In the past century, the leading causes of death have shifted from infectious diseases, such as pneumonia and tuberculosis, to chronic diseases such as cardiovascular disease and cancer – and research suggests that poor diet may a culprit.

The findings are particularly relevant for people with rheumatoid arthritis, or RA, who already have a higher risk of heart disease than the general population.

But researchers report that it's never too late to do something about it: Eating a healthy diet, even if you start at age 70, can add years to your life, according to a study in the January 2011 issue of the Journal of the American Dietetic Association.

The Deadliest Diets

Researchers at the University of Maryland in College Park asked more than 2,500 people, ages 70 to 79, detailed questions about their typical diet. Six major dietary categories were identified, based on participants' predominant food choices.

Those who ate a diet rich in high-fat dairy products like ice cream and cheese were 40 percent more likely to die over the study’s 10-year period than those who opted for a healthful diet filled with vegetables, low-fat dairy products and whole grains.

Those who favored sweets and deserts were 37 percent more likely to die than those who consumed a healthy diet, says lead author Amy Anderson, PhD, a postdoctoral fellow in the department of nutrition and food science at the University of Maryland in College Park.

The analyses took into account other factors that affect mortality including sex, age, race, education, physical activity, smoking and total caloric intake.

"Our study supports previous findings suggesting that eating a healthy diet is associated with better quality of life and longer survival – no matter what your age," Anderson says.

Eat Right for Arthritis

Quality of life can especially improve for patients with different forms of arthritis, adds Joel M. Kremer, MD, director of research at the center for rheumatology at Albany Medical College in New York.

“A healthy diet typically means fewer calories. And simply taking in fewer calories will turn down the gas on inflammation, resulting in fewer flare-ups," he says.

Eating well to live longer has the added bonus of helping people shed pounds and avoid obesity, Kremer says.

"Obesity is associated with premature osteoarthritis of the knees and hips. And people with RA who have a higher BMI tend to respond less well to their medications and to have worse disease," he says.

Also, obesity can raise the levels of uric acid in the blood and may increase the risk of gout. Recent research suggests that the reverse is also true – losing weight may lower uric acid levels and reduce gout risk, Kremer adds.

Turning poor dietary habits around isn't easy, the experts acknowledge. "But even small changes" – substituting whole grain toast for a croissant in the morning, for example – "can have a huge impact on your health and longevity," says study co-author Nadine Sahyoun, PhD, a registered dietitian and associate professor of nutrition and food science at the University of Maryland.