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Vegan For Life
by Jack Norris, RD &
Ginny Messina, MPH, RD
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Protein

(Last updated December, 2010.)

Summary

The most important thing to be aware of regarding protein in vegan diets is that you need to get enough of the amino acid lysine. Make sure you read the section on lysine below and check out the high-lysine foods. Beyond that, there is evidence that erring on the side of more protein (1.0 to 1.1 grams of protein per kg of healthy body weight per day for adults) is a good idea, and especially for people 60 years and older.

Contents

Introduction

Protein is important for maintaining muscle and bone mass, for keeping the immune system strong, and to prevent fatigue.

People not familiar with vegan nutrition often assume it is terribly hard to get enough protein on a vegan diet, and that's if they even think there is any protein in plant foods at all (how they think vegans survive is an interesting question, though many of them probably don't think we do). On the other hand, once "educated", most vegans have the diametrically opposite view, considering it impossible for someone not to get enough protein on a vegan diet.

The truth lies somewhere in the middle. It is easy to get enough protein on a vegan diet if you eat multiple servings of high-lysine foods (legumes, seitan, quinoa, pistachios, and pumpkin seeds) each day. But there are many vegans who are probably not eating enough high-lysine foods.

Legumes include soybeans and their products (tempeh, tofu, soy milk, soy meats, etc.), beans (garbanzo, kidney, pinto, etc.) and their products (falafel, hummus, refried, etc.), peas (green, split, black-eyed, etc.), lentils, and peanuts.

Vegans who do not eat enough calories to maintain their weight also need to pay special attention to making sure they are getting enough protein.

High Quality or Complete Proteins

Proteins are made out of chains of amino acids. Some amino acids can be made by the body (generally from other amino acids), but some cannot. The ones that cannot are known as "essential" or "indispensable."

Twenty amino acids are used to build protein, but they are not the only amino acids. Carnitine and taurine are amino acids which are not building blocks of protein, but the discussion here is limited to the protein amino acids.

Because some amino acids are essential, the RDA for amino acids should be as important as the RDA for protein. But because the RDA for protein takes into account the RDA for amino acids, the amino acid RDA is rarely mentioned. The essential amino acids are found in fairly consistent amounts in average Western diets and the RDA for protein is calculated with typical diets in mind.

Proteins in the human body tend to have a consistent percentage of the essential amino acids. The percentages of essential amino acids in both animal and soy products closely mimic those found in human proteins, and they are, therefore, considered complete or high-quality protein. Non-soy plant proteins have a lower percentage of at least one amino acid, although all legume products are pretty close to soy.

Some people are under the false impression that all non-soy plant foods are completely devoid of at least one essential amino acid. The truth is that all plant proteins have some of every essential amino acid (see Table 3). As a general rule, legumes are lower in the amino acid methionine while most other plants foods are lower in lysine.

In an effort to make sure vegetarians were getting enough of all the amino acids, in the early 1970s in her book Diet for a Small Planet, Frances Moore Lappe popularized the idea of combining plant proteins at each meal in order to get a "complete" protein. By mixing beans and grains, you can make sure that you are getting both methionine and lysine at each meal.

It is now well known that our livers store the various essential amino acids and so it's not critical to combine different protein sources at each meal. The 2009 American Dietetic Association's Position Paper on Vegetarian Diets says:

"Plant protein can meet requirements when a variety of plant foods is consumed and energy needs are met. Research indicates that an assortment of plant foods eaten over the course of a day can provide all essential amino acids and ensure adequate nitrogen retention and use in healthy adults, thus complementary proteins do not need to be consumed at the same meal."

For more information on which foods have "complete" proteins, see JackNorrisRd.com blog post, Complete Proteins.

Lysine: The Limiting Amino Acid in Vegan Diets

Before getting into a somewhat technical discussion about the protein needs of vegans, let's just cut to the chase - the RDA for lysine is more important than for protein. If you meet lysine requirements on a vegan diet, you will most likely meet protein requirements.

