"This is the first study to show that this type of diet and exercise can reduce oxidative stress, lower blood pressure, and improve risk factors for other chronic diseases in a very short time," says R. James Barnard, Ph.D., senior author of the study and professor of physiological science at the University of California, Los Angeles.
Barnard and colleagues studied 11 obese (body mass index of 30 or greater) men aged 38 to 72, who voluntarily enrolled in the Pritikin Longevity Center 21-day residential diet and exercise program. Seven of the men had hypertension defined as a reading of over 140 millimeters of mercury (mm Hg) systolic or over 90 mm Hg diastolic.
The meals consisted of less than 10 percent of calories from fat, 15 to 20 percent from protein and 70 to 75 percent from unrefined carbohydrates. Carbohydrates were derived from five servings of high-fiber whole grains, four servings of vegetables and three servings of fruit daily. Grains, vegetable, and fruit were served all-you-want buffet style. The men had one serving of chicken or fish for dinner. The exercise program consisted of brisk walking on a treadmill for 45 to 60 minutes a day.
Blood samples were drawn for cholesterol, glucose and insulin measurements (all associated with heart disease) at the start and end of the program. The researchers also measured blood pressure, nitric oxide availability and oxidative stress. Nitric oxide helps prevent heart disease in several ways, including helping to relax blood vessels, thus reducing blood pressure. It also prevents cells in the walls of blood vessels from proliferating and clogging the arteries, a process that contributes to atherosclerosis. Oxidative stress refers to the presence of oxygen free radicals that can attack cells and tissues and contributes to cardiovascular disease and other health problems. By the end of the program, none of the seven hypertensive men had high blood pressure. Systolic blood pressure was reduced by 14 percent, diastolic blood pressure by 10 percent and oxidative stress by 28 percent, while nitric oxide availability improved by 28 percent. Total cholesterol decreased by 19 percent, insulin levels by 46 percent and blood glucose by 7 percent.
Although body weight and body mass index decreased slightly (about 4 percent each), the men were all still obese at the end of the three-week program.
The risk reduction occurs quickly, even if a person is still obese, he notes.
"You can lose weight over time, but fortunately, we can ease high blood pressure and the risk of atherosclerosis and heart disease while, or even before, you shed excess pounds," Barnard says.
Similar positive changes have been seen in non-obese people at risk for heart disease in other studies, he says.
"Within three weeks, we showed normalization of blood pressure and mitigation of other atherosclerotic risk factors, all of which will reduce the risk of chronic disease if kept up as part of a lifestyle change," says Christian Roberts, Ph.D., another of the study's authors.
"But if you return to an inappropriate diet and stop exercising, you will no longer benefit, and in fact you will regress," cautions Roberts, a postdoctoral fellow at UCLA.
Hypertension affects more than 50 million Americans age 6 and older, according to the American Heart Association.
Nosratola Vaziri, M.D. was the third coauthor of this study. The National Institutes of Health funded part of the study.