People who follow a vegetarian diet constantly hear the question, "How do you get enough protein?" Guidelines for appropriate protein consumption have changed in recent years and nutritionists are now less likely to claim that a vegetarian diet is by nature a protein-deficient diet. However, a healthy vegetarian diet is necessary to ensure that an individual does get sufficient protein.
Essential Amino Acids
All proteins are made up of building blocks known as amino acids. Our bodies can produce some of these substances, but others called essential amino acids must be consumed. While meat and other animal-based foods possess a full profile of essential amino acids, most plant-based foods are deficient in one or more aminos and thus not considered complete protein sources. Vegetarians and especially vegans need a combination of plant-based protein sources to get all the essential amino acids.
Protein Requirements
According to the USDA, adult women need 46 grams of protein a day while adult men need 56 grams. This is based on the recommended minimum amount of 0.8 gram of protein per kg of weight or 0.36 gram per pound. Although many people, and in particular vegetarians, worry about consuming sufficient protein health problems can also result from excess protein intake. According to the Physicians Committee for Responsible Medicine (PCRM), high protein intake can contribute to osteoporosis, kidney problems and some types of cancer. The Vegetarian Resource Group recommends that vegetarians eat 0.8-1.0 grams of protein per kg of weight, and the Vegetarian Society recommends that no one consume more than twice the recommended intake level.
Protein Sources
Vegetarian sources of protein include legumes, grains, nuts and seeds. Soy is considered a complete protein source possessing all the essential amino acids. Quinoa and amaranth are particularly high in protein, as are beans and legumes and blue-green algae. Lacto-ovo vegetarians--those who eat dairy and egg products--can also get protein from animal-sourced products such as cheese, eggs, milk and yogurt. According to the Vegetarian Resource Group, a cup of soybeans has 29 grams of protein, a cup of lentils has 18 grams of protein and a 4-oz. serving of tofu has 11 grams of protein. Even a cup of spinach has 5 grams of protein, and a cup of oatmeal has 6 grams.
Protein Combining
In the past, nutritionists often counseled vegetarians to combine several protein sources in each meal to ensure a full profile of essential amino acids. Now, however, the consensus is that consuming a variety of protein sources throughout the day is sufficient to meet a vegetarian's complete protein needs. The American Dietetic Association states in a position paper on vegetarian diets 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."
Deficiency Risk
Vegetarians do not necessarily eat a healthy diet, so protein deficiency is still a risk despite the abundance of protein-rich vegetarian and vegan foods. Individuals who do not eat enough food to meet their energy needs due to illness or dieting are likely to be deficient in protein, as are those who consume primarily junk food and protein-poor foods such as fruit, sugar, fat and alcohol. Someone who relies only on a single source of protein or very few sources may also become deficient in one or more essential amino acids. Consumption of a variety of protein-rich grains, legumes and nuts is necessary to ensure a healthful vegetarian diet, especially for strict vegans.
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