protein

Foods Richest in protein

About protein

Basic description

Protein is the most widely recognized macronutrient in public health nutrition.

U.S. dietary guidelines have emphasized protein intake for over a century. The name itself derives from the Greek protos, meaning “first.” That historical priority reflects the structural reality: proteins serve as enzymes, hormones, structural scaffolds, transport molecules, and immune effectors. The number of distinct biological functions assigned to proteins far exceeds those of any other macronutrient class. The table below summarizes where proteins operate across body systems.

Body System

Function

Examples of Proteins Involved

Digestive

serves as digestive enzymes

amylases, chymotrypsin, disaccharides, lipases, peptidases, proteases, ribonucleases

Connective tissue (and extracellular fluid)

provide elasticity, provide fluid gel structures, allow for adhesiveness

amylases, chymotrypsin, disaccharides, lipases, peptidases, proteases, ribonucleases

Muscle

provide components that allow for contraction

actin, myosin, troponin, tropomysin, vinculin

Endocrine

serve as hormones

insulin, growth hormone, thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH)

Nervous

provide amino acids for neurotransmitters

epinephrine, norepinephrine, serotonin, melatonin

Genetic

formation of DNA and RNA

histones, nucleic acid polymerizing enzymes

Cardiovascular

maintain correct blood pressure and transport a variety of substances

albumin, alpha-globulin, beta-globulin, fibronectin, Complement A

Cellular

provide structural integrity and protection

actin, tubulin, spectrin, intermediary filaments

Signaling

transfer chemical messages into and out of cells

GCPRs (G-protein coupled receptors)

Energy production

promote oxygen-based energy production inside of mitochondria

ATP synthetase, NADH reductase, succinate dehydrogenase

Detoxification

processing potential toxins to enable elimination from the body

cytochrome P450 enzymes, sulfotransferase enzymes, methyltransferase enzymes

Nearly every physiological process depends on at least one class of protein.

Half of WHF foods qualify as good, very good, or excellent protein sources. Every profiled food except extra virgin olive oil contains measurable protein. Reaching the 50-gram Daily Value (DV) requires surprisingly few selections: four ounces of cod, four ounces of tofu, and 1.5 cups of green peas together supply 50 grams. Total grams matter, but they do not capture protein quality.

“Protein quality” refers to the amino acid composition of a protein and how efficiently the body can use it. Amino acids are covered in their own nutrient profile, but several points about them are relevant here.

There are 20 different amino acids most commonly used to construct proteins. Different types of proteins require different combinations of amino acids because they have different roles to play in the body. Some proteins are quite small and only contain a few dozen total amino acids. Other proteins are extremely large and can contain tens of thousands of total amino acids. Most of the time, however, there are several hundred amino acids per protein, with several dozen of any particular amino acid. As you can see, it is common for proteins to provide significantly different amounts of both total and individual amino acids.

Proteins also function as delivery systems. Digestive proteases break them into individual amino acids or short peptide chains that the body absorbs and redistributes. A protein can be valuable both as an intact molecule (an enzyme, for instance) and as a source of its constituent amino acids.

Debate continues about the best scoring methods for protein quality (PDCAAS, DIAAS, and others are discussed in the amino acids profile). Regardless of scoring method, consuming proteins that supply sulfur-containing amino acids (methionine, cysteine), branched-chain amino acids (leucine, isoleucine, valine), and aromatic amino acids (phenylalanine, tryptophan, tyrosine) over a 3-4 day rolling window supports a full amino acid complement. Plant food groups that contribute distinct amino acid profiles include beans and legumes, nuts and seeds, vegetables, and whole grains. Animal foods across all categories (poultry, meats, seafood, dairy, eggs) supply complete amino acid profiles in each serving.

The DV of 50 grams per day is best understood as a floor, not an optimum. A growing body of research suggests benefits from higher intakes. An 1,800-calorie diet at 15% protein delivers 67 grams; at 20%, that rises to 90 grams. Studies using 15-20% protein are increasingly common, and many show metabolic advantages at these levels (see Role in Health Support below).

Role in health support

Every organ system depends on protein. All enzymes are proteins; so are hormones like insulin, neurotransmitters like serotonin, and structural molecules like collagen. The open question is not whether protein is needed, but what intake levels and amino acid profiles produce the best functional outcomes. Determining optimal enzyme activity from protein intake alone remains difficult because so many cofactors (minerals, B vitamins) are involved. The sections below summarize current evidence on dietary protein and specific health outcomes.

