Can You Get Too Much Protein?

Why does M&F recommend such comparatively high amounts of protein?

A: We have a lot of reasons, but probably the most important one is this: It works to give you the physique you're looking for. "Muscle growth happens when protein synthesis exceeds protein breakdown," Elliott says. "The availability of protein plays an important role in that process, so it follows that increased aminoacid availability—such as what is provided by the intake of dietary protein—will result in a greater anabolic response."
It has been proven that the more protein you eat, the more protein synthesis occurs in your muscles. In a study published in The Journal of Physiology in 2003, researchers found that subjects who had been given an infusion of amino acids experienced a boost in muscle protein synthesis. No surprise, right? The amazing thing was that the rate at which subjects built muscle protein increased as the amount of protein in their bloodstreams increased. Therefore, the more protein you eat, to a degree, the more muscle you'll build—all day long, with or without exercise.
We have other reasons for our recommendations, too. One of them is pretty basic: You're most likely taking supplements (branched-chain amino acids, beta-ecdysterone) that boost protein synthesis, but if you don't have a well of protein for your muscles to draw on, those supplements aren't going to do much. Another reason is because there's evidence that eating protein can keep you lean. For one thing, it's the hardest macronutrient for your body to digest, which means your body has to use more energy (calories) to break it down. Protein also increases the amount of a hunger-blunting peptide called PYY in your bloodstream, meaning you won't be hankering for munchies soon after eating a high-protein meal.
Yet another reason for our protein recommendations is more complicated, but no less rational. In fact, it's all about ratios. In addition to deciding the RDA for nutrients, the FNB recently established what it calls the Acceptable Macronutrient Distribution Range (AMDR) for protein, carbohydrates and fat to tell us what percentage of our calories should come from each. The AMDR for protein is between 10% and 35% of total calories. Now, to support the kind of body you're boasting (or looking to build), you have to put down a lot of calories.
Our advice is generally that a 180-pound guy should eat 18 calories per pound of bodyweight per day, or about 3,240 calories. And that's just to maintain his mass. So let's do the math: Thirty-five percent of 3,240 is 1,134 calories of protein; divide that by 4 (the number of calories in a gram of protein), and you get 284 grams of protein per day. Divide that by our example's bodyweight (180), and you get 1.6 grams of protein per pound of bodyweight per day.
It just goes to show that bodybuilders generally eat within the FNB's acceptable range; it's the FNB that's not familiar with how much food bodybuilders need. Because you consume way more calories (sometimes almost twice the requirement of the average couch-sitter) per day, you have to eat that much more protein. Otherwise, as we discovered by doing more math, you'd be in for an equally fat gut. We plugged in the numbers to see what our 180-pound bodybuilder would be eating if he stuck with the RDA for protein and ate only 0.8 gram of protein per pound of bodyweight per day. Since he'd be eating only 144 grams of protein, he'd have to fill his plate with something else—like, oh, 500 grams of carbs. Needless to say, that's more than his body could use for energy, so all the excess would head straight for his fat stores.

 

Didn't I hear something about kidney damage occurring from too much protein?

A: "The breakdown of amino acids results in the formation of ammonia," Elliott says. "The ammonia is then converted to less harmful urea in the liver and is then passed through the kidneys and excreted in urine." Because it's the job of the kidneys to take away any excess protein that your body's not using, mainstream nutritionists worry that eating excess protein could tax your kidneys. However, several studies have shown that this just isn't the case. One study, presented at the International Society of Sports Nutrition's annual conference in 2005, examined the diets of 77 resistance-trained males and then tested their blood for various markers of kidney health. The subjects ate about 0.8 gram of protein per pound of bodyweight per day, and their kidneys were in perfect health. Another study, conducted at the Free University of Brussels (Belgium), found similar results for people consuming roughly 1.3 grams of protein per pound. There is very strong evidence that athletes taking in more protein are actually using that protein, either to build muscle or to burn as fuel.
 What about my bones? Can't high protein intake make them brittle? A: Some studies have shown that high amounts of protein in the diet can increase the amount of calcium the body excretes, which could potentially lead to fractures and osteoporosis, but those studies mostly involved purified protein and not whole-food protein sources such as meat. "But I drink three protein shakes a day," you say, panicking.
"Isn't that purified protein?" We hear you. But the fact that you also eat whole-food protein sources such as chicken and steak should provide you with enough calcium-protecting phosphorous and other nutrients. That was the finding of one study published in the Journal of Nutrition in 2003. Subjects were fed either a high-meat or a low-meat diet for eight weeks, and researchers found no difference in calcium excretion between the groups.
Still worried? A study at Warsaw Agricultural University (Poland) showed that a high-protein diet in rats actually increased bone mineralization, meaning the rats that ate more protein had stronger bones. Keep in mind that resistance exercise is one of the best ways to keep your bones strong.
So if you ever wonder whether the fit and prim woman at a neighboring table is gaping at your 18-inch arms or at the 18-inch steak on your plate, remember that although we may look like rebels, you can trust us. Everything we write is either backed by extensive scientific research or even more extensive anecdotal evidence. Plus, we practice what we preach, so that we can bring you the most up-to-date, trustworthy advice and you can build the most ferociously muscled body possible. To do that, you have to keep your protein intake on par: Consume at least 1 gram per pound of bodyweight per day of quality lean protein, and drink protein shakes around workout time to make your muscles—and the rest of you—happy.