Dietary Anthocyanins for Coronary Artery Disease: Berry Good Results
Abstract & Commentary
By Susan T. Marcolina, MD, FACP, Internist and Geriatrician, Issaquah, WA. Dr. Marcolina reports no financial relationships relevant to this field of study.
Synopsis: A multivariate analysis of a population-based study of 1898 women aged 18-75 years found that dietary intake of plant-derived anthocyanin pigments, primarily from grapes and berries, was associated with lower blood pressure readings as well as lower arterial stiffness determinations as measured by pulse wave velocities. This suggests that specific dietary phytonutrients may mitigate two important risk factors for coronary artery disease.
Source: Jennings A, et al. Higher anthocyanin intake is associated with lower arterial stiffness and central blood pressure in women. Am J Clin Nutr 2012; 96:781-788.
The authors performed a cross-sectional study to examine the association between the intake of dietary flavonoid subclasses, measured by the use of validated food frequency questionnaires, and in vivo measurements of blood pressure and arterial stiffness in a cohort of healthy female twins with a mean age of 46. The arterial stiffness was measured by means of the carotid to femoral pulse wave velocity (PWV) via a standardized system for which a normative database has recently been established, dependent on both age and blood pressure.1 The PWV has a large body of evidence that demonstrates its association with incident cardiovascular disease independent of traditional risk factors (hypertension, dyslipidemia, family history, smoking, and diabetes) in patient populations.2,3
Dietary flavonoids, classified as the plant pigments, are a diverse group of bioactive phytochemicals consumed in fruit, vegetables, and beverages such as tea, wine, and fruit juices. The anthocyanins are a class of these flavonoid compounds, which impart the dark blue, red, and purple colors to the berry fruits. Although a common basic chemical structure is shared by all classes of flavonoids, the differences in linkages, oxidation states, and functional side groups alter absorption, volume of distribution, metabolism, and bioactivity, which underscores the importance of investigating composite dietary flavonoid subclass intakes, as was done in this study.4
After adjustment for age, smoking, physical activity, body mass index, hormone replacement therapy use, statin and antihypertensive medication use, menopausal status, family history of hypertension or heart disease, use of vitamins, oral contraceptives, and intakes of energy (kcal/day) alcohol, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, fiber, and sodium, comparison of extreme quintiles of intake revealed that only a higher intake of the anthocyanin subclass of flavonoids was associated with significantly lower blood pressure (peripheral, central systolic, and mean arterial) and pulse wave velocities. The key results are listed in Table 1.
Table 1. Measures of Blood Pressure and Arterial Stiffness by Quintile of Anthocyanin Subclass Intake
The primary food sources of the anthocyanins consumed in this study were wine, grapes, and berries. There was an approximately 44 mg/day difference in intake between extreme quintiles of anthocyanin intake, which equates to approximately one to two portions of strawberries, grapes, blueberries, or raspberries (See Table 2).5
Table 2. Anthocyanin Content of Common Fruits5
The national health objectives outlined in Healthy People 2010 recommend at least two servings of fruit daily for people age 2 and older. Currently, however, only 32% of adults and 13% of adolescents comply with these recommendations.6,7
From a nutritional standpoint, there are several reasons to choose berries as part of a healthy diet. In addition to the anthocyanin content, berries also contain natural antioxidants such as vitamins C and E and the micronutrients folic acid, calcium, selenium, alpha- and beta-carotene, and lutein. They are also low in calories and high in moisture and fiber.8 Several dietary intervention studies9,10,11 with various types of berries have shown that berry consumption during meals significantly decreases postprandial oxidative stress, especially lipid peroxidation, which is associated with coronary artery disease.12
The most popular berries consumed in the United States are strawberries and blueberries. Cranberries, both as juice and juice blends, also are popular sources of dietary phytochemicals.13 The anthocyanin content of these and other varieties of berries can be quite variable and is dependent on the different cultivated varieties and growing conditions, although it is generally proportional to the intensity of the fruit color and increases with the ripening process. Since post-harvest processes such as freezing, pressing, and vacuum drying markedly decrease the anthocyanin content of the fruit, consumption of fresh fruit is desirable when possible.14,15
Conventionally grown strawberries, blueberries, and grapes, however, can be highly contaminated with organophosphate insecticides and have been included in the “Dirty Dozen” list of the Environmental Working Group’s 2012 Shopper’s Guide™.16 Organic cultivation of these fruits can mitigate this exposure. The higher price of organically cultivated fruits can be offset by prioritizing organic purchases to these specific fruits.
Two markers of arterial disease — blood pressure and arterial stiffness measured via the PWV method — were evaluated in this study. Arterial stiffness provides an assessment of both structure and function of the artery and is determined by dynamic factors such as sympathetic tone, blood pressure, and endothelium-derived vasodilators as well as intrinsic properties of the arterial wall such as wall thickness, relative collagen and elastin content, and degree of calcification.17
A recent database was established from a normotensive European population free from overt cardiovascular disease and diabetes and untreated with either antihypertensives or lipid-lowering drugs. They found that although PWV values increase with age from 6 m/s in normotensive (blood pressure > 120/80 mm Hg and < 135/85 mm Hg) subjects under 30 years to greater than 10 m/s after 70 years of age, this increase with age is more pronounced when the blood pressure increases. There was also considerable overlap of PWV values between younger and older subjects, possibly due to cardiovascular risk factors not quantifiable in the database such as family history. Although PWV is increasingly included in the assessment of patients involved in large-scale clinical studies, it is not yet available for routine clinical office because it is not clear how to use the reference data values to stratify patients’ cardiovascular risk.1
Current guidelines in the United States for the prevention and treatment of hypertension from the JNC-7 (Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure)18 promote the additional benefits of lifestyle modifications to antihypertensive drug therapy with a focus on the importance of the Dietary Approaches to Stop Hypertension (DASH) diet, which emphasizes increased daily consumption of fruit, vegetables, and low-fat dairy products.19
Although the cross-sectional design of this study precludes the ability to confer causality between dietary anthocyanin intake and lowering of blood pressure and arterial stiffness, additional prospective, controlled, randomized dietary intervention trials to investigate this association could result in more specific dietary recommendations as part of an overall public health strategy to reduce cardiovascular disease.
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