Study Overview
Objective. To examine the association of individual fruit and vegetable intake with the risk of developing hypertension.
Design. Meta-analysis.
Setting and participants . Subjects were derived from the Nurses’ Health Study ( n = 121,700 women, aged 30–55 years in 1976), the Nurses’ Health Study II ( n = 116,430 women, aged 25–42 years in 1989), and the Health Professionals Follow-up Study ( n = 51,529 men, aged 40–75 years in 1986). Participants returned a questionnaire every 2 years reporting a diagnosis of hypertension by a health care provider. Participants also answered qualitative–quantitative food frequency questionnaires (FFQs) every 4 years, reporting an intake of > 130 foods and beverages. Participants who reported a diagnosis of hypertension at the baseline questionnaire were excluded from the analysis.
Main outcome measures . Self-reported incident hypertension.
Results. Compared to participants whose consumption of fruits and vegetables was ≤ 4 servings/week, those whose intake was ≥ 4 servings/day had multivariable pooled hazard ratios for incident hypertension of 0.92 (95% confidence interval [CI], 0.87–0.97) for total whole fruit intake and 0.95 (CI, 0.86–1.04) for total vegetable intake. Similarly, compared to participants who did not increase their fruit or vegetable consumption, the pooled hazard ratios for those whose intake increased by ≥ 7 servings/week were 0.94 (0.90–0.97) for total whole fruit intake and 0.98 (0.94–1.01) for total vegetable intake. When individual fruit and vegetable consumption was analyzed, consumption levels of ≥ 4 servings/week (as opposed to < 1 serving/month) of broccoli, carrots, tofu or soybeans, raisins, and apples were associated with lower hypertension risk. String beans, brussel sprouts, and cantaloupe were associated with increased risk of hypertension.
Conclusion. The study findings suggested that greater long-term intake and increased consumption of whole fruits may reduce the risk of developing hypertension.
Commentary
Hypertension is a major risk factor for cardiovascular disease and a growing public health concern. Effective public health interventions that will lead to population-wide reductions in blood pressure are needed. The adoption of a healthy diet and low sodium intake is recommended by the American Heart Association in order to prevent hypertension in adults [1]. However, specific information about the benefits of long-term intake and individual foods is limited.
This study aimed to examine the association of individual fruit and vegetable intake with the risk of developing hypertension in 3 large prospective cohort studies in the United States. It was found that greater long-term intake and increased consumption of whole fruits may reduce risk of developing hypertension. Participants with higher fruit and vegetable intakes were more physically active, older, had higher daily caloric intakes, and were less likely to be smokers.
This study was novel in that it examined individual fruit and vegetable consumption. All 3 studies provided a large sample, which increased precision and power in the statistical analysis. Researchers were focused on establishing an association between the risk of hypertension and fruit and vegetable consumption; therefore, hazard ratios were presented and Cox regression and multivariate analysis were used, which are appropriate statistical methods for this type of study.
Some limitations should be mentioned. Blood pressure was not directly measured. Food intake was measured using a dietary questionnaire and may not have accurately represented actual intake. Also, participants were mostly non-Hispanic white men and women and other population groups were not well represented.
Applications for Clinical Practice
Reducing the risk for hypertension by increasing fruit consumption needs to be examined in other population groups and studies. In the meantime, clinicians can continue to recommend an eating plan that is rich in fruits, vegetables, and low-fat dairy products and reduced in saturated fat, total fat, and cholesterol.
—Paloma Cesar de Sales, BS, RN, MS