Per serving, legumes and seitan are the foods highest in the amino acid lysine. Tofu, tempeh, soy meats, lentils, and seitan are the highest, followed by other legume foods. Quinoa, pistachios, and pumpkin seeds are also decent sources of lysine.

It is very hard to design a vegan diet that meets lysine requirements for a person who does not exercise daily without including legumes, seitan, quinoa, pistachios, or pumpkin seeds without having too many calories. It is much easier to do for regular exercisers whose calorie requirements are higher - the low lysine foods will add up to provide enough. While many vegan, raw foodist athletes appear to thrive on the diet many raw foodist non-athletes struggle with raw diets; it might be the case that part of this is due to the athletes eating more calories and thus meeting lysine needs with low lysine foods.

Table 1. US RDA & Vegan Recommendations
Age Protein RDA
(g/kg)a
Lysine RDA
(mg/kg)a
0 - 6 mos 1.5 71
7 - 12 mos 1.5 71
1 - 3 yrs 1.1 52
4 - 13 yrs 0.95 45
14 - 18 yrs 0.85 40
18 - 59 0.8 38
≥ 60 .80 - 1.3b 38 - 62c
pregnancyd 1.1 52
lactation 1.1 52
A. per kg of healthy body weight.
B. RDA for older people is the lower number, but many experts recommend up to higher number.
C. Lysine range to correspond to higher protein recommendation explained in footnote B.
D. Based on pre-pregnancy weight.

Table 3 below allows you to put in your ideal body weight (IBW), an explanation of which is in the table footer, click the submit button, and the table will give you the RDA for lysine (for an adult). You can then see how much lysine is in typical vegan foods and what it takes for you to get enough. Table 1 (left) lists the lysine RDA for all age groups.

Protein Needs for People Over 60

Many recent papers have suggested that people over 60 years old are better off with 1.0 to 1.3 g/kg of protein per day (8, 9, 10, and many more). Most of this research is supported by or connected to people who have done work supported by animal agriculture trade organizations (8, 9, and many more).

Their argument, based on some research, is that older people are less efficient at maintaining muscle and bone and therefore need more protein. These arguments are convincing enough that, despite their support from animal agriculture, it is probably a good idea for older people to get more protein. Because of this, Table 1 gives a range of recommendations for higher lysine and protein needs for those 60 and older.

Protein Recommendations for Vegans

Aside from lysine, how much total protein do vegans need?

Until recently, we thought this was a pretty straightforward answer: vegans either need to meet the RDA or possibly 10% higher due to plant proteins being harder to digest.

The RDA for protein is supposed to cover the needs of 97 to 98% of the population. It is currently set at .80 grams per kilogram of healthy body weight per day. In addition to the RDA, there is also an Estimated Average Requirement (EAR) for protein, and it is .66 g/kg for adults 19 to 50 years old (1). The EAR is supposed to be how much protein the average person requires.

The RDA for the normal population is based on nitrogen balance studies, especially a 2003 meta-analysis of them (3). Nitrogen balance studies are used because nitrogen is a component of protein that fat, carbohydrate, and alcohol do not have. The studies are done by measuring how much nitrogen someone eats and then subtracting how much they lose through urine, feces, hair, sweat, etc. If they lose more than they eat, then they are in negative nitrogen balance and need more protein. If they lose as much as they eat, they are considered in nitrogen balance and that is determined to be the ideal protein amount to eat.

With all the commotion regarding vegans and protein for the past 40 years, one would think we would have a plethora of nitrogen balance studies performed on actual vegans. Guess how many we have? None.

The Food and Nutrition Board, who sets the RDAs, says, "[A]vailable evidence does not support recommending a separate requirement for vegetarians who consume complementary mixtures of plant proteins[.]" But what is that available evidence?

There have been two studies looking at nitrogen balance using a vegan diet (on people who are typically not vegan).

