New Study Suggests More Protein is Better for Building Muscle

image of healthy eating and diet concept - natural rich in protein food on table

Bodybuilders crave their protein shakes and supplements and some drink several a day in hopes of maximizing their muscle gains. It’s debatable how much protein you need to maximize muscle gains, but a new study suggests that more protein is better for muscle gains, especially after the age of 50. So, if you’re aren’t making gains at the rate you think you should take a closer look at your diet, particularly the protein content of what you’re eating.

What the Study Shows

Researchers at McMaster University in Ontario, Canada analyzed the results of 49 well-conducted studies comparing protein intake and muscle gains. In total, the studies included 1,863 people of both sexes. The participants varied in age from young to old. Some were trained weight lifters and others had no prior weight-training experience. When they analyzed the results, they found that diets higher in protein were linked with greater gains in strength and muscle size. In fact, the subjects who consumed higher quantities of protein enjoyed a 25% boost in muscle mass compared to those who ate less protein and a 10% greater boost in strength. That’s substantial!

Yet, we know that the American diet is already relatively high in protein and not everyone needs to eat a high-protein diet. How much protein should the average person who doesn’t weight train consume? Protein recommendations for a sedentary person are 0.8 grams of protein per kilogram of body weight, an amount that the average American easily meets. However, fitness experts argue that people who lift weights and even those who do endurance exercise need more. In this study, gains in muscle strength and size were greater when this amount was doubled to 1.6 grams of protein per kilogram of body weight, a quantity that most of us don’t get without making an effort.

A higher protein diet is particularly beneficial for people over the age of 50. In women after menopause, anabolic resistance becomes a problem. Anabolic resistance is where muscle cells become more resistant to anabolic signals that tell them to grow, including protein. In response to the same amount of protein intake, muscle cells that are anabolic resistant produce less muscle protein. For example, a quantity of protein that would normally stimulate muscle protein synthesis in a 20-year-old has far less impact on a 70-year-old. One way to potentially overcome anabolic resistance and jumpstart muscle protein synthesis is to consume more protein.

What causes anabolic resistance? It’s not clear why anabolic resistance increases with age. One factor may be impaired digestion and breakdown of dietary proteins in the stomach. Stomach acid decreases later in life and this can affect protein digestion. Some research also suggests that the delivery of amino acids to muscle cells is reduced with age. Nevertheless, the amount of protein that was sufficient to build muscle earlier in life isn’t enough later in life.

Another contributing factor to anabolic resistance may be inflammation. As we age, low-grade inflammation increases and this can fuel anabolic resistance. That’s why it’s important to eat more protein and consume whole, unprocessed foods rather than sugary and processed foods made with omega-6-rich oils that fuel inflammation. Some research suggests that consuming a diet high in omega-3s and lower in omega-6’s (abundant in processed foods) may reduce anabolic resistance. The standard, Western diet has a ratio of omega-6 to omega-3 of around 15 to 1 when a healthier ratio would be more like 2 to 1.

Plant versus Animal-Based Protein

Many people picture a high-protein diet as being heavy on meat. That’s not necessarily the case. Although chicken breasts pack 43 grams into a single cup, a cup of tofu has 20 grams of protein. Tofu is one of the few forms of plant protein that’s complete, meaning it contains all the essential amino acids your body need but can’t make on its own. That’s why it’s important to eat a varied diet if you’re plant-based. Whole grain foods lack an essential amino acid that beans and legumes have and vice versa. By choosing diverse sources of plant protein, you can get all the essential amino acids. The biggest drawback to a plant-based diet is you have to eat a lot of food to get enough protein. In addition, absorption of plant-based protein is lower due to the higher fiber content of plant-based foods.

What about protein shakes and supplements? Protein shakes are convenient, but you don’t necessarily need them and you shouldn’t make them the bulk of your diet. Many protein powders are heavily processed and independent testing of some brands has revealed contamination with undesirable ingredients, like heavy metals. Whole foods contain protein in its most natural form. In fact, eggs have the highest biological value of any form of protein, meaning it’s in a form your body can readily use. If you eat a plant-based diet, it might be difficult to consume a high-protein diet since plant foods contain less protein than animal-based foods. A plant protein supplement, like pea protein, that you add to smoothies is an easy way to boost your protein intake.

The Bottom Line

Boosting the protein content of your diet may help you build more strength and muscle size. However, there’s also a limit beyond which a further increase in dietary protein won’t reliably boost muscle growth further. The optimal amount, based on limited research, seems to be around 1.6 grams of protein per kilogram of body weight.

Also, make sure you’re spacing your protein consumption out over the day. Some studies suggest that we can only absorb 20 to 30 grams of protein at a time, so it does no good to consume 50 grams at a sitting. Add high-quality protein to all of your meals and snacks.

Even if your go-to form of exercise is endurance training, you need more protein than a sedentary person to preserve muscle tissue and avoid a catabolic state. Even if you run or do another form of endurance exercise, you still need strength training. So, make sure your workout is balanced.



Exerc Sport Sci Rev. 2013 Jul;41(3):169-73.
ConsumerLab.com “31% of Protein Powders and Drinks Fail Tests by ConsumerLab.com”


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