When You're Older, Your Muscles Need Antioxidants

Summarized by Robert W. Griffith, MD
April 23, 2004

Introduction

We know it's important for older people to be as physically fit as possible, and exercise programs for the elderly are getting more and more popular. But sometimes it seems to be a losing battle - the results are not as good as they should be. One possible factor may be age-related damage to the skeletal muscles by oxidative damage caused by so-called free radicals. (Free radicals are chemical substances that have unpaired electrons, which damage the major molecules that make up cells.)

Oxidative damage is thought to be responsible for the changes found with age in the brain, retina, and other vital organs. A group of Italian researchers has now investigated whether it's responsible for the reduction in muscle strength and physical performance that occurs in old age. Their findings are reported in the American Journal of Clinical Nutrition.

What was done

The subjects of the study were 986 Italian men and women over 65 who were taking part in the Invecchiare in Chianti Study. People who took vitamin supplements were excluded, along with those who couldn't provide detailed nutritional information or participate in the tests of physical function.

Knee extension strength in each leg was measured using a dynamometer. Physical performance was gauged on the basis of walking speed, standing up and sitting down unaided repeated five times, and balance while standing with various positions of the feet. The ability to perform these activities within a given period was summarized using a scoring system that's been shown to be a good predictor of mortality, hospitalization, and disability.

Blood levels of vitamin E (measured as alpha- and gamma-tocopherol) were determined to provide a measure of antioxidant status in the body. And all participants completed dietary questionnaires about different food categories and beverages, to supply the necessary information on their antioxidant intake - specifically vitamin C, vitamin E, beta-carotene, and retinol.

What was found

The average age of the participants was 75 years, and just over half of them were women. The most common health problems they had were high blood pressure (44%), diabetes (12%), cancer (10%), and coronary heart disease (7.5%).

The blood levels of alpha-tocopherol were correlated with the daily dietary intake of vitamin E -- i.e. individuals with high levels of one had high levels of the other, and vice-versa. Blood alpha-tocopherol was correlated with knee extension strength and the summary physical performance score, while gamma-tocopherol was only correlated with the knee strength test results.

When the dietary intakes were examined, it was found that vitamin C and beta-carotene intake were correlated with knee extension strength, and vitamin C intake with physical performance.

There were no differences between men and women in these findings.

What does this mean?

The analyses done show that higher plasma levels of antioxidants are linked to improved physical performance and strength in the elderly. Similarly, a higher intake of vitamin C and beta-carotene is associated with greater muscle strength.

How do the antioxidants work? Vitamin C and retinol are soluble in water and other body fluids, and represent first-line antioxidants; they inhibit lipid peroxidation, and act to 'regenerate' vitamin E in lipoproteins and cell membranes. Vitamin E and beta-carotene, on the other hand, are dissolved in lipids, and act by 'mopping up' the free radicals that do the oxidative damage. Both types of antioxidants are probably needed to do the job properly.

It must be remembered that this study was done in Italy, where olive oil consumption, and hence vitamin E, is considerably higher than in the USA. So, of course, it's natural to ask whether Americans should take vitamin supplements. For older people, it's probably not a bad idea. Up to 500 mg of ascorbic acid (vitamin C) and 400 IU of vitamin E can be taken without harm, and they may do some good if your diet is a bit lacking. There's no evidence, however, that taking large doses of vitamin supplements will help turn a weakling into a superman . . .

Source

• Antioxidants and physical performance in elderly persons: the Invecchiare in Chianti (InCHIANTI) study. M. Cesari, M. Pahor, B. Bartali,  et al., Am J Clin Nutr, 2004, pp. 289--294

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