Maintaining the integrity of body structures

Proper functioning of muscles and healthy formation of connective tissue (the structure that supports and connects our organs) both require sufficient protein intake. In recent studies on aging, adequate protein intake has been associated with decreased risk of hip fracture. This association is likely to be related to the role of protein in supporting healthy muscles and connective tissue. Interestingly, there is some evidence of better support when protein is consumed at the level of 1.2 grams per kilogram of body weight versus 0.8 grams. Since a 154-pound person would weigh 70 kilograms, this lower amount would translate in 56 grams of protein for a 154-pound person, while the higher amount would translate into 84 grams. Of course, the sturdiness of the body depends on far more than just adequate nourishment, since the strength, flexibility, and resilience of muscles and connective tissue require healthy amounts of physical activity and other lifestyle practices.

Improved body composition

Protein intake has been a much-debated subject in relationship to body weight and body composition. As a general rule, no specific amount or quality of protein intake can single-handedly improve a person’s body composition or promote a healthier body weight. Body composition and body weight depend too heavily on many other factors, including calorie intake, fat intake, activity level, and hormonal balance - to name just a few. However, recent studies show potentially important roles for protein in helping to regulate appetite and alter various aspects of metabolism in a way that helps balance body composition. (In most studies, body composition was measured using body mass index, waist circumference, skinfold thickness, or similar measurements.) In addition, some studies show improved weight control when protein intake represents approximately 15-20% of total calorie intake rather than 10-15%. As mentioned earlier, an 1,800-calorie diet would provide 45 grams of protein at the 10% level, 67 grams of protein at the 15% level, and 90 grams of protein at the 20% level. In other words, a 15-20% protein diet would typically provide substantially more grams of total protein than the 50-gram Daily Value level.

In most published studies, intake levels associated with improved body composition fell in the 65-100 gram range, well above the 50-gram DV. One research group proposed roughly 30 grams per major meal as a target for weight regulation. That figure remains speculative; body composition depends heavily on physical activity, caloric balance, and hormonal factors. Still, the trend across studies points toward advantages at intakes above the DV.

Improved blood sugar regulation

Adequate protein in meals and snacks has long been a mainstay in dietary advice for improved blood sugar regulation. The benefits of protein-rich foods for blood sugar control are largely due to two factors. First, protein is a nutrient that digests at a moderate pace. Protein is one of three basic “macronutrients.” Macronutrients are nutrients that we need in relatively large (gram-sized) amounts. Among the three basic macronutrients, carbohydrates can often digest quite quickly. Fats, by contrast, often digest quite slowly. Protein is typically in the middle, and this intermediate position of protein digestion tends to help stabilize food digestion and blood sugar balance. Second, protein-rich foods tend to have very low glycemic index (GI) values. (While GI is related to speed of digestion, it is a measurement that is also related to other aspects of food digestion.) At WHF, the vast majority of our profiled foods (86 out of 100) have a GI value of either very low or low. Only 13 WHF have a medium GI score, and only 1 WHFood (potato) has a high GI score. Importantly, all of our Top 10 Protein-Rich foods score “very low” in GI, and all of our Top 25 Protein-Rich foods score either “very low” or “low”. By contrast, none of our 14 foods with either “medium” or “high” GI scores rank as good, very good, or excellent protein sources. So as you can see, there is a very natural fit between protein-rich foods and foods that help stabilize blood sugar levels.

While there is no question that protein-rich foods can help to stabilize blood sugar levels, there remain plenty of questions about the total amount of protein intake that is best for blood sugar control. Studies on type 2 diabetes and insulin resistance show some mixed findings with respect to protein intake levels. On the one hand, some studies show improved insulin resistance and blood sugar regulation with protein intake in the 20-30% of total calories range. We’ve also seen a study showing a slight but perhaps still significant decrease in hemoglobin A1c levels (a lab test used to determine average blood sugar level over a 2-3 month period of time) in persons with type 2 diabetes when consuming protein in the range of 26-32% total calories for 6 months. At the same time, however, several large-scale studies have failed to show similar results. We suspect that this inconsistency in research findings is mostly related to the overall quality of the diets being consumed, and to other factors that extend beyond diet. For example, excessive intake of calories, or excessive intake of processed foods, or intake of high glycemic index foods could easily offset any potential benefits associated with higher levels of protein intake. And in studies where these factors were not fully controlled, we would not expect to see benefits from protein intake above the Daily Value. Similarly, factors unrelated to diet - like amount of exercise - also play a major role in blood sugar and insulin balance.

In summary, it is clear that protein-rich foods can help improve blood sugar and insulin levels. Having protein-rich foods on a meal-by-meal basis seems important in this regard. However, it is not clear whether total protein intake above the DV level is consistently helpful for improving blood sugar balance, even though some studies show benefits from higher levels of protein intake.