A 1965 study had two parts (11). In the first part, eight young men were fed a vegan diet of .50 g/kg of protein per day, with the amino acid profile matching that of milk. With some small exceptions, they did not stay in nitrogen balance. No surprises there. In the second part of the study, they increased the protein to .75 g/kg using .25 g/kg of soy protein per day and the subjects were, for the most part, in nitrogen balance. This indicates that .75 g/kg might be enough protein for vegans, especially young men, but it might require .25 g/kg of that protein to be soy (or at least legumes).

A 1967 study found that protein for people eating a vegan diet (for a 3-week period) was 2.6% less digested than the protein in a non-vegetarian diet (4). The diets in this study averaged .91 g/kg of protein per day (my calculations based on weights and heights given), of which .55 g/day were legume protein. On the vegan diet, 9 out of 12 of the participants were in nitrogen balance.

A 1986 study fed young adult males a near-vegan diet (except for 41 g of dried, skim milk) for 90 days, using 1 g/kg of body weight per day (1). Some of the protein was from beans, but it is not clear how much. Only one out of the eight subjects showed a negative nitrogen balance.

Table 2. Plant Protein Studies
Study Legume Protein
(g/kg)a
Protein
(g/kg)a
Result
1965, Doyle amino acids matched milk 0.50 Subjects not in nitrogen balance
1965, Doyle amino acids matched milk 0.75 100% in nitrogen balance
1967, Register 0.55 0.91 75% in nitrogen balance
1986, Yanez small amount 1.00 7 out of 8 in nitrogen balance
2000, Caso not clear 1.09 12% lower albumin synthesis than controls
2000, Caso at least .25 1.34 normal albumin synthesis
1999, Haddad 0.36 1.04 normal albumin levels
2011, Andrich lysine intake 79% RDA 1.0 muscle mass similar to omnivores
aper kg of healthy body weight

In addition to nitrogen balance, protein needs can be measured by the rate of albumin synthesis. Albumin is a protein in the blood that responds to different amounts of dietary protein.

A 2000 study of healthy men showed a 12% reduced rate of albumin synthesis when eating a diet of 63% plant protein compared to 26% plant protein (each for 10 days and equal amounts of total protein) (6). When 18 g/day of soy protein was added (increasing the plant protein percentage to 78 and total protein from 78 g/day to 96 g/day), albumin synthesis returned to normal. I have estimated the grams of protein per kg of healthy body weight per day in this study and they were eating about 1.09 g/kg without the soy, and 1.34 with the soy an increase of 23% (7). We do not know if that much protein was required to return albumin synthesis to normal, and it is possible that 10 days was not long enough to see if someone's albumin synthesis would become more efficient on a primarily plant-based diet.

The synthesis of two other proteins, prealbumin and transferrin, were also reduced on 63% plant protein. The fact that transferrin, an iron transport protein, decreased is interesting. Lysine supplements have been found to increase iron absorption so it's likely these subjects were not getting enough lysine.

On the other hand, a 1999 cross-sectional study on vegans found them to have significantly higher serum albumin levels than non-vegetarians (12). The vegans were eating 1.04 grams of protein per kg of body weight (based on a BMI of 22). They were eating approximately .36 g/kg of legume protein. The authors stated, "Although serum albumin may not be a sensitive indicator of protein nutriture, the higher concentrations suggest that the diets of the vegan participants were adequate in protein."

A study out of Boston published in 2011 but performed using data collected during the 1980s, found that vegan and non-vegan, middle-aged women had similar levels of muscle mass despite differences in protein intake of 1.0 g/kg/day for vegans and 1.3 g/kg/day for omnivores (14). However, the muscle mass was not measured directly - rather it was estimated using formulas based on creatinine clearance (a byproduct of muscle metabolism). The researchers believed the formulas to be accurate, but since they have not been validated on vegans it should be viewed with some uncertainty. At 30 mg/kg/day, the vegan women did not meet the RDA for lysine which is 38 mg/kg/day. However, the study showed the vegan women to be consuming only 1511 kcal/day vs. 1866 kcal/day for the omnivores, yet their body mass indexes were very similar at 20.0 and 20.7 respectively. This could indicate that food intake for the vegans was underestimated, possibly due to a lack of data on vegan foods.

