A healthful dietary pattern may effectively turn back the clock for aging arteries and blunt the dramatic age-related rise in the prevalence of hypertension seen in the United States and other industrialized countries.
That’s been suspected for decades on the basis of epidemiologic studies. More than 80 years ago, for example, observers reported that German vegetarian Trappist monks didn’t experience the classic blood pressure rise with age, while German meat-eating Benedictine monks did (Med. Klin. 1930;25:929-31).
Only much more recently, however, have randomized controlled dietary trials been performed making the same point. The two most extensively studied and best-established of these healthful dietary patterns are the Dietary Approaches to Stop Hypertension (DASH) low-sodium diet and variations of the Mediterranean diet.
"To be provocative, you could say the DASH diet and low sodium abolishes 30 years of blood pressure aging in 4 weeks," said Dr. Frank M. Sacks, professor of cardiovascular disease prevention at the Harvard School of Public Health, Boston.
This was demonstrated when he and his colleagues randomized 412 subjects, ages 23-76, 41% of whom had stage 1 hypertension, to follow a DASH diet or a typical American diet for 90 days. During that period, subjects in each group were randomly assigned to a high-, intermediate-, or low-sodium diet for 30 days each in crossover fashion. Their weight was held constant by manipulating caloric consumption.
During the 30 days of high sodium intake (3.5 g per day), the slope for mean systolic blood pressure in the control group rose by 0.33 mm Hg per year of life.
In contrast, the slope for the DASH diet group while on a low-sodium diet of 1.2 g/day was 0 mm Hg per year. That is, mean systolic blood pressure during that month was 125 mm Hg in subjects in the oldest quintile, ages 55-76, and exactly the same in participants in the youngest quintile, ages 23-41 (Am. J. Cardiol. 2004;94:222-7).
"That’s because the effects of diet are much stronger in older people than younger people. The good effect of diet is stronger, but the bad effect is stronger, too," said Dr. Sacks, chair of the steering committee for the National Heart, Lung, and Blood Institute–sponsored DASH-Sodium trial.
Indeed, among study participants older than age 45 years with mild hypertension, the switch from the control diet with high salt intake to a month of the DASH diet with low salt intake resulted in a 15 mm Hg reduction in mean systolic blood pressure.
"That’s rather huge for a dietary therapy with no weight loss. The effect was about double the blood pressure reduction seen with the DASH diet and low sodium in the younger hypertensives," he notes.
The DASH diet is similar to what the American Heart Association recommends in guidelines for cardiovascular health and dietary management of hypertension (Hypertension 2006;47:296-308). The DASH diet emphasizes poultry, fish, nuts, and beans instead of red meat. It also makes extensive use of low- and non-fat dairy products, fruits and vegetables, and whole grains. A user-friendly website, www.dashforhealth.com, exists to help consumers get started. Other websites, for example, www.mayoclinic.com/health/dash-diet-recipes/RE00089, are a good source for cooking suggestions.
The traditional Mediterranean diet has much in common with the DASH diet. Dr. Sacks credits Dr. Katherine Esposito of the Second University of Naples and coworkers with having done much of the heavy lifting in terms of randomized trials. Most recently, Dr. Esposito and coinvestigators conducted a meta-analysis of 50 epidemiologic studies and randomized controlled trials of the effects of the Mediterranean diet on metabolic syndrome in more than 534,000 subjects.
The investigators demonstrated that adherence to the Mediterranean diet protected against the development of metabolic syndrome. Moreover, in patients with metabolic syndrome the diet significantly reduced both systolic and diastolic blood pressure, triglycerides, blood glucose, waist circumference, and inflammatory markers, while raising HDL (J. Am. Coll. Cardiol. 2011;57:1299-313).
In other work, Dr. Esposito and coworkers have shown in a randomized trial that adherence to the Mediterranean diet enabled one-third of obese men with erectile dysfunction to regain their sexual activity (Public Health Nutr. 2006;9:1118-20). A similar improvement in sexual function was documented in a separate 2-year randomized trial in women with metabolic syndrome and a diagnosis of female sexual dysfunction (Int. J. Impot. Res. 2007;19:486-91).
These improvements in sexual function presumably stem from the Mediterranean diet’s salutary effects on endothelial function (Am. J. Clin. Nutr. 2009;90:263-8). Similarly, the DASH investigators have shown that the DASH diet improves endothelial function in the microvasculature, notes Dr. Sacks.