Other potential health benefits

Two other areas of potential health benefit deserve special mention when considering protein intake. One area involves immune support, and the other area involves support of the cardiovascular system.

Antibodies are immunoglobulin proteins that identify and neutralize pathogens. The immune system also requires protein for complement proteins that support white blood cell function. Without adequate protein intake, antibody production drops. Kwashiorkor, a severe protein deficiency condition, is characterized in part by immune system collapse.

The connection between immune function and protein status has been well-studied in athletes. Changes in blood flow during high-intensity exercise place strong demands on the immune system and redistribution of white blood cells. In the hours following intense exercise, the ability of the immune system to conduct good surveillance of the body is easily compromised, and for this reason, sufficient protein intake to restore healthy immune function can be important. Some studies show that a helpful level of protein intake for training athletes may require at least 20% of total calories. While this percentage may not sound particularly high, it is important to remember that a training athlete may consume 2,500 calories per day or more. At this calorie level, 20% protein would mean about 125 grams or higher.

In some studies on aging, risk of inflammatory disease has been shown to decrease with protein intake of 1.0 - 1.5 grams per kilogram of body weight. For a person weighing 154 pounds, this formula would mean 70 - 105 grams of daily protein. However, we also want to point out that in some other studies on aging, high protein intake has been shown to have the opposite impact: in these studies, low protein, high carbohydrate diets have slowed down the decline in immune system problems when compared with high protein, low carbohydrate diets. We suspect that the conflicting results in this area of protein, immune system and aging are largely due to the fact that total protein grams are not sufficient in and of themselves to provide us with immune system support. Instead, this total amount of protein must be evaluated within the bigger context of protein quality, overall dietary intake, and overall body health (including the health of the lungs, kidneys, and other body systems that can become compromised over the course of aging).

Potential cardiovascular benefits from protein intake greater than the Daily Value have a second research area with mixed findings. In one study, the fat content of liver cells (in the form of triglycerides) was found to be increased by a high carbohydrate (60% of total calories) and low protein (5% of total calories) diet, in comparison to a high protein (30% of calories) and low carbohydrate (35% of calories) diet. Similarly, risk of coronary heart disease associated with an 1,800-calorie diet emphasizing plant protein (93 grams) was found to be somewhat lower than the risk associated with a similar diet containing only 49 grams of plant-based protein. However, other studies have found no difference in risk associated with moderate versus high levels of protein intake, and even when differences have been found, they have not turned out to be statistically significant. Finally, we have reviewed a large-scale study on high blood pressure showing an association between high levels of protein intake (in the vicinity of 100 grams per day) and significantly decreased risk of high blood pressure over an 11-year period of time.

Since no whole food consists of pure protein, these cardiovascular-related studies surely encourage us to place protein intake into a bigger context. If proteins come from low quality foods, or are woven into a poorly balanced overall diet, it seems unlikely for greater amounts to lower our risk of cardiovascular problems (or any other problems). However, within the context of a well-balanced, high-quality, whole foods diet, protein intake above the Daily Value may offer important benefits.

Summary of food sources

Fish, poultry, and meats dominate the top 10 protein sources by total grams per serving. In the average U.S. adult diet, meats and poultry contribute about 40% of protein intake, with fish, eggs, and dairy supplying another 30%. These figures reflect dietary patterns, not requirements. Optimal protein intake does not require any animal foods.

Among plant foods, legumes provide the highest concentrations. Several legumes supply 30% or more of the DV in a one-cup serving. A legume-based soup like Italian Navy Bean Soup with Rosemary delivers close to 15 grams per bowl.

Nuts, seeds, and whole grains can all be significant contributors to protein intake. Expect that a serving of any of these three food groups should contain around 10-15% of your daily requirement. One ounce of pumpkin seeds can add 5 grams of protein to your daily meal plan. So can one cup of brown rice.

Vegetables can contain more protein than you might guess. Some categories of vegetable, brassicas and greens, for instance, can contain 5-10% of your protein needs per serving. You’ll be getting over 5 grams of protein from a single cup of spinach or collards, and over 7 grams from a single cup of green peas.

Building a protein-sufficient diet with animal foods is straightforward. Four ounces of chicken or turkey provides about 35 grams; the same amount of most fish and red meats supplies roughly 25 grams. A single serving uses only 8-10% of an 1,800-calorie day, and the remaining whole foods easily cover the 15-25 gram gap.

Let’s instead attempt to build out a diet that meets protein needs using only vegetarian choices. At breakfast, let’s start with 10-minute Energizing Oatmeal. This will start our day with 14 grams of protein, or about 30% of our daily requirement. For lunch, we’ll choose the Fettuccini with Spinach Pesto, to get another 19 grams of protein. For dinner, let’s do Black Bean Chili. Here, we’ll get another 24 grams to round out our day.

