by Tandis Bishop, RD
Probably no component of food has been so misunderstood, and so radically misinterpreted, as protein. When we talk about vegetarianism, usually the biggest concern people have is "How can I get enough protein?" This myth is finally becoming dissolved as leading health organizations are highlighting the significance of plant-based proteins as opposed to the detrimental health hazards of animal-protein often excess in the average American diet. You will see that it is almost impossible to be protein deficient on a well-balanced, calorie-adequate vegetarian diet.
Plant-based foods as key to healthy lifestyle are emphasized in guidelines by The American Heart Association, American Cancer Society, American Diabetes Association, The American Institute for Cancer Research, and many other health organizations. In fact, the new USDA MyPlate food guide is about 75% plant-based.
What is protein?
Protein is an essential nutrient involved in virtually all cell functions. In the body, protein is required for structural support, and the maintenance and repair of tissues. It is also the basic component for immunity, most hormones, and all enzymes, among other functions. In food, proteins are made from chains of 20 different amino acids, the building blocks of protein. Our bodies can only produce 11 of these amino acids. The 9 "essential" amino acids, which cannot be made by the body must be obtained from food. A diet with a variety of whole grains, legumes, and vegetables can provide all the essential amino acids to meet our bodies requirement.
How much protein do we need?
The Recommended Dietary Allowance (RDA) for protein for adults is 0.8 grams per kilograms of weight.1 To calculate your individual daily protein needs, use the following calculation: Body weight (in pounds) X 0.36 = recommended protein intake (in grams) For example, the daily protein requirement is about 60 grams for a 170 lb male, and about 47 grams of protein for a female that weighs about 130 lbs. In addition, the RDA recommendation includes a large safety factor for most people. Protein needs are increased for women who are pregnant or nursing which can easily be met with their higher caloric intake requirements. Protein deficiency is extremely unlikely when daily calorie needs are met by a variety of whole grains, vegetables, beans, lentils, tofu, nuts, seeds, and dairy products.
Plants are rich in protein.
Plants are by nature rich sources of protein as they are made up of structural cells, hormones and enzymes. In fact, plants are so rich in protein that they meet the needs of the earth’s largest animals: elephants, giraffes, hippopotamuses, gorillas, cows, and horses. If these large animals with big, strong muscles can get adequate protein from plants, then so can we.2Table 1:3 Protein Content of Selected Plant Foods
|Seitan (seasoned wheat gluten)||3 ounces||31|
|Soybeans, cooked||1 cup||29|
|Lentils, cooked||1 cup||18|
|Black beans, cooked||1 cup||15|
|Kidney beans, cooked||1 cup||13|
|Veggie burger||1 patty||13|
|Chickpeas, cooked||1 cup||12|
|Veggie baked beans||1 cup||12|
|Pinto beans, cooked||1 cup||12|
|Black-eyed peas, cooked||1 cup||11|
|Tofu, firm||4 ounces||11|
|Lima beans, cooked||1 cup||10|
|Quinoa, cooked||1 cup||9|
|Tofu, regular||4 ounces||9|
|Bagel||1 med (3 oz.)||9|
|Peas, cooked||1 cup||9|
|Textured Vegetable Protein (TVP), cooked||1/2 cup||8|
|Peanut butter||2 Tbsp||8|
|Veggie dog||1 link||8|
|Spaghetti, cooked||1 cup||8|
|Soy milk, commercial, plain||1 cup||7|
|Soy yogurt, plain||6 ounces||6|
|Bulgur, cooked||1 cup||6|
|Sunflower seeds||1/4 cup||6|
|Whole wheat bread||2 slices||5|
|Almond butter||2 Tbsp||5|
|Brown rice, cooked||1 cup||5|
|Spinach, cooked||1 cup||5|
|Broccoli, cooked||1 cup||4|
|Potato||1 med (6 oz.)||4|
Table 2:3 Sample menu below shows how easy it is to meet protein needs on a vegetarian diet. Note that sample menu only lists high-protein foods that would be included in a balanced diet. Additional food should be added to these menus to provide adequate calories and to meet requirements for nutrients besides protein.
