By Chris Rosenbloom, PhD, RDN | Wednesday, August 22, 2018
A parent of 16-year-old swimmer asked how much protein is too much? He is concerned about the amount of protein that his son is consuming, based on recommendations that he read in a body-building magazine. The article recommended eating 200 to 250 grams of protein a day to build muscle. In addition, the swimmer wants to add pea protein powder and hemp hearts to his post workout recovery shake, as also suggested by the magazine article.
Let’s break this down. At 160 pounds, this 16-year-old needs a range of protein, depending on his body composition goals, his practice schedule, his energy (calorie) intake, and any additional exercise he does out of the pool (land training, weight training, other aerobic activities, etc.). The low end of the range is 1.2 grams and high end is 2.0 grams per kilogram of body weight. I’ll do the math for you: he needs 87-145 grams of protein a day, ideally spaced out evenly in 4-5 meals each day.
Eating 200 to 250 grams of protein a day would translate to 2.75 to 3.4 grams of protein per kilogram of body weight or much higher than guidelines suggest. So, what is the danger?
While high protein intakes do not cause kidney damage in healthy people, concerns about a high level of protein intake for a swimmer is twofold.
One, a focus on one macronutrient (macro means “big” and big nutrients are carbohydrate, protein, and fat) can crowd out the others. Swimmers need a balance of carbs, protein, and fats. If an athlete focuses on protein, there is likely to be a deficiency of carbs and fat, and that can take a toll on performance and recovery.
Two, a high protein intake can be dehydrating. The body can only handle so much protein at a time, so the excess protein gets stripped of its nitrogen (nitrogen is what makes protein unique and is not found in carbs or fats) and the nitrogen must get excreted by the kidneys in urine. The more nitrogen that shuttled to the kidneys for excretion, more water is needed to remove it. That is why you will always hear the advice to drink a lot of water when you are consuming a high intake of protein.
As for the pea and hemp hearts, these are trendy protein sources and are marketed to plant-based eaters. While the marketing of both is convincing, there is little research to say they are better than the usual protein sources to support muscle growth. In fact, neither contain high levels of the amino acid, leucine, the anabolic trigger that promotes muscle protein synthesis. Stick with a modest intake of protein from real foods and fluids. Dairy foods (milk, yogurt, cottage cheese, and cheese) are good sources of protein, and the amino acid leucine. If a swimmer is eating eggs, beef, chicken, turkey, pork, and fish, protein needs will be met with ease. Add in some lentils and beans, corn, edamame, peanuts, tree nuts, and hummus, and you’ll get not only protein, but other essential nutrients like carbs, vitamins, and minerals.Chris Rosenbloom, PhD, RDN, is a nutrition professor emerita at Georgia State University. She welcomes questions from swimmers, parents, and coaches at firstname.lastname@example.org. Visit her website at chrisrosenbloom.com/.