How Much Protein is Best Depends on Different People’s Needs

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Introduction

I often hear the question, “how much protein is best?” but that depends for whom. Different people have different protein needs. A healthy man or woman seeking to build muscle has a different protein need than an older adult wanting to reduce the risk of sarcopenia (muscle loss) or someone simply wanting to prevent deficiency. The amount of protein someone needs depends on many factors, including whether a person is growing, pregnant or lactating (breastfeeding), or has been sick or just had surgery.

Protein needs are calculated as grams of protein per kilogram of body weight of the person, and not as a percentage of daily calories (energy). As explained below, 40% of calories as protein may be safe for one person and be in excess for someone else. For this reason, protein must be calculated as grams of protein per kilogram of body weight.

Basic Needs – The Recommended Daily Allowance (RDA)

The Recommended Daily Allowance (RDA) for any nutrient is the average daily dietary intake level that is sufficient to meet the needs of 97-98% of healthy people. It is important to keep in mind that the RDA is not the optimal requirement, but the absolute minimum to prevent deficiency.

The RDA for protein for healthy adults is calculated at 0.8 g protein/kg of body weight [1]. A sedentary 70 kg / 154 pound man needs a minimum of 56 g of protein, and a sedentary 60 kg / 132 pound woman needs a minimum of 48 g of protein per day.

Protein Needs for Active Healthy Adults

For those who are physically active, the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine [2] recommend a protein intake of 1.2—2.0 g protein/kg per day to optimize recovery from training, and to promote the growth and maintenance of lean body mass.

Protein Needs for Older Adults

There have been several position statements issued by those who work with an aging population, indicating that protein intake between 1.0 and 1.5 g protein/kg per day may best meet the needs of adults during aging [3,4].

[UPDATE (August 15, 2023): Protein needs for older adults are now established at above 90g per day, with the optimal amount of 30g highly bioavailable protein over each of 3 meals, along with sufficient amounts of the amino acid leucine, which is needed to trigger muscle protein synthesis. This updated article explains.]

Range of Safe Intake

As I wrote about in an earlier article, according to Dr. Donald Layman, PhD, the highest end of the range of safe intake of protein is 2.5 g protein/ kg per day.

Someone eating on occasion above their safe range is a different scenario than someone eating above or at the very high end of that range regularly. The body has a flexible capacity to tolerate higher protein intake on occasion, but regularly eating too much protein can result in protein toxicity.

Maximum Amount of Protein the Body Can Safely Process

When protein is eaten, the body needs to get rid of the ammonia that results, and this is done by turning the ammonia into urea and excreting it in the urine. Tracer studies suggest that the disposal rate of ammonia is flexible, enabling us to survive high-protein days interspersed with low-protein days.

The effective rate limit for maximal disposal of urea through urine is 3.21 g of protein/kg lean body mass [5]. If someone were to eat above that amount of protein for too long, they would fill their reservoirs and be at risk of ammonia intoxication. This calculation requires knowing a person’s lean body mass (LBM).

Lean body mass (LBM)can be estimated using relative fat mass (RFM), as described in this article. Once we know LBM, we use the equation to determine the maximum ongoing protein intake.

Final Thoughts…

To know if a diet has adequate protein, one needs to ask, “Adequate for whom?” Diets should at least meet the bare minimum requirements of the RDA, then be adjusted for an older adult, or to sustain someone who is physically active, while making sure the amount of protein is within the safe upper limit for urea disposal. or for an older adult.

More Info?

I have a dedicated package that ensures that older adults eat sufficient amounts of highly bioavailable protein to preserve both muscle mass and bone mass. You can view the Healthy Aging Package here, and learn about me here.

To your good health!

Joy

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References

  1. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. The National Academies Press. 2005. [https://doi.org/10.17226/10490]
  2. Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016 Mar;48(3):543-68. [https://pubmed.ncbi.nlm.nih.gov/26891166/]
  3. Fielding RA, Vellas B, Evans WJ, et al. Sarcopenia: an undiagnosed condition in older adults. Current consensus definition: prevalence, etiology, and consequences. J Am Med Dir Assoc. 2011 May;12(4):249-56. [https://pubmed.ncbi.nlm.nih.gov/21527165/]
  4. Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013 Aug;14(8):542-59. [https://pubmed.ncbi.nlm.nih.gov/23867520/]
  5. Rudman D, DiFulco TJ, Galambos JT, et al. Maximal rates of excretion and synthesis of urea in normal and cirrhotic subjects. J Clin Invest. 1973 Sep;52(9):2241-9. [https://pmc.ncbi.nlm.nih.gov/articles/PMC302486/]
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