So where does all this research leave us? The results are compiled in Table 2. It is not obvious what they indicate for the protein needs of vegans, but an estimate is that vegans might benefit from 1.0 to 1.1 g/kg of protein. What is really needed is nitrogen balance studies on actual vegans.

Protein Needs of Athletes

The Institute of Medicine, who sets the RDAs, does not recommend higher protein intakes for athletes. However, in a 2009 joint position paper on nutrition and athletic performance, the American College of Sports Medicine (ACSM), the American Dietetic Association (ADA), and Dietitians of Canada recommend higher protein intakes for athletes. They say:

  • Endurance athletes - "Nitrogen balance studies suggest that dietary protein intake necessary to support nitrogen balance in endurance athletes ranges from 1.2 to 1.4 g/kg/day."
  • Strength athletes - "Recommended protein intakes for strength-trained athletes range from approximately 1.2 to 1.7 g/kg/day." and "The amount of protein needed to maintain muscle mass may be lower for individuals who routinely resistance train because of more efficient protein use."
  • Vegetarians - "Because plant proteins are less well digested than animal proteins, an increase in intake of approximately 10% protein is advised. Therefore, protein recommendations for vegetarian athletes approximate 1.3–1.8 g/kg/day."

Nitrogen Balance Methods Critiqued

In 2010, a group of researchers from The Hospital for Sick Children in Toronto wrote a paper suggesting that the methods for determining the DRIs for protein (which includes the RDA) were underestimating protein needs (5). One of the authors, Dr Paul B. Pencharz, was a member of the Panel on DRIs for macronutrients and a member of the Joint WHO/FAO/United Nations University (UNU) Expert Consultation on Protein and Amino Acid Requirements in Human Nutrition. They write:

The current recommendations for protein intakes in adults are primarily based on the reanalysis of existing nitrogen balance studies [1,12]. The nitrogen balance technique has inherent methodological limitations, which lead to an underestimation of the requirement estimate. Furthermore, the application of a single linear regression analysis to identify zero nitrogen balance is not appropriate because the nitrogen intake response relationship is not linear. On the basis of these concerns, we reanalyzed published nitrogen balance studies using two-phase linear regression analysis. We also applied the IAAO method to determine total protein requirements in adults. The mean and population-safe intakes based on the reanalysis were determined to be 0.91 and 1.0 g protein/kg/day and 0.93 and 1.2 g/kg/day, respectively, based on the IAAO method. These new values are approximately 40% higher than the current recommendations, and therefore, there is an urgent need to reassess recommendations for protein intake in adult humans.

They say that the inherent methodological errors in nitrogen balance studies are that nitrogen intakes are overestimated and nitrogen loss is underestimated, leading to false nitrogen balance at lower protein levels.

The IAAO method referenced above is described in this excerpt:

[The IAAO method is] based on the concept that when one indispensable amino acid (IDAA) is deficient in the diet, then all other amino acids, including the indicator amino acid (another IDAA, usually L-[1-13C]phenylalanine), will be oxidized [5]. With increasing intake of the limiting amino acid (or total protein), oxidation of the indicator amino acid will continue to decrease, reflecting increasing incorporation into protein. Once the requirement is met for the limiting amino acid, there will be no further change in the oxidation of the indicator amino acid.

In other words, this group of researchers considers the average protein requirement to be .91 - .93 g/kg/day and the amount to cover 97% to 98% of the population (equivalent to the RDA) to be 1.0 - 1.2 g/kg/day.

Erring on the side of more protein is probably a good idea for vegans.

