How Much Protein Do You Need to Fuel Your Body?

U.S. Soy Staff

If you’re a dietitian or nutritionist, you’re already familiar with the importance of protein. "Protein" comes from the Greek word “proteios,” which means of the first rank or position, and primary importance. The word was originally coined in 1838 and was chosen to represent the fundamental nature of protein’s role in human nutrition.

However, the nutritional importance of protein is also due to its constituent amino acids—the fundamental molecule that serves as the building block for protein. As a result, both the quality and quantity of protein are important for a healthy lifestyle. Learn why your clients depend on dietary protein and how to help them meet their daily requirements with high-quality soy foods. 

How Much Protein Do You Need to Fuel Your Body?

Why Dietary Protein Matters
Dietary protein is an essential component of a healthy diet and supports the following:2,3 
  • Growth and development (especially in children, teens, and pregnant or breastfeeding women)
  • Repair and maintenance of tissues
  • Supporting overall health and metabolic function
  • Maintaining muscle mass

How Much Protein Do Your Clients Need?

When determining protein requirements, nutrition experts use two key benchmarks from the Dietary Reference Intakes (DRIs):

  • EAR (Estimated Average Requirement): The average daily amount of protein estimated to meet the needs of half the healthy people in a specific age and gender group.
  • RDA (Recommended Dietary Allowance): The amount that meets the needs of nearly all (97–98%) healthy individuals in that group.

However, there are challenges in measuring protein requirements:

  • These numbers are minimums—not the maximum amount your clients should eat.
  • Protein RDAs are based on research in young adults, and other life stage recommendations are calculated using mathematical models.
  • Your clients’ protein intake needs might be higher if they’re active, pregnant, breastfeeding, or recovering from illness.

Understanding Protein Intake Requirements

Recommendations for young adults are approximately 0.66 g/kg/d and 0.8 g/kg/d as the EAR and RDA (Table 1). These values are based on available nitrogen balance studies.4 The nitrogen balance method determines how well an individual utilizes protein by measuring their nitrogen intake and excretion. This has been the traditional method to determine protein requirements. However, there are several shortcomings of the nitrogen balance method, which could lead to scientists underestimating daily protein requirements.4,5


Daily Protein Intake Requirements and the IAAO Method

Unlike the nitrogen balance method, the indicator amino acid oxidation (IAAO) method is a minimally invasive technique that determines protein requirements based on the metabolic availability of amino acids.5,6 It’s a newer method of measuring protein requirements that may be better at assessing protein and essential amino acid needs in different populations.7 

Using the IAAO method described above, we have determined protein requirements across different life cycles (Table 1), including:

  • Young adult men.8 
  • Six- to ten-year-old children.9 
  • Pregnant women during early (16 week) gestation and late (36 week) gestation.10 
  • Elderly women and men over the age of 65.11,12
  • Women over 80.13

Our daily protein recommendation estimates are 30–70% higher than the current recommendations. However, when these higher protein needs are expressed as a percentage of total calories you eat each day (instead of grams per body weight), they still fall within the recommended protein range of 10–20% of your daily calories. That’s called the Acceptable Macronutrient Distribution Range (AMDR).

In contrast, the older DRI guidelines suggest just 7–10% of your daily calories should come from protein—which is now considered too low to be realistic or optimal for most people.

Soy: A Complete Protein
Beyond the amount of protein, the type of protein is an important consideration, and is currently extensively being discussed by the Food and Agriculture Organization (FAO).14,15,16  Protein quality is defined as the capacity of food sources to provide individual amino acids in sufficient quantity to the body. In general, animal sources are considered of higher quality, since they contain all essential amino acids at higher concentrations on a mg/g protein basis.

