What's the Deal with Protein?

First, let's get this out of the way now: protein is important. It plays a vital role in the body by providing energy, regulating fluid balance, muscle growth, cell structure, immune function and hormone production.

But protein deficiency is rare in the United States, and there's no doubt that in the last few years, the health and wellness industry has become obsessed with protein.

It's used more and more as a marketing technique, with brands formulating products with added protein and making sure to advertise it on the front of their packaging. If you've ever worked with a personal trainer or spoken with any "nutrition coach" at a gym, the first thing out of their mouth was most likely that you need to eat more protein in order to reach your goals. Fitness social media influencers are paid to push protein supplements to their followers, and it's often accompanied with the advice to eat 1 gram of protein per pound of body weight.

Well, I've got good news for everyone tired of spending extra money on supplements or struggling to get in "enough" protein—you probably don't need as much protein as the industry would like you to believe.

The current protein recommendation for adults is a minimum of 0.8g protein/kg bodyweight. This is an internationally accepted recommendation (1), and is presented as a minimum intake due to the fact that protein recommendations greatly change depending on body composition, age, activity level and goals. Taking this into consideration, if you're an adult with low activity levels (this might include you if you're someone who works a desk job and doesn't have a consistent exercise routine) 0.8-1 g protein/kg body weight is likely enough.

That being said, certain groups may require increased intakes.

Athletic Performance

I want to specify here that when I use the term athlete, I'm referring to someone training on average at least 2-3 hours a day and I would argue this is the most volatile category when it comes to protein requirements. For this reason, many collegiate and professional teams have a sports dietitian on staff.

In their 2016 position paper, the Academy of Nutrition and Dietetics along with the American College of Sports Medicine and Dietitians of Canada stated that athletes should consume anywhere from 1.2-2 g/kg protein per day, spread out as 0.3 g/kg every 3-5 hours.

Athletes in a caloric deficit, period of intense training leading up to a competition or event, or recovering from an injury may require a range of 2-2.3 g/kg per day (2). This is the one case in which consuming the heavily touted 1 g/lb bodyweight may be recommended.

Muscle Growth in Healthy Adults

A 2018 meta-analysis published in the Journal of the International Society of Sports Nutrition supported the Academy's recommendation. Specifically with the goal of muscle growth, this study found a sweet spot of 1.6 g/kg spread across four meals to maximize muscle building in non-dieting resistance-trained individuals. There was no evidence to suggest that consuming protein at a rate higher than this had additional benefits (3, 4).

So if you're someone heading to the gym consistently trying to build muscle, 1.6 g/kg protein per day is a great place to start.

However, it's important to remember that muscle growth will only occur if adequate protein intake is paired with resistance training.

Weight Loss in Resistance-Trained Adults

Weight loss is another circumstance in which higher protein intakes may be suitable for healthy adults.

You've probably heard something like "it keeps you fuller for longer," and the sentiment behind that isn't entirely false. Because protein takes longer to digest than carbohydrates, it prolongs satiety. Protein is also known to have a higher thermic effect than carbohydrates or fats, meaning it requires more energy to digest (5).

A 2015 meta-analysis published in the American Journal of Clinical Nutrition and a 2017 study published in the Obesity Facts concluded that a diet between 1.2-1.6 g/kg protein spread out across the day resulted in improvements in appetite and weight management (6, 7).

Healthy Older Adults

Muscle loss is a common concern in older adults, because it results in decreased mobility and overall body stability.

Two 2018 publishings in Nutrients and Advances in Nutrition found that a protein intake of 1.2 g/kg resulted in better muscle functioning and greater muscle mass retention in adults over age 65 (8, 9). Aiming for this higher protein goal could help improve quality of life and reduce medical risk.

The biggest roadblock in adjusting a diet to meet these recommendations is that older adults tend to experience a decreased appetite due to things such as medications or taste changes. Planning and mindfulness is a useful strategy in order to meet overall calorie and protein needs and prevent undereating in this age group.

Very High Protein Diets

Because I know I'll get questions about it, there have only been a few studies on the effects of short-term very high protein diets.

A 2014 study published in the Journal of the International Society of Sports Nutrition investigated the effect of a very-high protein diet of 4.4g/kg in heavy resistance-trained individuals. They found this diet had no significant effect on body composition compared to the control group consuming 1.8g/kg (10).

A 2015 study from the same lab looked at the difference between 2.3 g/kg and 3.4 g/kg in experienced resistance-trained individuals following a periodized, heavy resistance-training program. The results showed no difference in increase of muscle mass between both groups (11).

They recommended a protein intake of 2 g/kg for experienced resistance-trained individuals.