That already exceeds the 50-gram DV at only about 1,300 calories. Adding a mid-afternoon snack of 10-minute Peanut Bars (4 grams) and a 10-Minute Fresh Berry Dessert with Yogurt and Chocolate (7 grams) brings the total to 68 grams of plant-based protein without specifically targeting high-protein selections.

Nutrient rating chart

Introduction to nutrient rating system chart

Read more background information and details of our rating system

WHF ranked as quality sources of
protein

Food

Serving
Size

Cals

Amount
(g)

DRI/DV
(%)

Nutrient
Density

World’s
Healthiest
Foods Rating

Tuna

4 oz

147.4

33.06

66

8.1

excellent

Cod

4 oz

96.4

21.24

42

7.9

excellent

Chicken

4 oz

187.1

35.18

70

6.8

very good

Turkey

4 oz

166.7

34.17

68

7.4

very good

Soybeans

1 cup

297.6

28.62

57

3.5

very good

Salmon

4 oz

157.6

26.59

53

6.1

very good

Beef

4 oz

175.0

26.16

52

5.4

very good

Shrimp

4 oz

134.9

25.83

52

6.9

very good

Lamb

4 oz

310.4

25.57

51

3.0

very good

Scallops

4 oz

125.9

23.29

47

6.7

very good

Sardines

3.20 oz

188.7

22.33

45

4.3

very good

Tofu

4 oz

164.4

17.89

36

3.9

very good

Spinach

1 cup

41.4

5.35

11

4.7

very good

Asparagus

1 cup

39.6

4.32

9

3.9

very good

Beet Greens

1 cup

38.9

3.70

7

3.4

very good

Mustard Greens

1 cup

36.4

3.58

7

3.5

very good

Swiss Chard

1 cup

35.0

3.29

7

3.4

very good

Bok Choy

1 cup

20.4

2.65

5

4.7

very good

Tempeh

4 oz

222.3

20.63

41

3.3

good

Lentils

1 cup

229.7

17.86

36

2.8

good

Dried Peas

1 cup

231.3

16.35

33

2.5

good

Pinto Beans

1 cup

244.5

15.41

31

2.3

good

Kidney Beans

1 cup

224.8

15.35

31

2.5

good

Black Beans

1 cup

227.0

15.24

30

2.4

good

Navy Beans

1 cup

254.8

14.98

30

2.1

good

Lima Beans

1 cup

216.2

14.66

29

2.4

good

Garbanzo Beans

1 cup

269.0

14.53

29

1.9

good

Pumpkin Seeds

0.25 cup

180.3

9.75

20

1.9

good

Peanuts

0.25 cup

206.9

9.42

19

1.6

good

Yogurt

1 cup

149.4

8.50

17

2.0

good

Green Peas

1 cup

115.7

7.38

15

2.3

good

Cheese

1 oz

114.2

7.06

14

2.2

good

Oats

0.25 cup

151.7

6.59

13

1.6

good

Eggs

1 each

77.5

6.29

13

2.9

good

Collard Greens

1 cup

62.7

5.15

10

3.0

good

Brussels Sprouts

1 cup

56.2

3.98

8

2.6

good

Cow’s milk

4 oz

74.4

3.84

8

1.9

good

Broccoli

1 cup

54.6

3.71

7

2.4

good

Kale

1 cup

36.4

2.47

5

2.4

good

Green Beans

1 cup

43.8

2.36

5

1.9

good

Cauliflower

1 cup

28.5

2.28

5

2.9

good

Cabbage

1 cup

43.5

2.27

5

1.9

good

Miso

1 TBS

34.2

2.01

4

2.1

good

Soy Sauce

1 TBS

10.8

1.89

4

6.3

good

Sea Vegetables

1 TBS

10.8

1.81

4

6.0

good

Mushrooms, Crimini

1 cup

15.8

1.80

4

4.1

good

Turnip Greens

1 cup

28.8

1.64

3

2.0

good

Summer Squash

1 cup

36.0

1.64

3

1.6

good

Tomatoes

1 cup

32.4

1.58

3

1.8

good

World’s Healthiest
Foods Rating

Rule

excellent

DRI/DV>=75% OR
Density>=7.6 AND DRI/DV>=10%

very good

DRI/DV>=50% OR
Density>=3.4 AND DRI/DV>=5%

good

DRI/DV>=25% OR
Density>=1.5 AND DRI/DV>=2.5%

Impact of cooking, storage and processing

Our steaming, boiling, and healthy sauté cooking methods will not result in any significant protein loss from any of our WHF. Nor will storage of these foods using our recommended approach and suggested time frames. Protein tends to be a stable nutrient within the above context.