Links

Table 3: Protein & Amino Acids in Common Foods

In the box below, you can enter your healthy or ideal body weight (IBW) and click the button. Table 3 will show you how much of any given food you need to meet the RDA for protein and amino acids. This is not to suggest you get all your amino acids from one food, but it can give an idea of what sort of combinations might be required.

If you do not know what your IBW is, put your height in either inches or centimeters (and choose the appropriate selection from the drop down box). See the table footer for an explanation.

Enter:
Table 3. Protein & Amino Acid Content of Plant Foods
RDA for a 140 lb Person
USA Recommended Dietary Allowance (RDA)
protein in g   |   amino acids in mg
PROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
RDA - per kg of healthy body weight0.814194238193320524
RDA for 140 lb. person518911209267324181209210012733181527
Soy
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Edamame
Serving: 0.50 cup (78 g)
8.420723357757720463825798251
Number of servings to meet RDA
6.04.35.24.64.25.93.35.03.26.1
Soy Milk
Serving: 1.00 cup (245 g)
9.2174353590439213644277105345
Number of servings to meet RDA
5.55.13.44.55.55.73.34.63.04.4
Tempeh
Serving: 0.50 cup (83 g)
15.43877301187754305901661161764
Number of servings to meet RDA
3.32.31.72.33.24.02.31.92.02.0
Tofu - firm
Serving: 0.50 cup (126 g)
10.22845599175821771013518155573
Number of servings to meet RDA
5.03.12.22.94.26.82.12.52.12.7
Legumes
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Black Beans - cooked
Serving: 0.50 cup (86 g)
7.621233660952319762732190399
Number of servings to meet RDA
6.74.23.64.44.66.13.34.03.53.8
Garbanzos (Chick Peas) - cooked
Serving: 0.50 cup (82 g)
7.320031251748619356927070305
Number of servings to meet RDA
7.04.53.95.25.06.33.74.74.55.0
Kidney Beans - cooked
Serving: 0.50 cup (89 g)
7.721433961352719863132391402
Number of servings to meet RDA
6.64.23.64.44.66.13.33.93.53.8
Lentils - cooked
Serving: 0.50 cup (99 g)
8.925138664762419368032080444
Number of servings to meet RDA
5.73.53.14.13.96.33.14.04.03.4
Peanut Butter
Serving: 2.00 T (32 g)
8.020428452329020274627678339
Number of servings to meet RDA
6.44.44.35.18.36.02.84.64.14.5
Peanuts - dry roasted
Serving: 0.33 cup (48 g)
11.42894017404102861055391111478
Number of servings to meet RDA
4.53.13.03.65.94.22.03.32.93.2
Pinto Beans - refried
Serving: 0.50 cup (121 g)
6.417530354444814352923576369
Number of servings to meet RDA
8.05.14.04.95.48.54.05.44.24.1
Nuts & Seeds
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Almonds
Serving: 0.25 cup (36 g)
7.619925153220712256221477292
Number of servings to meet RDA
6.74.54.85.011.79.93.75.94.15.2
Cashews
Serving: 0.25 cup (34 g)
5.213725044028019143920381356
Number of servings to meet RDA
9.86.54.86.18.66.34.86.33.94.3
Pecans
Serving: 0.25 cup (25 g)
2.3658314871831587623102
Number of servings to meet RDA
22.113.714.618.134.114.613.316.713.815.0
Pistachios
Serving: 0.25 cup (31 g)
6.415829449236721649621687388
Number of servings to meet RDA
8.05.64.15.46.65.64.25.93.73.9
Pumpkin seeds - roasted
Serving: 0.25 cup (30 g)
8.8227373704360272823291168460
Number of servings to meet RDA
5.83.93.23.86.74.42.64.41.93.3
Sunflower Seeds
Serving: 0.25 cup (32 g)
6.217230945125425748925294357
Number of servings to meet RDA
8.25.23.95.99.54.74.35.13.44.3
Walnuts - chopped
Serving: 0.25 cup (29 g)
4.511418334212413032717450220
Number of servings to meet RDA
11.37.86.67.819.59.36.47.36.46.9
Grains
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Bread - white
Serving: 2.00 slice (50 g)
4.18916129011215932012148180
Number of servings to meet RDA
12.410.07.59.221.67.66.610.56.68.5
Bread - whole wheat
Serving: 2.00 slice (56 g)
7.378125227931302569752152
Number of servings to meet RDA
7.011.49.711.826.09.38.213.16.110.0
Buckwheat - groats roasted
Serving: 1.00 cup (168 g)
5.713321335628917132721782291
Number of servings to meet RDA
8.96.75.77.58.47.16.45.93.95.2
Corn
Serving: 1.00 cup (82 g)
