Fruits & Veggies Preserve Muscle Mass

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Plant Foods for Preserving Muscle Mass

By lie n Bliss

May 23, 2008

Fruits and vegetables contain essential vitamins, minerals and fiber

that are key to good health. Now, a newly released study by Agricultural

Research Service (ARS)-funded scientists suggests plant foods also may

help preserve muscle mass in older men and women.

The study was led by physician and nutrition specialist Bess

Dawson- at the Mayer USDA Human Nutrition Research Center on

Aging at Tufts University in Boston, Mass.

The typical American diet is rich in protein, cereal grains and other

acid-producing foods. In general, such diets generate tiny amounts of

acid each day. With aging, a mild but slowly increasing metabolic

" acidosis " develops, according to the researchers.

Acidosis appears to trigger a muscle-wasting response. So the

researchers looked at links between measures of lean body mass and diets

relatively high in potassium-rich, alkaline-residue producing fruits and

vegetables. Such diets could help neutralize acidosis. Foods can be

considered alkaline or acidic based on the residues they produce in the

body, rather than whether they are alkaline or acidic themselves. For

example, acidic grapefruits are metabolized to alkaline residues.

The researchers conducted a cross-sectional analysis on a subset of

nearly 400 male and female volunteers aged 65 or older who had completed

a three-year osteoporosis intervention trial. The volunteers' physical

activity, height and weight, and percentage of lean body mass were

measured at the start of the study and at three years. Their urinary

potassium was measured at the start of the study, and their dietary data

was collected at 18 months.

Based on regression models, volunteers whose diets were rich in

potassium could expect to have 3.6 more pounds of lean tissue mass than

volunteers with half the higher potassium intake. That almost offsets

the 4.4 pounds of lean tissue that is typically lost in a decade in

healthy men and women aged 65 and above, according to authors. The study

was published in the March issue of the American Journal of Clinical

Nutrition.

Sarcopenia, or loss of muscle mass, can lead to falls due to weakened

leg muscles. The authors encourage future studies that look into the

effects of increasing overall intake of foods that metabolize to

alkaline residues on muscle mass and functionality.

ARS is the U.S. Department of Agriculture's chief scientific research

agency.

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American Journal of Clinical Nutrition, Vol. 87, No. 3, 662-665, March 2008

Alkaline diets favor lean tissue mass in older adults

Background: Maintaining muscle mass while aging is important to prevent

falls and fractures. Metabolic acidosis promotes muscle wasting, and the

net acid load from diets that are rich in net acid–producing protein and

cereal grains relative to their content of net alkali–producing fruit

and vegetables may therefore contribute to a reduction in lean tissue

mass in older adults.

Objective: We aimed to determine whether there was an association of

24-h urinary potassium and an index of fruit and vegetable content of

the diet with the percentage lean body mass (%LBM) or change in %LBM in

older subjects.

Design: Subjects were 384 men and women 65 y old who participated in a

3-y trial comparing calcium and vitamin D with placebo. Potassium was

measured in 24-h urine collections at baseline. The %LBM, defined as

total body nonfat, nonbone tissue weight ÷ weight x 100, was measured by

using dual-energy X-ray absorptiometry at baseline and at 3 y. Physical

activity, height, and weight were assessed at baseline and at 3 y.

Results: At baseline, the mean urinary potassium excretion was 67.0 ±

21.1 mmol/d. Urinary potassium (mmol/d) was significantly positively

associated with %LBM at baseline (? = 0.033, P = 0.006; adjusted for

sex, weight, and nitrogen excretion) but not with 3-y change in %LBM.

Over the 3-y study, %LBM increased by 2.6 ± 3.6%.

Conclusion: Higher intake of foods rich in potassium, such as fruit and

vegetables, may favor the preservation of muscle mass in older men and

women.