Soy and other plant sources, such as legumes and pulses, are considered good quality protein sources. But in general, plant proteins are low in one or more essential amino acids; for example, cereals are low in lysine, and pulses/legumes are low in methionine. Furthermore, plant protein sources are also affected by cooking and processing methods and by the presence of anti-nutritional factors.17

How Much Protein Do You Need to Fuel Your Body?
However, unlike other plant sources, soy protein is one of the few plant-based protein sources that’s comparable to animal protein. It contains all nine amino acids that your clients need to build and repair tissue. Encourage them to add high-quality soy foods like tofu, edamame, tempeh, and soy milk to their meals to reap the benefits of this protein-packed ingredient.

Protein nutrition plays a critically important role in overall health. However, current protein recommendations may not be adequate to meet our needs at different life stages. A variety of protein sources can contribute to a balanced diet, and plant-based proteins such as soy offer a sustainable option. In addition, soy is a complete protein that includes all nine amino acids our bodies need.

Table 1. Protein Requirements Determined in Humans vs Recommendations across the Life Cycle

 

DRI1(2005)

IAAO2

 

g/kg/day

g/kg/day

% kcal

Young Adult Men

 

 

 

EAR3

0.66

0.93

~10%

RDA4

0.80

1.2

~13%

Children (6-10 y)

 

 

 

EAR

0.76

1.3

~9%

RDA

0.95

1.55

~10%

Pregnant Women (~16 week gestation)

 

EAR

0.88

1.22

~13%

RDA

1.1

1.66

~18%

Pregnant Women (~36 week gestation)

 

EAR

0.88

1.52

~17%

RDA

1.1

1.77

~20%

Elderly Women (>65 y)

 

 

EAR

0.66

0.96

~13%

RDA

0.80

1.29

~15%

Elderly Women (80+ y)

 

 

EAR

0.66

0.85

~10 %

RDA

0.80

1.15

~13 %


1Dietary Reference Intakes; 2Indicator Amino Acid Oxidation derived requirement estimates; 3Estimated Average Requirement; 4Recommended Dietary Allowance

REFERENCES

  1. R Elango, A Laviano. From old to new roles of protein sources and individual amino acids in clinical nutrition. Current Opinion in Clinical Nutrition & Metabolic Care. 2019; 22 (1): 58-59.
  2. DRI 2005. Institute of Medicine, Food and Nutrition Board, Dietary Reference Intakes: Energy, Carbohydrate, Fiber, fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Washington DC: The National Academy Press 2005.
  3. FAO 2007. Protein and amino acid requirements in human nutrition. Report of a joint WHO/FAO/UNU expert consultation. Geneva, Switzerland. 2007 (WHO Technical Report Series, No. 935).
  4. Rand WM, Pellett PL, and Young VR. Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. Am J Clin Nutr. 2003; 77: 109-127.
  5. Elango R, Ball RO, Pencharz PB. Recent advances in determining protein and amino acid requirements in humans. Br J Nutr. 2012;108:S22-30.
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  9. Elango R, Humayun MA, Ball RO, and Pencharz PB. Protein requirement of healthy school-age children determined by the indicator amino acid oxidation method. Am J Clin Nutr. 2011;94:1545-1552.
  10. Stephens TV, Payne M, Ball RO, Pencharz PB, Elango R. Protein requirements of healthy pregnant women during early and late gestation are higher than current recommendations. J Nutr. 2015;145:73-8.
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  13. Tang M, McCabe GP, Elango R, Pencharz PB, Ball RO, Campbell WW. Assessment of protein requirement in octogenarian women with use of the indicator amino acid oxidation technique. Am J Clin Nutr. 2014;99(4):891-8.
  14. Food and Agriculture Organization 2013. Dietary protein quality evaluation in human nutrition. Report of an FAO Expert Consultation. Food and nutrition paper No. 92. FAO, Rome.
  15. Food and Agriculture Organization 2014. Research approaches and methods for evaluating the protein quality of human foods. Report of a FAO Expert Working Group. Food and Agriculture Organization (FAO) of the United Nations. Rome 2014. (ISBN 978-92-5-108695-7)
  16. Food and Agriculture Organization 2018. Protein quality assessment in follow-up formula for young children and ready to use therapeutic foods. (ISBN 978-92-5-131120-2)
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