5.415021858823215846021838314
Number of servings to meet RDA
9.45.95.54.510.47.74.65.88.44.9
Flour Tortilla
Serving: 1.00 med (46 g)
4.0901412769815432211349164
Number of servings to meet RDA
12.79.98.69.724.77.96.511.36.59.3
Oatmeal - boiled
Serving: 1.00 cup (234 g)
5.9126271505316335568225236374
Number of servings to meet RDA
8.67.14.55.37.73.63.75.71.34.1
Quinoa - cooked
Serving: 1.00 cup (185 g)
8.123529048344229549624296342
Number of servings to meet RDA
6.33.84.25.55.54.14.25.33.34.5
Rice - brown, med grain
Serving: 1.00 cup (195 g)
4.511519137217215640216658265
Number of servings to meet RDA
11.37.76.37.214.17.85.27.75.55.8
Rice - white, med grain
Serving: 1.00 cup (186 g)
4.410419236616019538515852270
Number of servings to meet RDA
11.68.66.37.315.16.25.58.16.15.7
Seitan
Serving: 3.00 oz (85 g)
31.0671129322476561077291583901498
Number of servings to meet RDA
1.61.30.91.23.71.10.71.50.01.0
Spaghetti - white
Serving: 1.00 cup (140 g)
6.713625845612729249817685284
Number of servings to meet RDA
7.66.64.75.919.04.14.27.23.75.4
Spaghetti - whole wheat
Serving: 1.00 cup (140 g)
7.517529051016527556620097323
Number of servings to meet RDA
6.85.14.25.214.74.43.76.43.34.7
Vegetables
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Baked Potato
Serving: 1.00 med (173 g)
4.39317526026312135115767244
Number of servings to meet RDA
11.89.66.910.39.210.06.08.14.76.3
Broccoli - cooked, chopped
Serving: 1.00 cup (156 g)
3.6821802162348824415248212
Number of servings to meet RDA
14.110.96.712.410.313.78.68.46.67.2
Carrot - 5 12 inches long
Serving: 1.00 small (50 g)
0.520385151525196635
Number of servings to meet RDA
108.344.531.852.447.423.341.213.353.043.6
Kale - cooked, shredded
Serving: 1.00 cup (130 g)
2.5521481731485621511130135
Number of servings to meet RDA
20.417.18.215.416.321.69.811.510.611.3
Romaine Lettuce - shredded
Serving: 1.00 cup (56 g)
0.716585458226042648
Number of servings to meet RDA
72.755.720.849.541.755.035.030.353.031.8
Tomato
Serving: 1.00 med (123 g)
1.117223133185033722
Number of servings to meet RDA
46.352.455.086.273.367.242.038.645.569.4
Fruit
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Apple
Serving: 1.00 med (138 g)
0.4781817298117
Number of servings to meet RDA
127.3127.3151.1148.5142.2604.5233.3159.1318.289.8
Banana
Serving: 1.00 med (118 g)
1.3913380592069331155
Number of servings to meet RDA
39.29.836.633.441.060.530.438.628.927.8
Orange
Serving: 1.00 med (131 g)
1.2243330623962201252
Number of servings to meet RDA
42.437.136.689.139.031.033.963.626.529.4
Strawberries - whole
Serving: 1.00 cup (144 g)
1.0172349371259291227
Number of servings to meet RDA
50.952.452.654.565.4100.835.643.926.556.6
Seaweed
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Spirulina - dried
Serving: 1.00 tbsp (7 g)
4.07622534621212637520865246
Number of servings to meet RDA
12.711.75.47.711.49.65.66.14.96.2
Protein Powders
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Naturade Soy Protein
Serving: 0.33 cup (28 g)
24.061811781939155264021849123051157
Number of servings to meet RDA
2.11.41.01.41.61.91.01.41.01.3
Naturade Soy-Free Protein
Serving: 0.33 cup (28 g)
22.053311821785145544519579182281115
Number of servings to meet RDA
2.31.71.01.51.72.71.11.41.41.4
Animal
FoodPROHISISOLEULYSMET
CYS
PHE
TYR
THRTRPVAL
Beef - ground, 15% fat, pan-broiled
Serving: 3.00 oz (85 g)
20.96819241631173374514598111081028
Number of servings to meet RDA
2.41.31.31.61.41.61.41.62.91.5
Chicken - roasted
Serving: 1.00 leg (52 g)
14.1417708102811525621004583158684
Number of servings to meet RDA
3.62.11.72.62.12.22.12.22.02.2
Egg - hard boiled
Serving: 1.00 large (50 g)
6.314934353745234259130276384
Number of servings to meet RDA
8.16.03.55.05.33.53.64.24.24.0
Milk - 2% fat
Serving: 1.00 cup (244 g)
8.117844780856946476825198532
Number of servings to meet RDA
6.35.02.73.34.22.62.75.13.22.9
Tuna
Serving: 3.00 oz (85 g)
21.76389991762199287415799502431117
Number of servings to meet RDA
2.31.41.21.51.21.41.31.31.31.4

