Nutritional Implications of Rheumatoid Arthritis

For some people, the benefits of eating a healthy diet are hard to detect on a daily basis. But for others—such as those with rheumatoid arthritis—the effects are often much more palpable.

Rheumatoid arthritis, or RA, is a chronic inflammatory disease with three diet-associated aspects. One is elevated resting energy expenditure. Another is elevated whole-body protein catabolism—a destructive form of muscle metabolism that translates to muscle wasting. And yet another is low body cell mass, which leads to increased fat mass.

Nutritionist Susan B. Roberts, rheumatologist Ronenn Roubenoff, and colleagues have conducted a study that solves the puzzle as to whether folks with RA should increase their caloric intake to make up for their increased resting energy expenditure. Roberts is director of the Energy Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts. Roubenoff has a visiting appointment with the center.

People with RA tend to be less active than people without—the stiffness and swelling caused by inflammation naturally prompt them to pursue less physical, more sedentary lifestyles. Such habits lead in turn to overall gains in fat mass. The combination of high fat mass and low muscle mass contributes to an increased risk of disability.

Researchers at the center had previously shown that those who develop RA also develop an increased metabolic rate; they simply burn more calories while at rest. But they did not know what effect the elevated resting energy expenditure has on daily total energy expenditure and thus on dietary energy requirements.

Twenty healthy women and 20 women with RA, all of similar weight and size, were studied. Their total energy expenditure and their energy expended during rest and during exercise were measured or estimated. These three measures make up the major components of the energy balance equation.

The researchers found that in the women with RA, low energy expenditure from physical activity was directly linked to lower total energy expenditure. "Even though their basal metabolism is revved up, people with rheumatoid arthritis tend to be less active than people without—which reduces their caloric needs," says Roberts. This finding helped solve the puzzle of whether women with RA need to eat more to make up for the fact that they burn more calories while at rest. They don't.

The researchers concluded that those with RA should consume nutrient-rich diets and incorporate physical activity throughout the day to boost their total energy expenditure. "Such a regimen will help them improve their physical function and quality of life and maintain a healthy weight," says Roubenoff.

The study was published in the American Journal of Clinical Nutrition.—By Rosalie Marion Bliss, Agricultural Research Service Information Staff.

To reach scientists mentioned in this article, contact Rosalie Bliss, USDA-ARS Information Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-5129; phone (301) 504-4318, fax (301) 504-1641.

"Nutritional Implications of Rheumatoid Arthritis" was published in the July 2004 issue of Agricultural Research magazine.