Reference
Riso P, Klimis-Zacas D, Del Bo' C, et al. Effect of a wild blueberry (Vaccinium angustifolium) drink intervention on markers of oxidative stress, inflammation and endothelial function in humans with cardiovascular risk factors. Eur J Nutr. 2012 Jun 26. [Epub ahead of print]
Design
Randomized, controlled trial with crossover
Participants
Eighteen male volunteers [ages 47.8 ± 9.7 years; body mass index 24.8 ± 2.6 kg/m2].
Study Medication and Dosage
Participants consumed either a drink made from 25 g freeze-dried blueberry powder or placebo each day for 6 weeks. After a 6-week washout the groups were switched. The blueberry drink contained 375 mg of anthocyanins (ACNs) per serving.
Primary Outcome Measures
Markers of oxidative stress, inflammation, and endothelial function, including endogenous and oxidatively induced DNA damage in blood mononuclear cells, serum interleukin levels, reactive hyperemia index, nitric oxide, soluble vascular adhesion molecule concentration and other variables were analyzed.
Key Findings
Consuming the wild blueberry drink significantly reduced the levels of endogenously oxidized DNA bases (from 12.5 ± 5.6% to 9.6 ± 3.5%, P≤0.01) and the levels of H2O2-induced DNA damage (from 45.8 ± 7.9% to 37.2 ± 9.1%, P≤0.01), while no effect was found after the placebo drink.
Practice Implications
People who are interested in staying healthy want to avoid oxidized DNA bases, which lead to mutations.1 Mutations lead to cancer. The impact of eating blueberries found in this study is a good thing.
We can add this study to our growing pile of interesting randomized clinical trials in humans that have investigated blueberry or blueberry extracts for a range of conditions. Blueberries appear to be an effective way to improve antioxidant status and protect against oxidative injury.
A study published in August 2007 in which 168 volunteers drank a daily glass of blueberry/apple juice for a month found that plasma quercetin, ascorbic acid, and trolox equivalent antioxidant capacity (TEAC) were significantly increased. The researchers reported a 20% protection (P<0.01) against ex vivo hydrogen peroxide-provoked oxidative DNA damage.2
Blueberries appear to be an effective way to improve antioxidant status and protect against oxidative injury.
An October 2010 paper published in Nutrition Journal reported that chemicals in blueberries improve insulin sensitivity in obese, insulin-resistant men and women. In this double-blinded, randomized, controlled trial, 15 obese volunteers drank smoothies twice a day, each of which contained 22.5 grams of blueberry ‘bioactives,’ while a control group consumed similar smoothies but without the blueberries. Insulin sensitivity improved more in the blueberry group than in the placebo group. The daily dose of ‘bioactives’ consumed by these study participants contained 668 mg of anthocyanins and was equivalent to approximately 2 cups of fresh whole blueberries.3
In April 2010 researchers from the University of Cincinnati reported that 9 older adults who drank a daily serving of wild blueberry juice had significant improvements in cognitive function, including paired associate learning and word list recall. They also tended toward a reduction in depressive symptoms.4
In December 2011, Italian researchers reported that regular consumption of a blueberry drink improved intestinal flora. After 6 weeks Bifidobacterium spp. significantly increased.5
Another paper of interest was published in December 2011. It was written McAnulty et al from Appalachian State University, a research group that specializes in measuring the oxidative impact of strenuous exercise. This study examined the impact of eating 250 g of blueberries per day for 6 weeks and then eating 375 g an hour before a long, hard run (2.5 hours at 72% maximal oxygen consumption). Twenty-five well-trained athletes took part in the study. Compared to a control group who went through the run, the blueberry group had increased natural killer NK counts. Even a single dose of blueberries eaten just before the run reduced oxidative stress and increased anti-inflammatory cytokines.6
An interesting trial was published in September 2012, using rats rather than humans. The rats were fed a diet high in fructose to trigger metabolic syndrome. Adding blueberry ‘pomace’ to their diet provided protection, reducing plasma cholesterol and abdominal fat relative to the HF control, which may impart additional health benefits. Pomace is the solid material left after expressing juice from a fruit. An excellent source of fiber and anthocyanins, fruit pomace is often considered "compost hoping for a better purpose."7 We should expect to find blueberry pomace ‘extracts’ to find their way into nutritional supplements and nutraceutical foods.
Given the number and variety of benefits seen in these studies, it is ever more prudent for us to encourage our patients to consume blueberries. Form doesn’t seem to matter; fresh fruit, juice, freeze-dried, or pomace, blueberries in any form appear to have beneficial impact.