Proteins and their amino acids can interact with sugars under certain circumstances to form other compounds. Many of these chemical reactions - for example, the Maillard reaction - are actually very complicated in terms of their biochemistry and have yet to be fully researched. One possible result of protein-sugar interactions involves formation of molecules called advanced glycation end-products, or AGES. When excessive numbers of AGEs are formed in the body, we know that they can contribute to increased risk of chronic diseases including atherosclerosis, osteoarthritis, cataracts, neurodegenerative diseases, and cataracts. Relatively recent research indicates that AGEs can not only get preformed in food but can get absorbed up into our body in significant amounts and contribute to the “pool” of AGEs that have already been formed as a result of our own metabolism. The cooking methods that appear mostly likely to increase AGE formation in protein-rich foods including grilling, searing, and frying. Formation of AGEs from protein-sugar interactions is one of the reasons we avoid these cooking methods at WHF. A second area of concern in protein cooking involves possible formation of acrylamides. Potato chips, french fries, and grain-based coffee substitutes are processed foods in which acrylamide formation has been most extensively studied. You can find many more details in our Q & A, What is acrylamide and how is it involved with food and health?

Finally, we would like to note that caramelization of food (as exemplified by the heating and browing of onions) is not a protein-based chemical reaction but a reaction only involving food sugars and is not the same as the above-described AGE formation and acrylamide formation processes.

Risk of dietary deficiency

Daily consumption of animal foods (meat, fish, dairy, eggs) almost certainly meets or exceeds the 50-gram DV for protein.

However, you don’t need to eat animal foods much or even at all to meet the DV. . An average American lacto-ovo-vegetarian (a vegetarian who eats dairy and eggs) eats 89 grams of protein per day, almost twice the Daily Value (DV) of 50 grams. Even when we subtract the contributions of dairy and eggs, we still see about 60 grams of protein from purely plant sources.

It would actually be quite difficult to design a whole foods diet that provided less than 10% of its calories from protein. An 1,800-calorie whole foods diet consisting exclusively of fruit, for example, would typically still provide at least 40 grams of protein. An 1,800 calorie whole foods diet consisting exclusively of broccoli would provide 121 grams! Of course, we would never recommend either of these approaches to a meal plan, but they are helpful in demonstrating just how difficult it is to come up with a highly protein deficiency diet based on a whole foods approach to eating.

More up in the air is the question of health benefits from a meal plan that greatly exceeds the protein DV of 50 grams. As discussed earlier, we have seen the develop of a research trend that suggests possible advantages to a meal plan in which protein represents 15-25% of total calories (67-112 grams) instead of the 11% level represented by 50 grams. We definitely look forward to more research in this area.

Other circumstances that might contribute to deficiency

Disordered eating patterns can lead to protein-energy malnutrition, which can often become quite serious. As many as 24 million Americans suffer from one or more eating disorders. These disorders are often undiagnosed, and only one in ten people receives the medical treatment these conditions often require.

There are some severe disease states that cause an increase in protein breakdown. In these conditions, it may be difficult or even impossible to eat enough dietary protein to offset the loss.

While many sources recommend it, the National Academy of Sciences does not recommend a different protein requirement based on level of physical activity. The American College of Sports Medicine, however, does recommend at least paying attention to protein intake to make sure that needs are met during times of intensive training. You will find this issue discussed in more detail in our earlier section entitled “Other Potential Health Benefits” in our Role in Health Support section.

Relationship with other nutrients

As your protein intake goes up, so can your urinary loss of calcium. This phenomenon is related to the use of calcium as a buffer when proteins or their amino acids are primarily acidic. However, from a research standpoint, the jury is out on exactly how this natural physiologic process relates to any potential health risks. (For example, too much extraction of calcium from our bones could increase our risk of osteoporosis.) We expect future studies to help clarify the nature of these protein-and-calcium relationships. As mentioned earlier in our Impact of Cooking, Storage, and Processing section, proteins and amino acids can react with certain types of sugars to produce advanced glycosylation end-products (AGEs) and other compounds (including acrylamides). Please see that earlier section for more detail.

