People who restrict their caloric intake in an effort to live longer have hearts that function more like those in people who are 20 years younger.
Researchers at Washington University School of Medicine in St. Louis have found that a key measure of the heart's ability to adapt to physical activity, stress, sleep and other factors that influence the rate at which the heart pumps blood, doesn't decline nearly as rapidly in people who have significantly restricted their caloric intake for an average of seven years.
The study is available online in the journal Aging Cell.
"This is really striking because in studying changes in heart rate variability, we are looking at a measurement that tells us a lot about the way the autonomic nervous system affects the heart," says Luigi Fontana, MD, PhD, the study's senior author. "And that system is involved not only in heart function, but in digestion, breathing rate and many other involuntary actions. We would hypothesize that better heart rate variability may be a sign that all these other functions are working better, too."
The researchers hooked portable heart monitors to 22 practitioners of calorie restriction (CR) who ate healthy diets but consumed 30 percent fewer calories than normal. Their average age was just over 51. For comparison purposes, researchers also studied 20 other people of about the same age who ate standard Western diets. Heart rates were significantly lower in the CR group, and their heart rate variability was significantly higher.
"Higher heart rate variability means the heart can adjust to changing needs more readily," says lead author Phyllis K. Stein, PhD. "Heart rate variability declines with age as our cardiovascular systems become less flexible, and poor heart rate variability is associated with a higher risk of cardiovascular death."
Stein, a research associate professor of medicine in the Division of Cardiology, has measured heart rate variability in a number of different groups, from older adults to those with depression. This study was her first experience evaluating heart rate variability in the group often referred to as CRONies (Calorie Restriction with Optimal Nutrition), but members of that group have been studied extensively by Fontana, a research associate professor of medicine at Washington University and investigator at the Istituto Superiore di Sanita in Rome, Italy.
"The idea was to learn, first of all, whether humans on CR, like the calorie-restricted animals that have been studied, have a similar adaptation in heart rate variability," Fontana says. "The answer is yes. We also looked at normal levels of heart rate variability among people at different ages, and we found that those who practice CR have hearts that look and function like they are years younger."