Research Review By Novella Martinello©

Date Posted:

September 2010

Study Title:

Berries: emerging impact on cardiovascular health

Authors:

Basu A, Rhone M, & Lyons TJ

Author's Affiliations:

Department of Nutritional Sciences, 301 Human Environmental Sciences, Oklahoma State University (OSU), Stillwater, Oklahoma, USA & Harold Hamm Oklahoma Diabetes Center, University of Oklahoma Health Sciences Center (OUHSC), Oklahoma City, Oklahoma, USA.

Publication Information:

Nutrition Reviews 2010; 68(3): 168-177.

Background Information:

Consuming fruits and vegetables is known to reduce the risk of developing cardiovascular disease. Recently, berries have become a popular choice, and for good reason. Types of commonly consumed berries include blackberry, black raspberry, blueberry, cranberry, red raspberry, and strawberries. Less commonly consumed berries include acai, black currant, chokeberry, and mulberries. Berries are low in calories, high in moisture and fiber, and contain natural antioxidants such as vitamins C and E, and micronutrients such as folic acid, calcium, selenium, alpha and beta carotene, and lutein.

There are about 400 individual anthocyanins in berries. They are generally more concentrated in the skins of fruits, especially berry fruits, with the exception of red berry fruits, and content is usually proportional to color intensity. This review describes the various effects of berries on cardiovascular health, using evidence from epidemiological trials and intervention studies, and the mechanisms through which they have these effects.

Summary:

Fruits and veggies, which are high in fiber and micronutrients, have been shown to significantly reduce risk of acute myocardial infarction. Unfortunately, a significant gap exists between the recommended daily amount of fruits and vegetables compared to the small amount that people actually consume.

Further, most people typically consume apples, pears, bananas, melons, citrus fruits, and grapes – berries are not as common a choice (US). There are significant associations between berries or berry flavonoids (anthocyanins) and cardiovascular health. Among men in an almost 13 year study, a higher berry intake was related to a lower risk of cardiovascular disease (CVD) (1).

Among women in a 16 year study, higher strawberry intake was related to a reduction in CVD mortality, higher blueberry intake was related to decreased coronary heart disease (CHD) mortality, and anthocyanin intake was coorelated with a reduced risk of CVD mortality in postmenopausal women (2). An 11-year study involving women found that the highest amount of intake of strawberries decreased CVD and elevated C-reactive protein (CRP) (3). CRP levels are associated with inflammation and are a risk factor for CVD. Overall, there is a potential anti-inflammatory role of berry flavonoids, which may contribute to overall reduction of CVD risk.

Intervention studies have suggested that acai berries, black currants, bilberries, boysenberries, blueberries, chokeberries, cranberries, lingon berries, raspberries, strawberries, and wolfberries can play a role in increasing plasma or urinary antioxidant capacity, decreasing LDL oxidation and lipid peroxidation, decreasing plasma glucose or total cholesterol, and increasing HDL-cholesterol – all important risk factors for CVD.

Berry consumption has also been shown to counteract postprandial metabolic and oxidative stresses that are associated with CAD (4,5). Studies using both conventional berry products or purified anthocyanin extracts with specific berries, such as bilberry and black currant extracts, chokeberry juice, cranberry extracts, and freeze-dried strawberries demonstrated favorable effects on plasma glucose or lipid profiles in subjects with metabolic risk factors including type 1 or type 2 diabetes mellitus, dyslipidemia, or metabolic syndrome (6).

Only two studies showed a significant decrease in systolic blood pressure: one was conducted with healthy men following cranberry juice supplementation and the other was in subjects with CVD risk factors following mixed berry supplementation. Berry intervention did not show effects on biomarkers of inflammation, with the exception of a significant decrease in adhesion molecules following cranberry juice supplementation in healthy volunteers.

Berry anthocyanins significantly decrease oxidative damage and inflammation, both of which play important roles in the progression of arthrosclerosis and CVD. Elderberry anthocyanins have shown cellular bioavailability and decreased cytotoxicity caused by chemical inducers of oxidative stress. Anthocyanins from blackberry extract were shown to protect against peroxynitrite-induced oxidative damage. Mulberry anthocyanins have also exhibited antioxidative and antiatherogenic affects.

Anthocyanins have shown effects related to reducing inflammation and blueberries have demonstrated protective effects against insulin resistance and hyperglycemia, thus reducing the risk factors for CVD. These studies show the potential of berries to ameliorate inflammation, glucose, and lipid abnormalities that contribute to CVD.

Nitric oxide (NO), when formed through activation of inducible nitric oxide synthase (iNOS), has proinflammatory effects, leading to increased vascular permeability, induction of inflammatory cytokines, and the formation of peroxynitrite, a strong oxidizing agent. Blackberry extract has demonstrated inhibitory effects related to NO biosynthesis.

While increased iNOS expression leads to the proinflammatory effects of NO, generation of NO by endothelial nitric oxide synthase (eNOS) generation of NO plays a crucial role in maintaining cardiovascular homeostasis by favorably modulating blood pressure and reducing endothelial dysfunction.

Berry anthocyanins have also been shown to affect lipid metabolism in models of dyslipidemia. Chokeberry juice has shown anti-hyperlipidemic effects and purified anthocyanins from blueberries and strawberries added to drinking water were shown to prevent the development of dyslipidemia and obesity in animal models.

Taken together, these studies suggest that berry anthocyanins may have cardioprotective effects by reducing oxidative stress and inflammation through effects on iNOS activity, interfering with carbohydrate digestion and reducing glucose absorption, favorably modulating dyslipidemia, and upregulating eNOS expression so as to maintain normal vascular function and blood pressure.

Clinical Application & Conclusions:

Berry intake can significantly reduce a variety of CVD risk factors. Consumption of fresh or frozen whole berries as part of a regular diet is better than intake of juices or extracts, which do not have the same nutritional profiles as whole berries. Encapsulated berry supplements may be suitable for the management of specific metabolic conditions, but encouraging the consumption of natural sources is always a good recommendation.

Additional References:

  1. Rissanen TH, Voutilainen S, Virtanen JK, et al. Low intake of fruits, berries and vegetables is associated with excess mortality in men: the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study. J Nutr 2003; 133: 199–204.
  2. Mink PJ, Scrafford CG, Barraj LM, et al. Flavonoid intake and cardiovascular disease mortality: a prospective study in postmenopausal women. Am J Clin Nutr 2007; 85: 895–909.
  3. Sesso HD, Gaziano JM, Jenkins DJ, Buring JE. Strawberry intake, lipids, C-reactive protein, and the risk of cardiovascular disease in women. J Am Coll Nutr 2007; 26: 303–310.
  4. Cao G, Russell RM, Lischner N, Prior RL. Serum antioxidant capacity is increased by consumption of strawberries, spinach, red wine or vitamin C in elderly women. J Nutr 1998; 128: 2383–2390.
  5. Paiva SA, Yeum KJ, Cao G, Prior RL, Russell RM. Postprandial plasma carotenoid responses following consumption of strawberries, red wine, vitamin C or spinach by elderly women. J Nutr 1998; 128: 2391–2394.
  6. Simeonov SB, Botushanov NP, Karahanian EB, Pavlova MB, Husianitis HK, Troev DM. Effects of Aronia melanocarpa juice as part of the dietary regimen in patients with diabetes mellitus. Folia Med (Plovdiv.) 2002; 44: 20–23.