Risk of dietary toxicity

The National Academy of Sciences (NAS) established an Acceptable Macronutrient Distribution Ranges (AMDRs) for protein in 2005. Important, the NAS did not consider these ranges to be Dietary Reference Intake guidelines that established specific upper (or lower) limits for protein intake. Instead, these AMDRs were viewed as general guidelines that could be considered helpful in potentially lowering disease risk. These 2005 AMDRs for protein were established as follows:

• Adults: 10-35% of total calories
• Children 1-3 years: 5-20% of total calories
• Children and Teens 4-18 years: 10-30% of total calories

Let’s take the adult guidelines of 10-35% and translate these percentages into more practical terms. And let’s start out with the high end guideline for protein intake of 35% total calories. Here are the grams of protein that correspond to 35% of total calories at different calorie levels:

• 131 grams of protein in a 1,500-calorie diet
• 157 grams of protein in an 1,800-calorie diet
• 175 grams of protein in a 2,000-calorie diet
• 219 grams of protein in a 2,500-calorie diet

Now let’s look at the low end of this protein guideline (10% of total calories). Here are the grams of protein that correspond to 10% of total calories at different calorie levels:

• 38 grams of protein in a 1,500-calorie diet
• 45 grams of protein in an 1,800-calorie diet
• 50 grams of protein in a 2,000-calorie diet
• 63 grams of protein in a 2,500-calorie diet

Since the Daily Value (DV) for protein is based on a 2,000-calorie meal plan, you can see how this lower limit of the AMDR for protein hits exactly at that 10% level. However, in this section on Risk of Dietary Toxicity, it is the high end of the AMDR that we are most concerned about, and you can see how this high end very roughly corresponds to protein intake in the 150-200 gram per day range.

It is very hard in practice to go beyond this level from whole foods! Whole foods set a natural limit on the total amount of protein that you can consume within any fixed amount of calories, because no whole food consists of pure protein. Instead, protein-containing whole foods also contain varying amounts of fat, and fat is a nutrient that contains more than double the calories of protein. So as a result, all whole foods end up increasing their calories at a quicker rate than their grams of protein. These ratios between protein, fat, and calories in whole foods enable you to stay within the AMDR guidelines in virtually any balanced meal plan.

Disease checklist

• Anorexia and other eating disorders
• Malabsorption disorders
• Heavy exercise
• Weight loss
• Diabetes prevention
• Immunodeficiency problems
• Problems with insulin resistance

Public health recommendations

In 2005, the National Academy of Sciences established a set of Dietary Reference Intakes (DRIs) for protein that included age and gender specific Recommended Dietary Allowances (RDAs) for protein. Note that the recommendations for infants from 0-6 months of age were established as Adequate Intake (AI) levels. The complete set of DRIs is as follows: .

• 0-6 months: 9.1 grams
• 6-12 months: 11 grams
• 1-3 years: 13 grams
• 4-8 years: 19 grams
• 9-13 years: 34 grams
• 14-18 years, female: 46 grams
• 14-18 years, male: 52 grams
• 19+ years, female: 46 grams
• 19+ grams, male: 56 grams
• Pregnant women: 71 grams
• Lactating women: 71 grams

Note that for adults, these RDA assume an average body weight of 70 kg (or 154 lbs) for a male and 57.5 kg (or 126 lbs) for a female. For people significantly different from these target weights, you may choose to include 0.8 grams of dietary protein per kilogram (about 2.2 pounds) of body weight.

In 2005 the National Academy of Sciences (NAS) also issued a set of Acceptable Macronutrient Distribution Ranges (AMDRs) for protein as a percentage of total calories. They recommend keeping protein calories between 5 and 20% of calorie total in ages 1-3 years, 10 to 30% in children ages 4-18, and 10-35% in adults. The NAS did not consider these AMDRs to be part of the Dietary Reference Intakes (DRIs), but rather very general guidelines with the potential to lower risk of health problems. In our Risk of Dietary Deficiency section, you can find practical details about these AMDR guidelines.

The Daily Value (DV) recommendation for protein is 50 grams per day for adults. This is the standard you will see listed on food labels. It is also the standard that we have adopted at WHF as our recommended minimal amount of daily protein intake.

What can high-protein foods do for you?

• Keep your immune system functioning properly
• Maintain healthy skin, hair and nails
• Help your body produce enzymes

What events can indicate a need for more high-protein foods?

• Muscle wasting
• Weight loss
• Fatigue and weakness
• Frequent infections
• Severe edema (fluid retention)
• Slow growth and development in children

Excellent sources of protein include turkey, tuna, shrimp, and cod.

WHF rich in
protein

FoodCalsDRI/DV

 Chicken18770.3%

 Turkey16768.3%

 Tuna14766.1%

 Soybeans29857.2%

 Salmon15853.1%

 Beef13352.3%

 Shrimp13551.6%

 Lamb35051.1%

 Scallops12646.5%

 Sardines18944.6%

For serving size for specific foods see the Nutrient Rating Chart.

• Description

• Function

• Deficiency Symptoms

• Toxicity Symptoms

• Cooking, storage and processing

• Factors that affect function

• Nutrient interaction

• Health conditions

• Food Sources

• Nutrient Rating Chart

• Public Health Recommendations

• References

Description

What is protein?

