple health benefits of blueberries, many such claims are yet to be proven clinically in humans and further research is needed to fully assess the health benefits of blueberry.

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

1. Pan MH et al. J Agric Food Chem. 2008;56(16):7502-9.

2. Abidov M et al. Georgian Med News. 2006;140:78-83.

3. Abidov M et al. Georgian Med News. 2006;141:66-72.

4. Kay CD et al. Br J Nutr. 2002;88(4):389-98.

5. Prior RL et al. J Am Coll Nutr. 2007;26(2):170-81.

6. McAnulty SR et al. Nutr Res. 2004;24(3):209-221.

7. Sanchez-Moreno C et al. Int J Food Sci Nutr. 2008;59(4):327-38.

8. Pedersen CB et al. Eur J Clin Nutr. 2000;54(5):405-8.

9. McAnulty SR et al. Free Rad Res. 2005;39(11):1241-8.

10. Wilms LC et al. Carcinogenesis. 2007;28(8):1800-6.

11. Lau FC et al. Subcell Biochem. 2007;42:299-318.

12. Lau FC et al. Neurobiol Aging Suppl. 2005;1:128-32.