|Meal||Food/portion Size||Protein (grams)|
|Breakfast||1 cup oatmeal||6|
|1 cup soymilk or low-fat milk||7-8|
|Lunch||2 slices whole wheat bread||5|
|1 cup Vegetarian baked beans||12|
|Dinner||5 oz firm tofu||11|
|1 cup cooked broccoli||4|
|1 cup cooked brown rice||5|
|Snack||2 Tbsp peanut butter||8|
Protein Recommendation for 170 lb Male [based on 0.8 gram of protein per kilogram body weight for 77 kilogram (170 pound)]: 61 grams
|Meal||Food/portion Size||Protein (grams)|
|Breakfast||1 whole wheat bagel||9|
|2 Tbsp almond butter||5|
|Lunch||6 oz. low-fat yogurt or soy yogurt||6|
|1 baked potato||4|
|Dinner||½ cup cooked lentils||9|
|1 cup cooked quinoa||9|
|Snack||1/4 cup cashews||5|
Protein Recommendation for 130 lb Female [based on 0.8 gram of protein per kilogram body weight for 59 kilogram (130 pound)]: 47 grams
Additional food should be added to these menus to provide adequate calories and to meet requirements for nutrients besides protein.
The main problem with protein is excess animal protein.
The average American consumes close to 100 grams of protein a day4. This is almost double the amount of protein that is needed. Contrary to popular belief, excess protein cannot be stored. Any excess protein is either converted to sugar and burned as energy, or converted into fat with its waste products eliminated through the kidneys. When protein is metabolized, some toxic substances such as urea are created during the breakdown process because of the nitrogen content. Sulfur, a by-product of the breakdown of amino acids such as methionine and cysteine also must be eliminated and is turned into sulfuric acid. These then must be eliminated through the kidneys. Therefore, one of the adverse side effects of high intake of protein is that a tremendous strain is put on the kidneys to eliminate the waste byproducts5. However, the risks associated with all protein are reduced when consuming plant proteins because the concentration of protein from plant sources is less than the concentration from animal sources.
High protein intake and osteoporosis.
When high amounts of protein (especially sulfur-containing amino acids) are consumed, buffers (such as calcium) from the bones are released in order to neutralize the acids. This process can eventually result in the dissolving and weakening of the bones, known as osteoporosis.6 The concentration of protein is much less for plants than animal products. Thus, plant-based foods are a better source of calcium than animal sources in reducing the risk for osteoporosis. Examples of plant sources high in calcium are dark green leafy vegetables, broccoli, seaweed and tofu. In addition, fruits and vegetables have an alkalizing effect on the body when they act as a buffer to help prevent osteoporosis and other acid-based disorders7.
Plant-based proteins: a healthier choice.
In general, plant proteins are healthier because of the other food components that come with them. All plant-based proteins are accompanied by fiber, versus animal sources of protein which have essentially no fiber. Plant-proteins are packaged along with cancer-fighting phytochemicals. They also tend to be low in fat and have zero cholesterol. As a general guideline, aim to have your daily intake of whole grains, vegetables, and legumes to easily meet your protein needs. Dairy products, although not plant-based, also provide significant amount of protein and can be a part of a balanced vegetarian diet when consumed in moderation. Veggie meats or meat substitutes are also great sources of protein that can be added to your daily diet.
- Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 2010. USDA, 2010. Web, September 5 2011 http://www.cnpp.usda.gov/DGAs2010-DGACReport.htm
- McDougall JA. When Friends Ask: Where Do You Get Your Protein? April 2007. Available at: http://www.drmcdougall.com/misc/2007nl/apr/dairy.htm
- "Protein in the Vegan Diet." The Vegetarian Resource Group. http://www.vrg.org/nutrition/protein.htm (Accessed Dec. 13, 2011)
- Fulgoni, III, L.V., Current protein intake in America: analysis of the National Health and Nutrition Examination Survey, 2003–2004. Am. J. of Clinical Nutrition, May 2008, 87(5): 1554S-1557S
- Knight EL, Stampfer MJ, Hankinson SE, et al. The impact of protein intake on renal function decline in women with normal renal function or mild insufficiency. Ann Intern Med 2003;138:460-7.
- Shintani TT. Eat More Weigh Less Diet. Kamuela,HI: Halpax. 1993
- S. A Lanham-New. Fruit and vegetables: the unexpected natural answer to the question of osteoporosis prevention? Am. J. Clinical Nutrition, June 1, 2006; 83(6): 1254 - 1255