Can You Eat Too Much Protein?

Can you eat too much protein? An interesting question that suggests a second question: When does “too much” actually occur? Is three grams per pound of bodyweight a day too much to consume? What about two grams?

What’s interesting is that the scientific literature tends to define “high-protein” diets relative to the RDA, which is a paltry 0.8 grams of protein daily per kilogram of bodyweight. Now, if your standard is that ungodly low, then, heck, anything would seem high. It would be like measuring your height against a group of Pygmies and saying that you’re tall.

A recent study looked at whether a high-protein diet affected the immune system in response to a large volume of high-intensity exercise. Eight well-trained cyclists performed two separate weeks of high-intensity training while consuming either a high-protein diet of three grams per kilogram of bodyweight or an energy-and-carbohydrate-matched control diet that contained half the protein. Three grams per kilogram is equal to 1.4 grams per pound of bodyweight. So it’s 40 percent higher than the typical recommendation of one gram per pound daily.

In this study the high-intensity-training weeks were preceded by a week of normal-intensity training under the control diet. The researchers discovered that high-intensity training performed during a high-protein diet was associated with fewer symptoms of upper-respiratory-tract infections, or URTI, than high-intensity training performed during a normal diet. So a high-protein diet may reduce the incidence of URTI in athletes by preventing training-induced impairments in immune-surveillance.¹

In another study, scientists determined the effects of a prescribed weight-loss diet with 0.8 vs. 1.4 grams of protein per kilogram of bodyweight daily in overweight and obese men.² Isn’t it odd that they described 1.4 grams per kilogram as high? That’s equal to 0.64 grams per pound daily. To me, that ain’t high. That’s the Pygmy comparison. In any event, let’s see what happened.

The 12-week diets were 750 calories less than the subjects’ daily needs, with the main difference being protein content. Both groups lost comparable bodyweight and fat; however, the high-protein group lost less lean body mass than the normal-protein group. The researchers concluded that “energy restriction effectively improves multiple clinical indicators of cardiovascular health and glucose control, and consumption of a higher-protein diet and accomplishing weight loss when overweight vs. obese help men preserve lean body mass over a short period of time.” So, when it doubt, just eat more protein.

—Jose Antonio, Ph.D.

 

Editor’s note: Jose Antonio, Ph.D., is an assistant professor at Nova Southeastern University in sunny South Florida.

 

¹ Witard, O.C., et al. (2013). High dietary protein restores overreaching induced impairments in leukocyte trafficking and reduces the incidence of upper respiratory tract infection in elite cyclists. Brain Behav Immun. Published online October 10.

² Tang, M., et al. (2013). Normal vs. high-protein weight loss diets in men: effects on body composition and indices of metabolic syndrome. Obesity (Silver Spring). 21:E204-210.