People who keep up their low-calorie diets may be able to count on more than their waistline shrinking: A new study suggests that the heart's diastolic blood pressure goes down, too. The results bode well for the theory that such diets can prolong lifespan in humans, as dieters' hearts worked as well as those of individuals on a calorie-packed western diet who were 15 years younger.
Previous research has shown that caloric restriction increases the lifespans of mice, fruit flies, and the tiny worm Caenorhabditis elegans (ScienceNOW, 2 March 2005). Mice on such diets show improved heart function, indicating caloric restriction may improve longevity by keeping the heart in good shape. Whether the same applies to humans, however, remained unclear.
To explore the issue, gerontologist Luigi Fontana of Washington University in St. Louis, Missouri, and his colleagues recruited 25 subjects who had been practicing caloric restriction for an average of 7 years. Compared to 25 additional volunteers on a typical western diet, the caloric restrictors consumed nearly half as much saturated fat, 30% less salt, and an average of about 750 fewer total calories per day.
Heart activity differed almost as drastically. When the researchers compared the current diastolic function (how well the heart relaxed between beats) of the caloric restrictors against both their prediet figures and those of the western dieters, they found that the diastolic blood pressure of the caloric restrictors had dropped an average of 22 points--or about 25%--from their prediet pressure; the same drop was seen between caloric restrictors and western dieters. In addition, compared to western dieters, caloric restrictors had signs of less inflammation and fewer markers of fibrosis--both considered to be mechanisms of aging.
The results indicate that the same mechanisms that slow the aging process in mice may be at work in people, says Fontana, whose team reported its findings 17 January in the Journal of the American College of Cardiologists. Still, he says, because the study was not randomized, the team cannot claim that a calorie restrictive diet directly leads to improved diastolic function.
The study also does not indicate whether people on a caloric restrictive diet have younger looking hearts because the diet keeps their hearts in prediet shape or because caloric restriction alters their physiology to make their hearts work at more youthful levels, says biochemist Stephen Spindler of the University of California in Riverside. "This is an important distinction," he says, "because we would like to know if older people can begin such a diet and reap the benefits."