“Energy and persistence conquer all things.”

― Benjamin Franklin

Protein

Protein is a macronutrient with four calories per gram. The body breaks it down into a pool of amino acids for many uses such as repairing and building muscle tissue.

How Much Protein to Eat

According to the Institute of Medicine,[1] your protein consumption is 10 to 35 percent of your daily calories.

But since your body composition is unique, a more refined number should be used.

About 0.6 to 0.8 grams of protein per pound of body weight (1.3 to 1.8 grams of protein per kilogram of body weight) is adequate for promoting maximal protein synthesis according to McMaster University.^[2] However, more might be required in cases of strictly losing fat while preserving muscle mass and frequent high-intensity training.

As high as 1 to 1.4 grams per pound of fat-free mass (skeletal muscle, bone, water, etc.) for maintaining muscle while losing fat according to other research.^[3] Depending on your goal (cutting, bulking, or maintaining), the protein intake, as well as carbohydrate and dietary fats, will vary to maximize progress.

The Best Sources of Protein

The two main sources of protein come from whole foods and supplements.

Because the body doesn’t metabolize all proteins the same way, some proteins are better than others. For example, the body digests egg protein much slower than steak although the body uses it more efficiently.^[4]

The Protein Digestibility Corrected Amino Acid Score (PDCAAS)^[5] ranks proteins with a score of 0 to 1, from worst to the best possible source.

To receive the benefits of quick digestion and supply of essential amino acids, the best sources based on the chart above are meat, eggs, and dairy products.

A close second is plant sources like nuts, legumes, and high-protein vegetables such as broccoli, peas, and spinach.

Although consuming protein from meat sources is more effective than vegetarian products for building muscle^[6] because some vegetables have lower certain amino acids such as leucine, you can still build a strong body with a plant-based protein diet.

Although eating protein itself doesn’t increase testosterone, it can lead to having higher quality strength training workouts, which in effect can raise your level of testosterone. In a study^[7], people who consumed protein from meat (eggs and dairy) showed significant muscle growth and fat loss than those who didn’t despite experiencing equal strength.

How You Absorb Protein

Protein absorption is the duration that the body requires to absorb the amino acids into the bloodstream.

After digestion by stomach acid and enzymes, the amino acids are transported into the bloodstream and to other parts of the body by intestine cells.

Not all protein is equal since the body absorbs different proteins at different rates.

Because protein causes the stomach to produce cholecystokinin (CCK), a hormone that inhibits gastric emptying and decreases gastric acid secretion, the body requires a longer time to absorb protein compared to that carbohydrates and dietary fat.

Not only can protein help in muscle growth and repair, but any extra can also be temporarily stored in muscles for up to 24 hours for future use.

Furthermore, the body can break down protein into fuels for the brain and other cells.

How Often You Should Eat Protein

Protein consumption amount per meal isn’t as important as consuming the adequate amount per day although eating larger quantities of protein in fewer meals is inferior to consuming smaller amounts of protein in more frequent meals.

If you’re looking to maximize muscle growth, three servings of 30 to 40 grams of protein per day are sufficient.

My usual protein intake is 30 grams of protein before and after a workout. At dinner, I’ll eat another 30 to 40 grams of protein.

Protein Supplements

The main protein supplements are:

• Whey

• Casein

• Egg

• Soy

• Other plant-based protein powders

Let’s discuss each in order. Whey is a dairy product from cheese production. 

Because of its relatively inexpensive price, suitable amino acid profile for building muscle, and delicious taste, it’s the most popular type of protein supplement.

Leucine is the essential amino acid and key compound for protein synthesis^[8] found in whey. Because of its quick digestibility, whey is an excellent choice for post-workouts to stimulate muscle growth.

As for casein, it’s a protein found in milk. Because it digests slower than whey, casein is a great choice for building muscle and muscle recovery.

Now for egg protein, the body digests it slower than casein. 

Therefore it’s also another great choice for muscle growth. But for soy protein, there is conflicting research. 

Isoflavone, an estrogen-like molecule found in soy, can cause men’s estrogen levels to rise.^[9] Daidzein (isoflavone in soy) requires a certain intestinal bacteria for its conversion into an estrogen-like hormone called equol.

Because 94 percent of the soybeans grown in the United States are genetically modified,^[10] it’s best to avoid genetically modified foods until more research has been done to show their long-term health effects on humans.

Rice, hemp, and pea are other plant-based protein options besides soy.

However, the best option is pea because it has a PDCAAS value of 0.82, high leucine content, and a comparable amino acid profile to that of whey.