Vegan Diets

One nuance I think is important to add here, is that the digestibility of plant protein is only about 60-80% depending on the source, whereas animal protein digestibility is > 90% (12). This means that if you're following a vegan diet, you'll need a slightly higher protein intake to account for that difference, with a recommendation of 0.9-1.35 g/kg for the average person and at least 1.8 g/kg for vegan athletes (13).

Caution

And finally, I wouldn't be doing my job as a dietitian if I didn't discuss the potential negative implications of eating a high-protein diet.

Diets high in animal protein may lead to increased cholesterol levels and risk of heart disease. Learning how to incorporate plant proteins into a high-protein diet can help to mitigate this risk.

High-protein diets may also increase your risk of dehydration, due to the extra fluid needed to metabolize protein and clear its byproducts from the kidneys. However, as your body's fluid use increases, your feeling of thirst may not (14). So if you're eating a diet high in protein make sure to be mindful of your fluid intake.

All that being said, at the end of the day you may not need to change your diet, as most Americans already consume somewhere between 1-1.5g protein/kg per day (15). The biggest takeaway I want you to get from this is that protein needs are incredibly unique and specific to you and your goals. At the end of the day, the best way to determine your protein needs is to sit down with a registered dietitian to determine a goal that will best suit you and your lifestyle.

Until next time,

Kristin

Sources

1. Richter M, Baerlocher K, Bauer JM, et al. Revised Reference Values for the Intake of Protein. Ann Nutr Metab. 2019;74(3):242-250. doi:10.1159/000499374

2. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116:501-528. http://dx.doi.org/10.1016/j.jand.2015.12.006.

3. Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. J Int Soc Sports Nutr. 2018;15:10. Published 2018 Feb 27. doi:10.1186/s12970-018-0215-1

4, Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, Helms E, Aragon AA, Devries MC, Banfield L, Krieger JW, Phillips SM. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018 Mar;52(6):376-384. doi: 10.1136/bjsports-2017-097608. Epub 2017 Jul 11. Erratum in: Br J Sports Med. 2020 Oct;54(19):e7. PMID: 28698222; PMCID: PMC5867436.

5.Morales FE Ms, Tinsley GM, Gordon PM. Acute and Long-Term Impact of High-Protein Diets on Endocrine and Metabolic Function, Body Composition, and Exercise-Induced Adaptations. J Am Coll Nutr. 2017 May-Jun;36(4):295-305. doi: 10.1080/07315724.2016.1274691. Epub 2017 Apr 26. PMID: 28443785.

6. Leidy HJ, Clifton PM, Astrup A, Wycherley TP, Westerterp-Plantenga MS, Luscombe-Marsh ND, Woods SC, Mattes RD. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015 Jun;101(6):1320S-1329S. doi: 10.3945/ajcn.114.084038. Epub 2015 Apr 29. PMID: 25926512.

7. Campos-Nonato I, Hernandez L, Barquera S. Effect of a High-Protein Diet versus Standard-Protein Diet on Weight Loss and Biomarkers of Metabolic Syndrome: A Randomized Clinical Trial. Obes Facts. 2017;10(3):238-251. doi:10.1159/000471485

8. Traylor DA, Gorissen SHM, Phillips SM. Perspective: Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance?. Adv Nutr. 2018;9(3):171-182. doi:10.1093/advances/nmy003

9. Coelho-Júnior HJ, Milano-Teixeira L, Rodrigues B, Bacurau R, Marzetti E, Uchida M. Relative Protein Intake and Physical Function in Older Adults: A Systematic Review and Meta-Analysis of Observational Studies. Nutrients. 2018;10(9):1330. Published 2018 Sep 19. doi:10.3390/nu10091330

10. Antonio J, Peacock CA, Ellerbroek A, Fromhoff B, Silver T. 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;11:19. Published 2014 May 12. doi:10.1186/1550-2783-11-19)

11. Antonio J, Ellerbroek A, Silver T, et al. A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women--a follow-up investigation. J Int Soc Sports Nutr. 2015;12:39. Published 2015 Oct 20. doi:10.1186/s12970-015-0100-0)

12.Gertjan Schaafsma, The Protein Digestibility–Corrected Amino Acid Score, The Journal of Nutrition, Volume 130, Issue 7, July 2000, Pages 1865S–1867S, https://doi.org/10.1093/jn/130.7.1865S.

13. Rodriguez NR, DiMarco NM, Langley S. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc 2009;109:509-27.

14. Palmer J. Too much protein can lead to dehydration, researchers find [press release]. University of Connecticut Advance. Published April 29, 2002.

15. Protein intake trends and conformity with the Dietary Reference Intakes in the United States: analysis of the National Health and Nutrition Examination Survey, 2001-2014. Berryman CE, Lieberman HR, Fulgoni VL 3rd, Pasiakos SM

Am J Clin Nutr. 2018 Aug 1; 108(2):405-413.