Diet alone can reduce CVD risk by 10% over a decade—more in women and Black adults

Sticking with either a diet high in fruit and vegetables or the Dietary Approaches to Stop Hypertension (DASH) diet can reduce the 10-year risk for atherosclerotic cardiovascular disease (ASCVD) by 10%. But the impact of the diets varies between the sexes and people with different racial ancestry. DASH worked notably better in women and Black adults. Taking a new look at data from the original DASH trial, researchers extrapolated what the 10-year risk of ASCVD would be based on the effects of the diets on biomarkers and other risk factors of study participants. Results were published in the American Journal of Cardiology. The DASH diet was compared to two other diets. The study was conducted because there is limited evidence to help inform what 10-year ASCVD risk reduction is really like from established lifestyle interventions, researchers wrote. Results from the DASH trial were published in 1997 and it was a three-arm, parallel-group, randomized controlled feeding trial. It compared the effects of three diets on blood pressure and included over 450 adults aged 22 to 75 years. Food was supplied. Read: QUIZ: Fighting hypertension with food Participants were randomized to one of three diets for eight weeks. The control diet was more of a typical North American diet which was high in total fat, saturated fat and cholesterol. The fruit and vegetable diet provided more produce, but otherwise differed little from the control diet. The DASH diet provided more fruit and vegetables, but it also includes more whole grains, lean proteins and nuts. DASH also uses low-fat dairy, and reduces overall fat, saturated fat, cholesterol and sugar. The results of the initial study found that in people with elevated blood pressure and hypertension, the DASH diet not only reduced systolic blood pressure (SBP), but it also decreased high-density lipoprotein (HDL) cholesterol levels compared to the control diet over eight weeks. It also showed that a comparator diet which was diet high in fruits and vegetables also reduced SBP, but not as much, and improved HDL cholesterol. However, the researchers noted that “the incremental benefit of the DASH diet compared with a simplified healthy diet emphasizing fruits and vegetables is unknown.” They conducted a study which used the eight-weeks’ worth of data from the study and extrapolated it to 10-year risk. The analyses considered details such as age, gender, race, ethnicity, total cholesterol, HDL cholesterol, SBP, diagnosis of diabetes mellitus, smoking, and whether individuals were treated for hypertension. Study coauthor Dr. Stephen Juraschek told the Medical Post: “This absolutely assumes people follow the diets rigorously.” He is an assistant professor of medicine at Harvard medical school. The analyses were limited to a subpopulation of 437 participants where there were complete BP and lipid data from both baseline and the eight-week follow-up visit. Overall, the mean age of participants was 45 years and about half were women and Black. Dr. Jurashek explained that: “Ten-year risk is estimated from the pooled cohort equation based on a single time point. It includes age, sex, race, blood pressure, lipid levels, diabetes status, current smoking status among other things. So, you only need a single point in time to estimate 10-year risk. . . . We calculated each person’s risk before and after the diets to determine change over eight weeks. We compared the changes between diets.” Overall, it was found that both the DASH diet and a diet high fruits and vegetable reduced 10-year ASCVD risk scores to a similar degree—a risk reduction of about 10%. However, it was found that the effects of the DASH diet were greater in women and Black adults. Women saw a 10-year risk reduction of nearly 13%, compared to just over 6% for men. And, DASH reduced the 10-year risk score by nearly 14% in Black adults, compared to three percent among non-Black adults. The researchers noted that while the DASH diet reduced risk factors associated with 10-year ASCVD risk (such as SBP and total cholesterol) more than the fruits and diet regime, the DASH diet also reduced HDL. And this is a finding that could increase estimated 10-ASCVD risk. “In contrast, the fruits and vegetable diet reduced SBP to a lesser degree but did not affect HDL, resulting in a similar net difference in overall ASCVD risk reduction as the DASH diet,” they wrote. The study is “an illustration of what can be achieved in the short term when all food is provided (as the eight-week trial did). It is not what you can expect in ten years of following a dietary prescription,” said Dr. David Jenkins. He is a professor of nutrition science and medicine at the University of Toronto and was not involved with the study. In the real world, people often can stick to a diet for maybe six months but not much longer, “certainly not for six years, or in this case 10 years,” he said. “The authors suggest that their work may inform patients decision on what diet to take based on their ten-year data. This impression should be dispelled.” The DASH diet conforms with advice given internationally to encourage a more plant-based diet and consume more fruit and vegetables (five to ten per day). But the downside is the advice has consistently been found difficult by the general public to follow. “If this paper encourages the public to consume more fruit and vegetables it will be useful. But it is no substitute for running a ten-year self-selected dietary trial.” Dr. Jenkins said.

Diet alone can reduce CVD risk by 10% over a decade—more in women and Black adults

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