A diet rich in meat and fish may help older men maintain a higher level of physical, psychological, and social function, according to a recent study WebMD reported.

Japanese researchers found that men who had a high protein diet had a 39 percent decreased chance of experiencing higher-level functional decline than those who consumed little protein.

"Along with other modifiable health behaviors, a diet rich in protein may help older adults maintain their functional capacity," Megumi Tsubota-Utsugi of the National Institute of Health and Nutrition in Japan said in a statement.

For the study, researchers investigate the relationship between protein intake and future decline in higher-level functional capacity in older community-dwelling adults in Japan. They recruited more than 1,000 individuals with an average of 67.4 years who completed food questionnaires at the start of the study and seven years later. Participants were divided into four groups (quartiles) according to their intake levels of total, animal, and plant protein. Tests of higher-level functional capacity included social and intellectual aspects as well as measures related to activities of daily living.

Men benefitted from a high protein diet, but these associations were not seen in women. No consistent association was observed between plant protein intake and future higher-level functional decline in either sex.

Although it shows a relationship between that eating meat and fish and preventing functional decline in men, doesn't actually prove a high protein diet caused the men's health improvements, or that low animal protein intake contributes to early decline.

"It is an observational study that simply shows a relationship between protein and functional decline. It does not prove cause and effect," Lona Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas, told WebMd.