Diet can do what pills cannot

GILAH KAHN-HOFFMAN ISRAEL21C

An Israeli study reveals that a healthy, long-term diet really does lower blood pressure and reverse clogging of the arteries – a major risk factor for stroke and heart attack.

“We can actually see the changes in the vessel wall volume that are caused only by diet,” said Dr. Iris Shai, lead researcher on the study. “For the first time, we have images that prove that a diet can accomplish what we believed could only be done with pills, and you get the same results with a low-carbohydrate or low-fat diet [otherwise known as] the Mediterranean diet.”

Shai, a researcher in nutrition at Ben-Gurion University (BGU), has spent the past two years studying the effect of diet on atherosclerosis (hardening of the arteries) and blood pressure – both of which are direct risk factors for strokes and heart attacks.

Her findings, which were published recently in Circulation, a journal of the American Heart Association, show that healthy, long-term weight-loss diets can significantly reverse carotid (main brain artery) atherosclerosis, and also lower blood pressure in overweight and mildly obese people.

“All the diets were different, but they had certain things in common,” Shai explained. “They all have an increase in vegetables, omit trans fats and processed food and cut calories. The common denominator of all the diets is moderate weight loss. It’s well known that people lose the most weight in the first six months of a diet and tend to gradually regain weight in the second six months. Our study shows that the main thing is to stick to the long-term, healthy diet strategy.

“Even if we experience some partial weight re-gain over time, long-term adherence to weight loss diets is effective ... as long as we stick to one of the current options of healthy diet strategy. This effect is more pronounced among mildly obese persons who lose more than 12 pounds of body weight and whose systolic blood pressure decreases by more than seven mmHg [millimetres of mercury],” she said.

Shai, who conducts research at the International Centre for Health and Nutrition in BGU’s department of epidemiology, worked with scientists from the Nuclear Research Centre in Dimona and Soroka University Medical Centre.

One hundred and forty moderately overweight people (mostly men) working at the Dimona nuclear centre in the Negev took part in the study. Each was put on one of three specific diet regimes – a low-fat diet, a low-carb diet or a Mediterranean diet.

The study required cooperation between staff, participants and their spouses. Along with workplace nutritional counseling, trial-participant spouses were educated on keeping to the diet strategy at home.

The scientists measured changes in carotid artery vessel thickening caused by plaque, to determine whether diet can reverse atherosclerosis, a process that naturally increases with age. They used a 3-D ultrasound imaging technique at the start of the study and, again, two years later. The findings show that, after two years, there was a five percent decrease in average carotid vessel wall volume and a one percent decrease in carotid artery thickness.

“One of the most interesting findings of the study is that we can actually see the changes in the vessel wall volume that are caused only by diet,” said Shai.

Dr. Yaakov Henkin, a cardiologist who led the carotid measurements, explained: “The importance of these results is in the understanding that, over two years, changes in carotid atherosclerosis are more strongly predicted by diet-induced changes in blood pressure than by changes in lipoprotein levels, which are commonly believed more important for the coronary arteries.”

“Lifestyle projects in the workplace might be a perfect platform for long-term successful interventions,” said Dr. Dan Schwarzfuchs, director of the medical clinic at the Dimona research centre, “as low-fat, low-carbohydrate and Mediterranean diets all induced regression of carotid atherosclerosis.”

This study was part of the Dietary Intervention Randomized Control Trial, the initial results of which were published in the July 2008 issue of The New England Journal of Medicine. Adherence to the study was 95 percent after the first year and 85 percent after the second, an unprecedented result in dietary intervention trials.

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