Written by Susan Sweeny Johnson, PhD, Biochem. DASH study shows correlation between a healthy diet emphasizing whole-grains and lowered blood pressure in subjects with and without hypertension.
Approximately 50 million Americans, including 30 percent of the adult population, have high blood pressure or hypertension. Untreated hypertension results in stroke or heart failure. Once a patient is diagnosed with hypertension, they often must maintain a continuous regimen of medication. These medications commonly have undesirable side effects. Therefore, delaying or preventing the onset of hypertension leads to a better quality of life.
Previous studies have shown a correlation between consumption of whole grains and a decrease in incidence of cardiovascular disease. (1, 2) The large study of dietary intervention for blood pressure control, the Dietary Approaches to Stop Hypertension (DASH) Trial, showed that a healthy dietary pattern emphasizing whole-grain cereal products substantially lowered blood pressure in subjects with and without hypertension. (3, 4) It should be noted that the association of refined-grain intake with blood pressure or risk of developing hypertension is much less consistent than for whole-grain intake.(5)
Whole grains contain a myriad of vitamins, minerals, phytochemicals, and other nutrients in the outer (bran) and inner (germ) layers. The bran and germ are both removed during the refining process, which makes refined grains more energy dense but less nutrient-rich than whole grains. In addition, whole grains contain much more dietary fiber, which has been associated in other large studies with decreased blood pressure. (6)
This new study used a self-reported dietary questionnaire to analyze the diets of 28,926 non-hypertensive women over 45 years old during the previous year. Out of this study group, 8722 women developed hypertension during the 10 year follow-up period. Their average weekly intakes of whole grain ranged from 0 to 15 servings per day. For the purpose of analysis the women were divided into five quintiles based on their average daily consumption of whole grains.
Quintile I: < 0.5 serving
Quintile II: 0.5 to < 1 serving
Quintile III: 1 to < 2 servings
Quintile IV: 2 to < 4 servings
Quintile V: > 4 servings
Compared to Quintile I, the number of women developing hypertension decreased moderately with increasing intake of whole grains, as shown below. The relative risks (RR) and 95% confidence intervals (CI) for developing hypertension were as follows (P for linear trend < 0.0001).
Quintile II: RR: 0.96 (CI: 0.90 – 1.03)
Quintile III: RR: 0.92 (CI: 0.86 – 0.99)
Quintile IV: RR: 0.90 (CI: 0.84 – 0.97)
Quintile V: RR: 0.86 (CI: 0.80 – 0.93)
No significant inverse correlation was observed when refined grain intake was compared with onset of hypertension.
The 2005 Dietary Guidelines from the US Department of Agriculture (USDA) recommend an intake of at least 3 whole-grain servings day and consumption of at least one-half of the total grain as whole grains. (7) In this study, a lower risk of hypertension began with whole-grain consumption of 1–2 and 2–4 servings per day or 43–58% of total grains as whole grains, consistent with the recommendations from the USDA.
The total direct cost for treating all cases of hypertension is estimated to be $10 billion annually. Medications comprise 70 percent of total treatment costs. Each individual being treated for hypertension, including office visits, laboratory tests, and medications, spends about $950 in the first year of treatment, $575 in the second year and $420 per year thereafter. Untreated hypertension results in stroke or heart failure. Hospitalization for heart failure is the most expensive single item in the Medicare budget costing over $12 billion annually. (8)
Source: Wang, Lu, J. Michael Gaziano, Simin Liu, JoAnn E. Manson, Julie E. Buring, and Howard D. Sesso. “Whole-and refined-grain intakes and the risk of hypertension in women.” The American journal of clinical nutrition 86, no. 2 (2007): 472-479.
© 2007 American Society for Nutrition
Posted August 11, 2008
References:
- Jacobs DR Jr, Meyer KA, Kushi LH, Folsom AR. Whole-grain intake may reduce the risk of ischemic heart disease death in postmenopausal women: the Iowa Women’s Health Study. Am J Clin Nutr 1998;68:248–57.
- Steffen LM, Jacobs DR Jr, Stevens J, Shahar E, Carithers T, Folsom AR. Associations of whole-grain, refined-grain, and fruit and vegetable consumption with risks of all-cause mortality and incident coronary artery disease and ischemic stroke: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Clin Nutr 2003;78:383–90.
- Appel LJ, Moore TJ, Obarzanek E, et al. A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. N Engl J Med 1997;336:1117–24.
- Sacks FM, Obarzanek E, Windhauser MM, et al. Rationale and design of the Dietary Approaches to Stop Hypertension trial (DASH). A multicenter controlled-feeding study of dietary patterns to lower blood pressure. Ann Epidemiol 1995;5:108–18.
- Steffen LM, Kroenke CH, Yu X, et al. Associations of plant food, dairy product, and meat intakes with 15-y incidence of elevated blood pressure in young black and white adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Am J Clin Nutr 2005;82:1169–77.
- Whelton SP, Hyre AD, Pedersen B, Yi Y, Whelton PK, He J. Effect of dietary fiber intake on blood pressure: a meta-analysis of randomized, controlled clinical trials. J Hypertens 2005;23:475–81.
- Dietary guidelines for Americans 2005. Washington, DC: US Department of Agriculture, 2005.
- National Quality Matters Clearinghouse website.
