Protein is one of the most popular nutrition topics among fitness enthusiasts. As a result, there is an abundance of information about protein available online; however, much of this information is conflicting, which can lead to confusion and a number of questions.
Here are some science-based answers to a few of the most common questions about protein.
QUESTION #1: How much protein should I eat to gain muscle?
The recommended daily allowance (RDA) for protein is roughly 0.36g protein / lb bodyweight / day. This number represents the minimum amount of protein needed for a sedentary healthy individual to prevent deficiencies. However, many in the fitness industry are interested in maximizing muscle growth rather than preventing deficiencies.
Numerous researchers looking at protein intake for muscle growth have found that increasing protein intakes above the RDA (as high as 0.8-0.9 g protein / lb bodyweight / day) have been shown to result in further increases in muscle mass (1).
ANSWER: Those interested in maximizing muscle growth may benefit from increasing protein intake to 0.8-1.0 g protein / lb bodyweight /day. If an individual has a large amount of body fat, base this number off of estimated lean body mass rather than body weight.
QUESTION #2: How much protein should I eat while dieting?
Although 0.8-1.0g protein / lb bodyweight / day appears to be sufficient to maximize muscle growth, when an individual is in a caloric deficit protein needs may be higher to prevent muscle loss. Numerous studies have observed less muscle loss with dieting in individuals consuming a protein intake of above 1g protein / lb bodyweight / day (2-5). As a result, a recent meta-analysis on protein intakes in dieting athletes recommended a protein intake of 1 – 1.4 g protein / lb lean body mass / day to maximize muscle retention (2).
ANSWER: An increased protein intake while dieting may help prevent muscle loss, especially in those who are very lean and training hard. Consume 1 to 1.4g protein /lb lean body mass/day to maximize muscle retention while dieting.
QUESTION #3: Can I make more progress if I eat more protein?
Intakes above the RDA have been shown to be beneficial for muscle growth during lean gaining phases and muscle retention while dieting. As a result, it is common for individuals to think that if more protein is beneficial then a lot more protein will be even better. However, there is not strong evidence that protein intakes above those listed above results in more muscle growth.
In fact, too much protein may limit the number of carbohydrates and fat you can fit in to your caloric allotment and potentially slow progress. Additionally, excess protein is either broken down for energy or can be stored as body fat. While it is true that it takes more energy to break down and store protein than carbohydrate or fat, too much protein in a caloric surplus can be converted to body fat.
ANSWER: There is no evidence that extremely high protein intakes will result in significantly more muscle growth. If anything, extremely high protein intakes may either result in body fat gain and/or less progress if it results in insufficient carbohydrate/fat intake.
QUESTION #4: Are high-protein diets harmful to the liver or kidneys?
Safety of high-protein diets is a common concern. However, in a recent study where healthy young men consumed 2g protein/ lb bodyweight/ day (5.5 times the RDA), no change in markers of kidney or liver function after 8 weeks (6).
Similarly, a study from earlier this year observed no difference in liver or kidney function between those consuming 1.5 g protein / lb bodyweight / day or their normal protein intake. Interestingly, since the population studied were young healthy male weightlifters, normal protein intake was slightly over 1g protein / lb bodyweight / day providing evidence that long-term consumption of protein intakes at or slightly above 1g protein / lb bodyweight / day is not detrimental to kidney or liver health (7).
ANSWER: There is no evidence that regular consumption of 1g protein / lb bodyweight / day in healthy young men is detrimental to liver or kidney health. Furthermore, short term (2 months) consumption of intakes up to 2g protein / lb bodyweight / day have not been shown to adversely affect liver or kidney health.
QUESTION #5: Is a high protein diet detrimental to bone health?
An additional health concern often voiced about high protein diets is that they may be detrimental to bone health. However, bone is made up in part by a protein matrix suggesting that protein may be beneficial for bone health. As a result, a recent review of literature on protein and bone health concluded that high protein diets are not detrimental for bone health and in fact, low-protein diets may be detrimental to bone health (8).
ANSWER: There is no evidence that high protein diets are detrimental to bone health in healthy individuals.
QUESTION #6: Is there a maximum amount of protein that I can eat per meal?
Many individuals wonder how much protein the body can handle at once. However, protein digestion and absorption is highly efficient and not a limiting factor. Once protein is absorbed, it can be used to build and repair muscle through the process of skeletal muscle protein synthesis. Skeletal muscle protein synthesis has been shown to be maximized after a meal containing around 20g protein in young men (9). However, meals containing up to 70g protein have been shown to further reduce skeletal muscle protein degradation (the rate at which muscle is broken down) so excess protein consumed in a meal is not wasted (10).
ANSWER: There is not a maximum amount of protein that can be consumed per meal.
QUESTION #7: Do I need to eat protein every 2-3 hours?
In the fitness world, it is common for individuals to eat a meal containing protein every 2-3 hours in an attempt to maximize muscle growth. However, there is no evidence of an effect of meal frequency on muscle mass (11-15). In addition, uneven protein distributions (a majority of protein consumed in one meal daily) has been shown to produce similar effects on skeletal muscle protein turnover (16) and lean mass retention during weight loss (17) as balanced distributions when calorie and macronutrient intake matched. These results suggest that consuming an adequate total intake of protein over the course of the day is more important than the distribution of protein throughout the day.
