New Facts About Protein and Endurance


Recently, there’s been a flurry of research on the optimal intake of protein that I have found to be quite interesting.

To save you time, I’ve gleaned three important findings from these studies and present them here.

1) The RDA for protein may be too low.

The current RDA for protein intake in healthy people is set at 0.8 grams of high quality protein per kilogram of body weight (g/kg).

So, if you weigh 150 lbs, which is 68 kg, then you would need 54 grams of protein each day (0.8 x 68 = 54).

But if you are training for an endurance event or wanting to build more muscle mass, you need more protein. Yes, we already knew that – what’s new is that the RDA may need to be even higher than what was previously thought AND it may need to be higher for older individuals.

Before we go any further, let me explain why this is important. Aside from all the cool stuff that protein does for our bodies, which you can read about here, protein plays a huge role in augmenting muscle protein synthesis (MPS), especially as we age and start experiencing sarcopenia (age-related loss of muscle mass and function).

Our muscle mass is regulated by a balance between MPS and muscle protein breakdown (MPB). When MPS exceeds MPB for long and frequent periods of time, muscle growth or “hypertrophy” is the result. Conversely, when there is a net negative protein balance, where MPB exceeds MPS, a reduction in muscle mass occurs, also known as atrophy.

Lest you think that MPS is only important for body-builders, consider that muscle mass, strength, and function are vital to recovery from trauma, critical illness, maintaining normal glucose metabolism, resting energy expenditure, and independent mobility. Thus, protein amount, quality, and daily distribution are important for everyone.

So how much more protein do you need to maintain or build muscle mass? The studies are suggesting 1.2 – 1.4 g/kg/day as the formula for estimating your protein needs of young adults and 1.4 – 1.6 g/kg/day for older adults.

BUT you should NOT consume all or most of that protein in one meal. This brings me to the 2nd important tidbit of helpful info on protein:

2) Distribute your protein requirement into 3-4 meals and 2-3 snacks. Many people eat little or no breakfast, a small lunch, and then a big protein-filled dinner. This is not good, folks.

Protein is made up of amino acids (more on that later) and it appears that when large amounts of protein are consumed in one meal, the excess amino acids are “deaminated” (stripped of the nitrogen component in their molecular structure) and excreted. Buh-bye amino acids!

To prevent this from happening, it’s better to spread your protein out into 3 or 4 meals per day. This is because a “meal protein threshold” needs to be reached every four hours or so, to stimulate MPS and to maintain skeletal muscle mass and function.

How much do you need at each meal? Several researchers have suggested the following formulas:

0.25 g/kg/meal for younger adults (about 20 – 30 grams of protein/meal).

0.40 g/kg/meal for older adults (about 30 – 40 grams of protein/meal.

Sometimes it’s hard to get that much protein in a meal. To make it easier, some researchers are suggesting a pre-sleep protein supplement or meal. The idea is that MPB may occur over night, especially if you don’t eat for more than 12 hours, so to prevent a long period where MPS rates are low, eating a high-protein snack prior to bedtime may do the trick.

Dr. Stuart Phillips at McMaster University explains this concept nicely in this neat little promotional video for a protein product called Ascent (see below). I am NOT promoting this product (or any product) but I thought the video did a good job of explaining why it may be a good idea to have a high protein snack before bed.

You could have Greek yogurt, eggs, or a drink made with any whey, casein, or soy isolate protein powders to get the same result.

3) Proteins with a large amount of the amino acid leucine stimulate MPS more than proteins with a lower amount.

Protein is made up of amino acids, which are referred to as “the building blocks of protein”. One of these building blocks is leucine, a branched-chain amino acid (BCAA). Leucine appears to have a larger effect on muscle-building than others BCAA’s because it triggers a pathway called “mammalian target of rapamycin complex 1” (mTORC1) which is necessary for starting the MPS process.

It appears that the quantity of leucine reaching the bloodstream is important, because the mTORC1 pathway is only initiated when a critical level of leucine is reached, suggesting there might be a “leucine trigger”. However, more is not better because excess amounts of leucine are simply oxidized or deaminated and excreted.

The studies are showing that the ideal amount of leucine is 2.2 – 3.0 grams of leucine per meal.

So, what protein foods are high in leucine?  Whey protein isolate, soy protein isolate, cottage and ricotta cheese, meat, and greek yogurt to name a few. However, there is a calorie cost to some leucine-containing foods.


For example, you would have to eat the following amount of food to get 2.5 grams of leucine:

Whey protein isolate – 1 ounce, 92 calories

Soy protein isolate – 1 ounce, 125 calories

Greek yogurt – 1.1 cups, 143 calories

Eggs – 4.6, 321 calories

Top Round beef – 1.3 servings, 391 calories

Raw peanuts – 5 servings, 876 calories

Whole wheat bread – 12.8 servings, 3462 calories

Should you take leucine supplements? You can but that’s s an expensive way to get leucine. The cheapest and easiest way to get leucine in your diet is via whey or soy protein isolate protein powders.

One more caveat: This only works if you are in “energy balance“, which means you are getting enough total calories each day. If you are dieting, the leucine may be used to replace the muscle that you are probably losing while dieting (more on this in a future article).

Of course, research is ongoing and there is more to learn but for now, your best bet is to consume at least 20 grams of protein at each meal and to include leucine-containing foods as often as possible.

Have questions? Leave them in the comment box and I’ll answer them as soon as I can.

Rock on!


Wolfe RJ, Miller SL. The recommended dietary allowance of protein: a misunderstood concept. JAMA 2008;299:3891-2893.

Wolfe RR. The underappreciated role of muscle in health and disease. Am J Clin Nutr. 2006;84:475-482.

Snijders T et al. Protein ingestion before sleep increases muscle mass and strength gains during prolonged resistance-type exercise training in healthy young men. J Nutr. 2015;145:1178-1184.

Mamerow MM et al. Dietary protein distribution positively influences 24-h muscle protein synthesis in health adults. J Nutr. 2014:144:876-880.

Morton RW et al. Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy. Front Physiol. 2015;6:245.

Phillips SM et al. Protein “requirements” beyond the RDA: implications for optimizing health. Appl Physiol Nutr Metab.2016:41:565-572.

Deutz NE et al. Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clin Nutr. 2014;33:929-936.

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