July 2010 Issue

Blueberry Buzz — Research Investigates Supplements’ Effects in Multiple Health Conditions
By Jasmin Ilkay, MPH, RD
Today’s Dietitian
Vol. 12 No. 7 P. 18

July is reminiscent of vacations, fireworks, picnics, and pies. A patriotic dish wouldn’t be complete without a colorful splash of blueberries, especially since it is National Blueberry Month. These tangy, sweet berries are packed with vitamins A, C, E, and K; fiber; manganese; iron; and antioxidants. Researchers at the USDA Human Nutrition Center recently placed blueberries at the top of the list in antioxidant activity compared with 40 other common fruits and vegetables.

The high antioxidant ranking, latest studies, and limited availability of fresh blueberries have motivated dietary supplement companies to create a range of products, including blueberry juice, concentrated blueberry powder, blueberry tea, and blueberry extract. The assortment and popularity of these products corresponds with consumers’ increased recognition of the berry’s potential health value.

Phytochemical Framework and Potential Benefits
Blueberries are one of the few fruits native to North America and belong to the genus Vaccinium, which includes more than 450 species of plants (eg, cranberry, bilberry).

Blueberries’ health benefits are supposedly due to their unique assortment of phytochemicals, including various anthocyanins, chlorogenic acid, and resveratrol. The most abundant phytochemicals are the anthocyanins, the plant pigments responsible for blueberries’ deep blue-violet color. Anthocyanins reportedly have antioxidant and anti-inflammatory effects. Mainstream research regarding blueberries has focused primarily on their antioxidant activity, potential cancer-prevention properties, protective effects against dementia-related diseases, and link to urinary tract, heart, and vision health.

Heart Health
Results from the Women’s Health Study suggest that women who consume a diet high in anthocyanins have a significantly reduced risk of developing heart disease. Potential cardiovascular benefits of Vaccinium phytochemicals on the blood vessels are possibly related to decreased permeability, increased flexibility, decreased inflammation, decreased platelet aggregation, and general antioxidant activity.1 Most of these proposed effects are based on in vitro studies. However, a handful of human studies have confirmed the protective role of anthocyanins in heart disease and cholesterol management.

For example, a study published in the September 2009 issue of the American Journal of Clinical Nutrition focused on 120 people with dyslipidemia aged 40 to 65 who received 160 mg of anthocyanins extracted from bilberry and black currant or a placebo twice daily for 12 weeks. By the end of the trial, subjects receiving anthocyanin supplements had a 13.6% decrease in LDL and a 13.7% increase in HDL cholesterol.2 Cellular cholesterol efflux to serum increased by 20% in the anthocyanin group compared with 0.2% in the placebo group.2 The study authors note that the changes in lipid profiles observed in subjects receiving anthocyanins would result in a nearly 27.3% reduction in their risk of coronary heart disease.2

In terms of anthocyanins extracted from blueberries, a majority of the existing research is based on human dietary consumption of whole blueberries or various animal or in vitro studies. This research concurs with the idea that blueberry powder or anthocyanins extracted from the fruit can possibly prevent heart disease and/or manage cholesterol levels.

Urinary Tract Health
Like the related Vaccinium genus cranberry, blueberry supplements may have the capacity to reduce urinary tract pathogens.1 Researchers have proposed that anthocyanins may reduce bacteria’s ability to adhere to the mucosal lining of the bladder and urethra.1 Although blueberry supplements are new to most consumers, researchers have studied their effect on urinary tract health since the 1960s. Still, the actual benefits of fresh, juiced, or supplemental forms of blueberries for managing urinary tract infections remain uncertain.

Anthocyanins, particularly those from blueberries, have shown promise in treating dementia. Joseph and colleagues from the USDA Human Nutrition Research Center on Aging found that mice fed a blueberry supplement had enhanced memory performance and an increase in neuronal communication.3 The researchers proposed that the increase in neuronal communication offsets the negative effects of amyloid plaques in the brain. The results of this study excited researchers since they were able to demonstrate the possibility of overcoming the genetic predispositions to Alzheimer’s disease through blueberry supplementation.3

This study provides rationale to further investigate the effect of blueberry supplements on cognitive function and memory loss in humans. Investigators at the University of Cincinnati Academic Health Center conducted a study in which nine older adults consumed 2 to 2.5 cups of wild blueberry juice daily. Results showed a significant improvement in memory and learning test outcomes compared with the control group. Published in the Journal of Agriculture and Food Chemistry in January, the small study is one of the few human studies to validate blueberries’ memory-boosting potential.

Combined, these studies provide a strong basis for implementing a larger human clinical trial studying blueberries’ preventive effects and possible neuronal mechanisms.

Other Potential Benefits
The claim that blueberry supplements can treat visual problems is not based on any recent human clinical trials but on the vast amount of research on bilberry extract, prescribed in Europe to improve night vision.1

In terms of cancer prevention, most research involving blueberry supplements is based on in vitro and animal studies. The anthocyanin and ellagic acid antioxidants in blueberries may be the explanation behind cancer prevention.

Blueberry supplements also reportedly help with glycemic control in people with diabetes and can aid weight loss. These reports are largely based on studies of various Vaccinium species but not blueberries specifically. Therefore, researchers have suspected (but have not confirmed) that since blueberries are from the same genus, they may have similar effects.

Blueberry supplements appear to be safe for most people. However, people with diabetes should consult with their physician due to the supplements’ potential to lower blood sugar levels. No scientific information is available to determine an appropriate dosage, but the typical amount that dietary supplement manufacturers recommend is 1 T of dried powder, one tablet (containing anywhere from 200 to 400 mg of blueberry concentrate), or 8 to 10 tsp of blueberry concentrate liquid daily.

Complements, Not Substitutes
A majority of the data supporting these berry claims comes from epidemiological, in vitro, and animal studies. A handful of small human clinical trials also appears to support the healing potential of blueberries (and anthocyanins). Blueberry supplements cannot replace the nutritional value of whole blueberries, but adding blueberry powder or concentrate to a smoothie may offer complementary health benefits year-round.

— Jasmin Ilkay, MPH, RD, is a lecturer for the human nutrition and food science department at the California State Polytechnic University in Pomona and a freelance writer specializing in dietary supplements, child and family nutrition, and eating disorders.

1. Camire ME. Phytochemicals in the Vaccinium family: Bilberries, blueberries and cranberries. In: Meskin MS, Bidlack WR, Davies AJ, Omaye ST, Phytochemicals in Nutrition and Health. Boca Raton, FL: CRC Press; 2002: 19-40.

2. Qin Y, Xia M, Ma J, et al. Anthocyanin supplementation improves serum LDL- and HDL-cholesterol concentrations associated with the inhibition of cholesterol ester transfer protein in dyslipidemic subjects. Am J Clin Nutr. 2009;90(3):485-492.

3. Joseph JA, Shukitt-Hale B, Casadesus G. Reversing the deleterious effects of aging on neuronal communication and behavior: Beneficial properties of fruit polyphenolic compounds. Am J Clin Nutr. 2005;81(1):313S-316S.