Protein is measured in grams   |   Amino acids are measured in mg

PRO = Protein |   HIS = Histidine |   VAL = Valine |   MET CYS = Methionine + Cysteine
ISO = Isoleucine |   THR = Threonine |   LEU = Leucine |   PHE TYR = Phenylalanine + Tyrosine
TRP = Tryptophan |   LYS = Lysine |   IBW = Ideal Body Weight

The RDA's are given in grams per kilogram of body weight per day. Fat mass does not require much protein for maintenance, so "body weight" is generally interpreted to mean "ideal" or "healthy" body weight even though the RDA's do not specify that. The formula here for calculating IBW by way of height uses a body mass index of 22 (20 - 25 is considered healthy). Muscular people without much excess body fat should probably use their current body weight rather than height.

The essential amino acid methionine is paired with the non-essential cysteine, and the essential amino acid phenylalanine is paired with the non-essential tyrosine. That is because the RDA is calculated for these pairs of amino acids together, assuming there are similar ratios in most foods. In plant foods, there are about equal amounts of methionine and cysteine, and usually more phenylalanine than tyrosine.

Sources:

  • RDAs were taken from Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (2002) by the Food and Nutrition Board (FNB) of the Institute of Medicine, p. 680. Link
  • The protein and amino acid content of foods was taken from the USDA National Nutrient Database and Naturade protein powder labels.
  • Amino acid content for pumpkin seeds was taken from the USDA database entry for Food #12016, Seeds, pumpkin and squash seed kernels, roasted, without salt. According to correspondence with Robin G. Thomas, MS, RD of the USDA Nutrient Data Laboratory, the entries for 12014, 12016 and 12516 are for pumpkin seeds only (i.e., not squash seeds also) (January 2013).
  • Seitan information is extrapolated from White Wave seitan label. The label lists wheat gluten, garbanzo flour, and soy flour as the main sources of protein. For this table, it was assume that 5% of the protein was from garbanzo protein and 5% from soy flour. Wheat gluten amino acid composition was taken from: Rombouts I, Lamberts L, Celus I, Lagrain B, Brijs K, Delcour JA. Wheat gluten amino acid composition analysis by high-performance anion-exchange chromatography with integrated pulsed amperometric detection. J Chromatogr A. 2009 Jul 17;1216(29):5557-62. Epub 2009 Jun 3. (link), and Molecular weight for amino acids was taken from ExPASy The amount of tryptophan in wheat gluten is negligible, and thus no amount is listed for seitan. However, the soy and garbanzo protein alone will provide 38 mg of tryptophan per serving (which is not included in the table since it is not clear how much soy and garbanzo protein is actually in seitan).

