Vegetarians eat lots of leafy greens -- but where's the protein? See more pictures of vegetables.“Vegetarians eat lots of leafy greens — but where’s the protein? See more pictures of vegetables.Andrey Popov | Dreamstime

You may have heard of the Atkins diet, a high-proteindiet that started a trend and threw nutritionists and the media into something of a protein obsession. Is protein really that important? And what about vegetarians? If you’re not eating meat, are you missing something important in your diet?

Proteins help make up all cells in the human body, from your hair to your blood transport molecules. A person deficient in protein can’t grow, loses muscle mass and has weakened immune, heart and respiratory systems.

Proteins are organic compounds made of amino acids. The body can make some of its own amino acids — these are called nonessential amino acids. The amino acids the body can’t make on its own are called essential amino acids. People have to get these proteins from the food they eat.

If a food contains enough essential amino acids, it’s called a complete protein. Meat, fish, shellfish, eggs, milk and soy products are complete proteins. If the protein in a food doesn’t have all the essential acids, it’s an incomplete protein. Fruits, grains and vegetables are incomplete proteins.

There are different kinds of vegetarian diets. Vegans are the strictest kind of vegetarian — they eat only plant products. Lacto-vegetarians allow dairy products, and lacto-ovo-vegetarians allow eggs as well as dairy products. People who abstain from red meat but who still may eat chicken or fish are called semi-vegetarians or partial vegetarians.

Pick Your Protein

Tofu, a soy product, is an excellent source of complete protein.“Tofu, a soy product, is an excellent source of complete protein.Voon Nam Fook | ­

According to the USDA, the key to a healthy vegetarian diet is variety. In the past, some nutritionists advised a concept called complementary proteins. According to this concept, a vegetarian needs to combine different protein sources in the same meal (pairing rice with beans, for example) depending on the foods’ amino acid makeup. This concept created many a headache for vegetarians — figuring out which food contained leucine and which had the requisite lysine required a chart and some calculations. Today, nutritionists and government agencies say that it’s important to vary sources of protein, but it isn’t necessary to do so in the same meal.

Vegetarians on the market for non-animal protein have a huge variety of choices. Legumes like lentils and peas, whole grains, and seeds and nuts are all good sources of protein. Soy protein is just as complete as animal protein. Tofu, made from coagulated soy milk, is extremely high in protein and available in a variety of forms and flavors. TVP (textured vegetable protein) is a dried soy flour product that can be used as a meat substitute. Most “mock” meats are made from seitan, or wheat gluten, which is known for its versatility in recipes. It’s good to stick to low-fat protein sources instead of trying to replace meat with something high in fat, like cheese. A varied diet is important for everyone, not just vegetarians or vegans.

According to the American Heart Association, most Americans exceed their protein requirement [source: American Heart Association]. Meat is high in protein, but can also be in high in fats, especially saturated fat. Eating too much meat can actually lead to coronary heart disease and other diseases, like diabetes. Diets high in protein can also lead to kidney problems. Following a high-protein fad diet that eliminates or severely reduces carbohydrate intake can also leach calcium from the bones. Vegetarian or not, everyone should eat a balanced diet.

For more information about vegetarians, proteins and related topics, check out the links on the next page.

Lots More Information

Related HowStuffWorks Articles

  • How Food Works
  • How Vegetarians Work
  • How Vegans Work
  • How Freegans Work
  • How Dieting Works
  • How Diet Pills Work
  • How can a diet pill make you feel full?
  • How the Atkins Diet Works
  • How Fats Work
  • Would a fat tax save lives?
  • How Calories Work
  • How Cholesterol Works
  • Vegetarian Recipes

More Great Links

  • MyPyramid Personal Eating Plan
  • Vegetarian Resource Group


  • American Heart Association.
  • USDA
  • Mayo Clinic
  • Harvard School of Public Health


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