Both rice and hemp proteins aren’t appealing with PDCAAS values of 0.50 and 0.48, respectively.

Despite the numerous healthy micronutrients such as omega-3 and omega-6 fatty acids, hemp contains only 30 to 50 percent protein by weight and isn’t easily digested like rice or pea protein.    

Closing Thoughts

Protein is essential for building and maintaining muscle.

Regardless of your fitness goal, use the protein stated in this article as mere guidelines to maximize your progress.

Consuming protein from nutrient-dense foods is the best option, but protein supplements are convenient because they contain a minuscule amount of carbohydrates and dietary fat so you can reach your daily target protein needs without exceeding your calorie intake.

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Footnote References:

^[1]Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Washington, D.C.: National Academies Press, 2005.

^[2]Stuart  M. Phillips and Luc J. C. Van Loon, “Dietary Protein for Athletes: From Requirements to Optimum Adaptation,” Journal of Sports Sciences 29, no. S1 (2011): S29-S38. doi:10.1080/02640414.2011.619204.

^[3]Eric r. Helms, Caryn Zinn, David S. Rowlands, and Scott R. Brown, “A Systematic Review of Dietary Protein during Caloric Restriction in Resistance Trained Lean Athletes: A Case for Higher Intakes,” International Journal of Sport Nutrition and Exercise Metabolism 24, no. 2 (2014):127-38. doi: 10.1123/ijsnem.2013-0054.

^[4]Bilsborough, Shane, and Neil Mann. “A review of issues of dietary protein intake in humans.” International Journal of Sport Nutrition and Exercise Metabolism 16, no. 2 (2006): 129; Norton, Layne E., Gabriel J. Wilson, Donald K. Layman, Christopher J. Moulton, and Peter J. Garlick. “Leucine Content of Dietary Proteins is a Determinant of Postprandial Skeletal Muscle Protein Synthesis In Adult Rats.” Nutr Metab 9, no. 1 (2012): 67.

^[5]“Protein Digestibility Corrected Amino Acid Score.” Wikipedia. Wikimedia Foundation, n.d.

^[6]Anne Raben, Bente Kiens, Erik A. Richter, Lone B. Rasmussen, Birgit Svenstrup, Snezana Micic, and Paul Bennett, “Serum Sex Hormones and Endurance Performance after a Lacto-Ovo Vegetarian and a Mixed Diet,” Medicine and Science in Sports and Exercise 24, no. 11 (1992): 1290-97; Mylène Aubertin-Leuheudre and Herman Adlercreutz, “Relationship between Animal Protein Intake and Muscle Mass Index in Healthy Women,” British Journal of Nutrition 102, no. 12 (2009): 1803-10. Doi: 10.1017/S0007114509991310.

^[7]Wayne, W. Campbell, Marvin L. Barton Jr., Deanna Cyr-Campbell, Stephanie L. Davey, John L. Beard, Gianni Parise, and William J. Evans, “Effects of an Omnivorous Diet Compared with a Lactoovovegetarian Diet on Resistance-Training-Induced Changes in Body Composition and Skeletal Muscle in Older Men,” American Journal of Clinical Nutrition 70, no. 6 (1999): 1032-39.

^[8]Layne E. Norton, Gabriel J. Wilson, Donald K. Layman, Christopher J. Moulton, and Peter J. Garlick, “Leucine Content of Dietary Proteins Is a Determinant of Postprandial Skeletal Muscle Protein Synthesis in Adult Rats,” Nutrition and Metabolism 9, no. 1 (2012):67. Doi: 10.11867/1743-7075-9-67; Satoshi Fujita, Hans C. Dreyer, Micah J. Drummond, Erin L. Glynn, Jerson G. Cadenas, Fumiaki Yoshizawa, Elena Volpi, and Blake B. Rasmussen, “Nutrient Signalling in the Regulation of Human Muscle Protein Synthesis,” Journal of Physiology 582, pt. 2 (2007): 813-23. Doi: 10.1113/jphysiol.2007.134593.

^[9]Bachua Liu, Liquiang Qin, Aiping Liu, Yuhui Shi, and Peiyu Wang, “Equol-Producing Phenotype and in Relation to Serum Sex Hormones Among Healthy Adults in Beijing,” [In Chinese], Wei Sheng Yan Jiu 40, no. 6 (2011): 727-31.

^[10]Adoption of Genetically Engineered Crops in the U.S.,” United States Department of Agriculture, last updated July 14, 2016, http://www.ers.usda.gov/data-products/adoption-of-genetically-engineered-crops-in-the-us. aspx#. VEkhhkPldWWQ.