I eat around 2 grams per kilogram a day. Are there are any drawbacks to consuming so much protein? —Damien S., Libertyville, IL
A big imbalance in whatever we eat can lead to problems, Damien, but a high protein intake is considered safe. While some studies suggest that excess protein can lead to kidney failure or brittle bones, a more comprehensive review of 111 studies that appeared in Nutrition & Metabolism in 2005 took a look at protein intake and renal function and found that athletes who consumed more than 2g/kg of protein showed no issues with kidney function.
A high-protein diet can be beneficial, but too much can hurt your muscle-building goals. Enough protein is needed to provide amino acids for building muscle and driving protein synthesis, but any excess protein will be oxidized and used for energy or converted to fat.
If you are consistently eating too much protein, your body will increase the amount of enzymes that burn protein for energy. Also, when bodybuilders eat too much protein, they tend to fall short on other nutrients—including essential fats, fiber, fruit, vegetables, and whole grains. Aim for 30% of calories from protein. This will lend plenty of substrate for protein synthesis and hypertrophy without leading your body to oxidize protein and displace other nutrients.