Protein was the first substance to be recognized as a vital part of living tissue. In fact, the word protein comes from the Greek word proteos, which means “primary” or “taking first place,” indicating the importance of this nutrient in the function of the body. Accounting for 20 percent of our body weight, proteins perform a wide variety of functions throughout the body as vital components of body tissues, enzymes, and immune cells.

Proteins are complex molecules comprised of a combination of different amino acids, which are compounds that contain carbon, oxygen, hydrogen, nitrogen and sometimes sulfur. Amino acids link together in specific numbers and unique combinations to make each different protein.

Protein is an essential component of the diet, because it provides the amino acids that the body needs to synthesize its own proteins. In traditional nutrition textbooks, there have always been two types of amino acids: essential amino acids and non-essential amino acids. Essential amino acids have been defined as those amino acids that our body cannot synthesize on its own. Essential amino acids must therefore be obtained from our diet. As traditionally defined, the eight essential amino acids are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. There has been ongoing debate over the status of a ninth amino acid, histidine. Because the body appears routinely unable to make sufficient amounts of histidine during certain periods of development, this amino acid has sometimes been classified as essential and sometimes not.

Nonessential amino acids have traditionally been defined as those that the body can manufacture on its own. It is therefore not necessary to obtain these amino acids from the diet. As traditionally defined, the nonessential amino acids include glutamate, alanine, aspartate, and glutamine, as well as arginine, proline, serine, tyrosine, cysteine, taurine, and glycine.

This traditional separation of amino acids into the categories of “essential” and “non-essential” seems unrealistic. While it is true that the human body has the potential to manufacture all non-essential amino acids, this potential is not the same as actually making them. There are many circumstances in which the body cannot make nearly enough of the non-essential amino acids it needs. For example, when a person is exposed to large amounts of environmental toxins and pollutants, the amount of glycine (a non-essential amino acid) made by the body may be far from adequate. For this reason, it may be more constructive to think about all non-essential amino acids as “conditionally essential.” This classification would point out that under certain physiological circumstances, the body would unable to manufacture enough of these amino acids and they would have to be obtained through diet (or supplementation). This concept of “conditionally essential amino acids” tells us that all of the amino acids can be equally important when it comes to our diet, and that it’s worthwhile for us to pay attention to all amino acids when thinking about the nourishment we get from our food.

The body is only able to make the proteins it needs when there are sufficient quantities of all the necessary amino acids in the so-called “amino acid pool.” If we are deficient in essential amino acids, the body will be unable to make proteins and will have to break down muscle proteins to obtain the amino acids it needs.

As a result, it is imperative that our daily intake of food contains each of the essential amino acids, which is easily accomplished by eating a variety of vegetables, beans, whole grains, nuts, seeds, and meat and animal products if desired.

How it functions

What is the function of protein?

Protein, providing 4 calories per gram, is an important source of energy for the body, when carbohydrates and fats are not available. In addition to using protein to generate energy for cellular function whenever necessary, the body uses the amino acids contained in the protein we eat to manufacture its own proteins. The proteins synthesized by the body perform a variety of important physiological functions:

• Production and maintenance of structural proteins: The body manufactures several structural proteins, such as myosin, actin, collagen, elastin, and keratin, that maintain the strength and integrity of muscles, connective tissues (ligaments and tendons), hair, skin, and nails.
• Production of enzymes and hormones: All of the enzymes, which are compounds that catalyze chemical reactions in the body, are made from protein. In addition, the hormones involved in blood sugar regulation (insulin and glucagon) as well as the thyroid hormones are synthesized from proteins.
• Production of transport proteins and lipoproteins: Certain proteins are used by the body to carry various substances to body tissues. These transport proteins include hemoglobin (carries oxygen), transferrin (carries iron), ceruloplasmin (carries copper), retinol-binding protein (carries vitamin A), albumin and transthyretin (both carry other proteins). Lipoproteins participate in the transportation of fat and cholesterol.
• Production of antibodies: Antibodies, which are proteins, play an important role in the immune system by attaching to antigens (viruses, bacteria, or other foreign invaders), thereby inactivating the antigens and making them more visible to the immune cells (called macrophages) that destroy antigens.
• Maintenance of proper fluid balance: Proteins participate in the maintenance of osmotic pressure, which controls the amount of water that is found inside of cells.
• Maintenance of proper acid-base balance: Due to their ability to combine with both acidic and basic substances, proteins help to maintain the normal acid-base balance in the body.

Deficiency symptoms

What are deficiency symptoms for protein?