ANSWER: You do not need to eat protein every 2-3 hours to maximize muscle growth. Focus on consumption of adequate protein daily rather than the distribution of protein throughout the day.
QUESTION #8: Do I need to take a protein shake immediately post-exercise?
Many individuals slam a protein shake immediately post-exercise to take advantage of the post-exercise “anabolic window.” However, recent evidence suggests that the anabolic window is significantly longer than previously thought (18). Moreover, a recent meta-analysis of studies looking at protein intake during the first hour post-exercise and muscle growth observed no effect of protein within the first hour after a workout when protein intake was matched throughout the day (19).
ANSWER: Consumption of protein immediately post-workout does not appear to be necessary to maximize muscle growth. Whether you choose to have a shake post-workout will not affect long-term progress so long as adequate protein is consumed throughout the day.
QUESTION # 9: Are nuts a good source of protein?
People looking for a high-protein snack will commonly consume a handful of nuts. However, nuts are not all that high in protein, containing only 6g per ounce. Nuts are also an incomplete protein source, meaning they are deficient in some essential amino acids. Moreover, nuts are calorically dense (approximately 170 calories/oz) which means they may not be the best source of protein for those with caloric restrictions, since you would have to consume 500-600 calories of nuts to get 20g of protein (and incomplete protein at that).
However, it should be noted that nuts are a good source of mono- and polyunsaturated fat when eaten within the confines of an appropriate caloric intake; therefore, they should not be purposefully eliminated from the diet for those without a medical reason to do so.
ANSWER: : Nuts are a good source of mono- and polyunsaturated fat; however, they should not be considered a good source of protein.
QUESTION #10: Should I get protein from whole food or supplements?
Protein shakes and bars are a convenient way to get complete sources of protein when schedules get busy and can be a tasty alternative to other complete (primarily animal) sources of protein. Assuming calorie and macronutrient intake is matched, there will be no difference in progress between consumption of protein from whole food or supplements.
ANSWER: Consume food and/or supplements based upon your preference and schedule to meet your daily protein needs.
References:
1. Phillips, S.M. and L.J. Van Loon, Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci, 2011. 29 Suppl 1: p. S29-38.
2. Helms, E.R., et al., A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab, 2014. 24(2): p. 127-38.
3. Mettler, S., N. Mitchell, and K.D. Tipton, Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc, 2010. 42(2): p. 326-37.
4. Walberg, J.L., et al., Macronutrient content of a hypoenergy diet affects nitrogen retention and muscle function in weight lifters. Int J Sports Med, 1988. 9(4): p. 261-6.
5. Longland, T.M., et al., Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr, 2016.
6. Antonio, J., et al., The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr, 2014. 11: p. 19.
7. Antonio, J., et al., The effects of a high protein diet on indices of health and body composition – a crossover trial in resistance-trained men. Journal of the International Socieity of Sports Nutrition, 2016. 13: p. 3.
8. Kerstetter, J.E., A.M. Kenny, and K.L. Insogna, Dietary protein and skeletal health: a review of recent human research. Curr Opin Lipidol, 2011. 22(1): p. 16-20.
9. Witard, O.C., et al., Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am J Clin Nutr, 2014. 99(1): p. 86-95.
10. Kim, I.Y., et al., The anabolic response to a meal containing different amounts of protein is not limited by the maximal stimulation of protein synthesis in healthy young adults. Am J Physiol Endocrinol Metab, 2015: p. ajpendo 00365 2015.
11. Cameron, J.D., M.J. Cyr, and E. Doucet, Increased meal frequency does not promote greater weight loss in subjects who were prescribed an 8-week equi-energetic energy-restricted diet. Br J Nutr, 2010. 103(8): p. 1098-101.
12. Stote, K.S., et al., A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr, 2007. 85(4): p. 981-8.
13. Soeters, M.R., et al., Intermittent fasting does not affect whole-body glucose, lipid, or protein metabolism. Am J Clin Nutr, 2009. 90(5): p. 1244-51.
14. Arnal, M.A., et al., Protein feeding pattern does not affect protein retention in young women. J Nutr, 2000. 130(7): p. 1700-4.
15. Arnal, M.A., et al., Protein pulse feeding improves protein retention in elderly women. Am J Clin Nutr, 1999. 69(6): p. 1202-8.
16. Kim, I.Y., et al., Quantity of dietary protein intake, but not pattern of intake, affects net protein balance primarily through differences in protein synthesis in older adults. Am J Physiol Endocrinol Metab, 2015. 308(1): p. E21-8.
17. Adechian, S., et al., Protein feeding pattern, casein feeding or milk soluble protein feeding did not change the evolution of body composition during a short-term weight loss program. Am J Physiol Endocrinol Metab, 2012.
18. Burd, N.A., et al., Enhanced amino acid sensitivity of myofibrillar protein synthesis persists for up to 24 h after resistance exercise in young men. J Nutr, 2011. 141(4): p. 568-73.
19. Schoenfeld, B.J., A.A. Aragon, and J.W. Krieger, The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. J Int Soc Sports Nutr, 2013. 10(1): p. 53.
