Try Calorie Restriction to Live Longer?

Summarized by Robert W. Griffith, MD
March 13, 2006

Introduction

For many years there has been talk about the effect of calorie restriction on the age of laboratory animals. Could this be similar in humans, so that man would live longer if he ate less? It's taken some time for the studies to begin - maybe it's not so easy to find volunteers. But now a study has been published in the Journal of the American College of Cardiology that describes the effect of caloric restriction on cardiac function, which tends to decrease as we get older. Here's what was reported.

What was done

Twenty-five subjects who practiced calorie restriction for an average of 6½ years formed the test subjects. Their average age was 53, and 84% were male. As controls, 25 volunteers were recruited who were matched in gender and age with the test subjects.

The calorie restriction was quite severe. It consisted of roughly 1,670 calories a day divided into 23% protein, 49% complex carbohydrates, and 28% fat (6% as saturated fat). The controls ate a Western diet averaging 2,445 calories daily, with 17% protein, 52% carbs, and 31% fat (11% saturated). The calorie restricted diet contained 100% of the recommended daily allowances of all nutrients, and was low in salt. Vigorous physical activity was restricted in both groups to a maximum of 20 minutes twice a week.

Normally there is no obvious age-related change in systolic function, so measurements concentrated on tests of diastolic function¹. This was measured by a number of techniques, including Doppler echocardiography. In addition, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta-1 (TGF-beta-1) were measured as markers of inflammation of blood vessels.

What was found

During the course of the study the body mass index (BMI) fell in the calorie-restricted group from an average of 24 to 19.

The indicators of diastolic function were significantly better in the calorie-restricted group than in the controls. Doppler flow indexes were similar in the low-calorie group to those of younger individuals. The changes in diastolic function reflected increased heart chamber elasticity and decreased stiffness of the ventricle walls. Blood pressure, CRP, TNF-alpha and TGF-beta-1 were significantly lower in the calorie-restricted group, compared with the controls.

What this means

This is the first study to suggest that, in humans, fairly severe calorie restriction delays the aging process. Up to now, this way of slowing aging and increasing lifespan has been shown only in small mammals, like rats and mice.

Diastolic function is an accepted marker of aging because, as one gets older, diastolic function gets worse and worse, independently of disease. The lower inflammatory marker levels in the calorie-restricted subjects corresponded to those seen in younger healthy individuals. This suggests that inflammation may play a role in normal aging, or at least in aging of the cardiovascular system.

It's unlikely that many people will want to follow such a restrictive diet, no matter how healthy and possibly life-prolonging. As an editorialist points out, the value of this study lies in that it shows a possible mechanism by which aging occurs; and this, in turn, may suggest ways of modifying aging. Nevertheless, cutting your food intake is a 'good thing' for a number of reasons, even if you don't go as far as reduction to 1,600 - 1,700 calories a day!

Source

• Long-term caloric restriction ameliorates the decline in diastolic function in humans. TE. Meyer, SJ. Kovacs, AA. Ehsani,  et al., J Am Coll Cardiol, 2006, vol. 47, pp. 398--402

Footnotes
1. The cardiac cycle is divided into two parts - systole and diastole. During systole, the heart ventricles contract, ejecting blood out of the heart and into the arteries. Next, the ventricles relax, and re-fill with blood to prepare for the next contraction; this is called diastole. With increasing age, the ventricles become relatively "stiff." Stiff ventricles cannot fully relax during diastole, and as a result the ventricles may not fill completely; this is referred to as diastolic dysfunction.

Related Links
InfoAging: Calorie Restriction Information Center
The Longevity Meme: Calorie Restriction
Quality Counts: Anti-Aging Research Information

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