by Craig Weatherby
The phyto-chemicals that give autumn leaves and berries their blue-red colors are known as anthocyanins.
Anthocyanins are a subclass of the common, food-borne polyphenol compounds known as flavonoids, which are associated with myriad health benefits in the human body.
Polyphenols influence the expression of our genes… including ones that control inflammation and the body's own antioxidant network (see today's companion article, “Magnesium's Anti-Diabetic Gene Effects”).
Gene expression is a process in which a gene is “switched on” and commands a cell to take certain actions—such as assembly of messenger proteins or RNA—that initiate or influence bodily processes.
Based on lab studies and preliminary clinical research, the anthocyanins in berries appear to exert nutrigenomic effects that benefit immune and brain health, support sugar metabolism, moderate inflammation, and reduce oxidative stress from free radicals (Seeram NP 2010; Prasad S et al. 2010).
Now, an analysis by scientists from Harvard University and the UK's University of East Anglia indicates that berry-borne anthocyanins—which most study participants got from blueberries and strawberries—may help prevent high blood pressure.
High blood pressure (hypertension) is defined as having a systolic and diastolic blood pressure greater than 140 and 90 mmHg, respectively.
Analysis of health professionals' studies links berries to blood pressure
The study involved analysis of data collected from 156,957 health professionals… 133,914 women from the Nurses' Health Study I and II and 23,043 men from the Health Professionals Follow-Up Study.
Their intakes of anthocyanins and other flavonoids were calculated based on their answers to diet surveys conducted every four years (Cassidy A et al. 2011).
The nurses and doctors who reported eating the most berries—hence, the most anthocyanins—were about 12 percent less likely to have developed high blood pressure during the 14 years of the study period.
And, compared with those who reported the lowest intakes (5.7 to 6.8mg per day) the health professionals who reported the highest average anthocyanin intakes (16.2 to 21.0mg per day) were eight percent less likely to have developed hypertension.
Those benefits increased to a 12 percent reduction in risk among berry-loving health professionals over the age of 60.
No other classes of flavonoids were associated with reduction in the risk of hypertension, exceptthat one called apigenin—found in chamomile and thyme—was associated with a five percent reduction in risk, when comparing the highest with the lowest average intakes.
And, of interest to people who like tea and cocoa, people over 60 with the highest average intakes of catechin-class flavonoids (i.e., flavan-3-ols) were 6 percent less likely to develop hypertension.
In terms of whole berries themselves, people over 60 who reported eating more than one serving of blueberries per week were 10 percent less likely to develop hypertension, compared with people in the same age group who ate none.
As with any epidemiological study, the results cannot prove that anthocyanins reduce the risk of hypertension.
But as the authors wrote, “These findings warrant further investigation, including intervention studies designed to test optimal doses of anthocyanin rich foods for the prevention of hypertension and to underpin guidelines for the prevention and treatment of hypertension” (Cassidy A et al. 2011).
In other words, doctors should probably be advising most of their hypertension patients to eat more berries.
Why would anthocyanins help?
The benefits of berries seem to have a great deal to do with the health of our arteries.
As they wrote, “The underlying biological mechanisms by which flavonoids regulate blood pressure include the effects of flavonoids on vascular blood flow, vascular reactivity, and glucose uptake” (Cassidy A et al. 2011).
Growing evidence suggests that, instead of benefiting arteries through direct antioxidant effects, anthocyanins seem to regulate the amount of nitric oxide in the endothelial lining of our arteries (Nitric oxide is essential to keeping arteries open).
Dr. Rimm and his co-workers noted that an average serving of blackcurrants or blueberries contains in excess of 500 milligrams of anthocyanins.
Cassidy A, O'Reilly ÉJ, Kay C, Sampson L, Franz M, Forman JP, Curhan G, Rimm EB. Habitual intake of flavonoid subclasses and incident hypertension in adults. Am J Clin Nutr. 2011 Feb;93(2):338-47. Epub 2010 Nov 24.
Corti R, Flammer AJ, Hollenberg NK, Lüscher TF. Cocoa and cardiovascular health. Circulation. 2009 Mar 17;119(10):1433-41. Review.
Kim JA. Mechanisms underlying beneficial health effects of tea catechins to improve insulin resistance and endothelial dysfunction. Endocr Metab Immune Disord Drug Targets. 2008 Jun;8(2):82-8. Review.
Prasad S, Phromnoi K, Yadav VR, Chaturvedi MM, Aggarwal BB. Targeting inflammatory pathways by flavonoids for prevention and treatment of cancer. Planta Med. 2010 Aug;76(11):1044-63. Epub 2010 Jul 15. Review.
Seeram NP. Berry fruits: compositional elements, biochemical activities, and the impact of their intake on human health, performance, and disease. J Agric Food Chem. 2008 Feb 13;56(3):627-9. Epub 2008 Jan 23.