References

1. Yáñez E, Uauy R, Zacarías I, Barrera G. Long-term validation of 1 g of protein per kilogram body weight from a predominantly vegetable mixed diet to meet the requirements of young adult males. J Nutr. 1986 May;116(5):865-72. (Link)

2. Dietary Reference Intakes: Macronutrients. National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. DRI table for carbohydrate, fiber, fat, fatty acids and protein. (Link)

3. Rand WM, Pellett PL, Young VR. Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. Am J Clin Nutr. 2003 Jan;77(1):109-27. (Link)

4. Register UD, Inano M, Thurston CE, Vyhmeister IB, Dysinger PW, Blankenship JW, Horning MC. Nitrogen-balance studies in human subjects on various diets. Am J Clin Nutr. 1967 Jul;20(7):753-9. (Link)

5. Elango R, Humayun MA, Ball RO, Pencharz PB. Evidence that protein requirements have been significantly underestimated. Curr Opin Clin Nutr Metab Care. 2010 Jan;13(1):52-7. (Link)

6. Caso G, Scalfi L, Marra M, Covino A, Muscaritoli M, McNurlan MA, Garlick PJ, Contaldo F. Albumin synthesis is diminished in men consuming a predominantly vegetarian diet. J Nutr. 2000 Mar;130(3):528-33. (Link)

7. Calculations:
Average healthy body weight of the men based on a BMI of 22 and average height of 1.74 m = 66.6 kg
78 g protein per 66.6 kg = 1.17 g/kg
96 g protein per 66.6 kg = 1.44 g/kg
Actual average body weight of the men was 77 kg
78 g protein per 77 kg = 1.01 g/kg
96 g protein per 77 kg = 1.25 g/kg
Averageing the healthy body weight with the actual body weight gives 1.09 and 1.34 g/kg

8. Gaffney-Stomberg E, Insogna KL, Rodriguez NR, Kerstetter JE. Increasing dietary protein requirements in elderly people for optimal muscle and bone health. J Am Geriatr Soc. 2009 Jun;57(6):1073-9. (Link)

9. Paddon-Jones D, Short KR, Campbell WW, Volpi E, Wolfe RR. Role of dietary protein in the sarcopenia of aging. Am J Clin Nutr. 2008 May;87(5):1562S-1566S. (Link)

10. Morais JA, Chevalier S, Gougeon R. Protein turnover and requirements in the healthy and frail elderly. J Nutr Health Aging. 2006 Jul-Aug;10(4):272-83. (Link)

11. Doyle MD, Morse LM, Gowan JS, Parsons MR. Observations on nitrogen and energy balance in young men consuming vegetarian diets. Am J Clin Nutr. 1965 Dec;17(6):367-76. (Link)

12. Haddad EH, Berk LS, Kettering JD, Hubbard RW, Peters WR. Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr. 1999 Sep;70(3 Suppl):586S-593S. (Link)

13. 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;109:509-527. Link.

14. Andrich DE, Filion ME, Woods M, Dwyer JT, Gorbach SL, Goldin BR, Adlercreutz H, Aubertin-Leheudre M. Relationship between essential amino acids and muscle mass, independent of habitual diets, in pre- and post-menopausal US women. Int J Food Sci Nutr. 2011 Nov;62(7):719-24. Epub 2011 May 16. (Link)

Also Reviewed

Evans WJ. Protein nutrition, exercise and aging. J Am Coll Nutr. 2004 Dec;23(6 Suppl):601S-609S. (Link)