Both adults and children can live healthfully on a low intake of protein, assuming they eat a sufficient amount of calories and all of the essential amino acids are present in the diet. As a result, the symptoms of protein deficiency are most often seen in impoverished people who have limited access to food.

Protein-energy malnutrition, caused by low intake of both protein and calories, is especially common in children in underdeveloped nations, because children require more protein per kilogram of body weight than adults to support the rapid growth and development that occurs during childhood.

According to the World Health Organization, approximately 300 million children throughout the world suffer from growth retardation due to protein-energy malnutrition. Additionally, children with protein-energy malnutrition have a 40% mortality rate, due to increased susceptibility to infections.

In developed countries, protein-energy malnutrition is most likely to affect people who have suffered severe physical trauma that increases protein needs (for example, extensive skin burns) or those who have a medical condition or psychological problem that impacts their desire or ability to eat. The elderly are also at risk for protein-energy malnutrition.

There are two types of protein-energy malnutrition: marasmus and kwashiorkor. Marasmus is a state of semi-starvation that can occur in people of all ages who have limited access to food, but is most common in non-breastfed children given diluted infant formula. The symptoms of marasmus include weight loss, muscle wasting, loss of visible fat stores, weakness and fatigue, and frequent infections due to diminished activity of the immune system.

Kwashiorkor, a Ghanian word for “the evil spirit that infects the child”, was first described in 1933 and typically occurs in children younger than 4 years old fed diets high in carbohydrates with little or no protein. Symptoms of kwashiorkor include muscle wasting, edema (fluid retention), and an enlarged and fatty liver, with the preservation of visible fat stores.

Because meat and dairy foods are a primary source of protein in the American diet, many nutritionists caution that those following a vegetarian or vegan diet may be at risk for protein deficiency. However, vegetarians and vegans who eat a variety of vegetables, grains and legumes can easily meet or exceed current protein requirements.

Toxicity symptoms

What are toxicity symptoms for protein?

Excessive intake of protein over many years may lead to kidney problems and/or accelerated bone loss eventually leading to osteoporosis. Due to the lack of a dose-response relationship at higher levels of protein intake, the National Academy of Sciences (NAS) decided not to set a Tolerable Upper Limit (UL) for protein in 2002. However, the NAS did note that the building blocks of protein, called amino acids, should not be consumed in amounts significantly above the amounts found in food.

Because the kidneys play a primary role in protein metabolism, individuals with end-stage kidney disease must carefully monitor their intake of protein.

Factors that affect function

What factors might contribute to a deficiency of protein?

Protein digestion and metabolism involves the stomach, pancreas and liver. Hydrochloric acid, secreted by the stomach, is necessary for the initial digestion of protein. Pancreatic enzymes participate in the breakdown of protein. And the liver controls amino acid metabolism.

Consequently, any medical condition that comprises the function of the stomach, pancreas, or liver may negatively impact protein status. In addition, the ability of the body to manufacture non-essential amino acids may be hampered with inadequate intake of vitamin B6.

Individuals with bacterial or viral infections and those who have experienced severe physical trauma use up their protein stores rapidly, and may need to increase their intake of protein.

Nutrient interactions

How do other nutrients interact with protein?

Various proteins bind and carry certain vitamins and minerals including iron, copper, calcium, vitamin A, and vitamin D. As a result, inadequate protein intake may impair the function of these nutrients.

Health conditions

What health conditions require special emphasis on protein?

Although adequate protein intake is necessary for health, protein is not often used therapeutically. However, high dietary intake of protein is beneficial for people who have experienced severe physical trauma and may be helpful for athletes. Additionally, several individual amino acids including glutamine, lysine, phenylalanine, tyrosine, arginine, and cysteine are commonly used therapeutically.

Food sources

What foods provide protein?

Excellent sources of protein include turkey, tuna, shrimp, turkey, and cod.

Very good sources of protein include halibut, salmon, scallops, sardines, chicken, lamb, grass-fed beef, calf’s liver, spinach, tofu, mustard greens, asparagus, soybeans, salmon, and cheese.

Good sources of protein include crimini mushrooms, eggs, summer squash,collard greens, cauliflower and many legumes including lentils, split peas, kidney beans, black beans, pinto beans and garbanzo beans.

When discussing food sources of protein, nutritionists often speak in terms of “complete” and “incomplete” proteins. Foods that provide complete protein are those that include all of the essential amino acid, while foods that provide some or none of the essential amino acids are said to be incomplete.

Eggs, dairy foods, meat, fish and poultry are typically considered to be complete proteins. Vegetarians, and especially vegans, often do not have a source of complete protein in their diets, but can easily obtain all of the essential amino acids by eating a variety of beans, grains, nuts, seeds, and vegetables.

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