Ask a body builder, a personal trainer and a registered dietitian how much protein a person needs to eat daily, and you'll likely get three different answers. That's because the amount of protein people need depends, among other things, on their level of physical activity level and their fitness goals.

The recommended dietary allowance (RDA) for protein in adults is 0.8 grams of protein per kilogram of body weight per day (0.8 g/kg/day). It is set by the Institute of Medicine, and though many health organizations and experts say that is not enough to maintain and support muscle growth in older adults, few studies have thoroughly evaluated whether the RDA for protein for older adults is sufficient, particularly for men.

To calculate your RDA for protein, use this simple formula.

“It's amazing how little evidence there is around how much protein we need in our diet, especially the value of high-protein intake,” said corresponding author, Shalender Bhasin, director of the Research Program in Men's Health in the Division of Aging and Metabolism at Brigham and Women's Hospital. “Despite a lack of evidence, experts continue to recommend high-protein intake for older men. We wanted to test this rigorously and determine whether protein intake greater than the recommended dietary allowance is beneficial in increasing muscle mass, strength and wellbeing.”

The study, published in JAMA Internal Medicine, looked at men aged 65 or older with some physical impairments. The men were divided into four groups in a randomized, placebo-controlled, double-blind, parallel group trial.

One group ate a diet that provided the 0.8 gm/kg RDA for protein each day and received an injection of an inactive placebo. Another group’s diet consisted of 1.3 gm/kg of protein each day and a placebo injection. The third group ate the RDA recommended 0.8 g/kg of protein daily and had an injection of testosterone each week. The fourth group ate a diet consisting of 1.3 gm/kg of protein each day and received a weekly injection of testosterone.

The men ate pre-packaged meals that supplied their individualized amounts of protein and calories as well as supplements for six weeks. Eating more protein than the RDA did not affect lean body mass or fat mass, did not improve muscle performance or physical function, and had no effect on energy levels or other measures of well-being in the older men. Protein beyond the RDA also did not increase muscle building among those who had testosterone injections.

For many older adults who have poor appetites, chronic diseases or are suffering from depression, eating enough to meet the RDA for protein is a struggle. “Our data highlight the need for re-evaluation of the protein recommended daily allowance in older adults, especially those with frailty and chronic disease,” the authors write.

Calculate Your Protein Needs
To calculate your RDA for protein, use this simple formula: Divide your weight in pounds by 2.2 to convert it to kilograms. Multiply that number by 0.8. The result is your recommended daily allowance for protein in grams. The RDA applies only to healthy individuals. Disease states could increase or decrease the amount of protein you should eat each day.