We get protein from both animal and plant foods. During the Stone Age, our ancestors got most of their protein from plants. Much later, our ancestors began eating meat. Today, most of the protein we eat comes from animal products.

Table of Contents for Protein Introduction Food Guide Pyramid Review What You Will Learn What is Protein What Proteins Do Building Blocks Called Amino Acids Amino Acids in Protein Foods That Give Proteins Nutrition Labeling What Counts as a Serving? How Much Protein Do You Need? Summary Review questions Back to Nutrition Curriculum Lessons

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Amino Acids in Protein

Proteins are made up of amino acids. The kinds and amounts of amino acids in a protein determine its nutritive value. We get protein from both animal and plant foods. During the Stone Age, our ancestors got most of their protein from plants. Much later, our ancestors began eating meat. Today, most of the protein we eat comes from animal products.

Animal proteins, such as animal muscle (meats), milk and eggs, can supply all of the amino acids in about the same proportions in which they are needed by the body. These are rated as having a high nutritive value. Animal proteins are considered high-quality proteins or complete proteins. They can support body growth and maintenance because they contain all of the essential amino acids in sufficient amounts.

Plant proteins are usually thought of as low-quality proteins or incomplete proteins. This means that single plant proteins cannot easily support body growth and maintenance because each protein lacks adequate amounts of one or more essential amino acids. If you eat foods that contain low-quality protein or foods that do not provide an appropriate balance of all nine essential amino acids, you will also need to eat some high-quality protein to get enough of the essential amino acids needed for protein synthesis. Proteins from plant foods such as fruits, vegetables, grains and nuts supply important amounts of many amino acids, but they do not supply as good an assortment as animal proteins do. Their nutritive value is lower. The proteins from some of the legumes, especially soybeans and chickpeas, are almost as good as those from animal sources. Grains, nuts and legumes are more concentrated sources of amino acids than fruit and vegetables.

To have the nutritive value of the mixture of proteins in our diets rate high means that we need only a portion of the protein to come from animal sources. So, when we eat a meal of red beans and rice, we need a glass of skim milk to round out the protein that we need. We do not need to have ham or other meat with the red beans, too.

As a rule, since Americans eat foods with proteins of high nutritive value regularly, they don't need to be concerned about the adequacy of the amino acids they get. Rather, the concern is with eating too much protein from animal sources, which generally are more expensive and are higher in saturated fats than plant sources.Since meats contribute so much saturated fat to our diet, we need to select meat that is lower in fat.

Foods That Give Proteins

Food proteins from animal sources are generally of higher quality than proteins from plant sources. Meat, poultry, fish, eggs, milk, cheese and yogurt provide all nine essential amino acids. Because of that, they are often referred to as complete proteins.

Legumes such as beans and peas, seeds and nuts supply protein, also. In smaller amounts, so do grain products and many vegetables. Plant proteins, except soy, lack one or more essential amino acids. However, when you eat a variety of foods, you get all the amino acids your body needs. Eat a variety of plant foods - legumes, nuts, seeds, grains, vegetables and fruits and enough calories throughout the day. Whatever amino acid one food lacks can come from other foods you eat during the day.

Food tip: What is the most nutrient-dense source of protein? Water-packed tuna, which has over 80% of calories as protein, followed by chicken breast without skin.

If you eat a plant protein that has one or more limiting amino acids, getting that amino acid from eating another food or foods can make up for the shortfall in the first. This is called complementing or eating together foods whose amino acids are collectively in proportion with what your body needs, although individually they are not. Some examples of good pairs of plant proteins that together give all of the amino acids needed are as follows:

• Legumes (starchy beans, peas and lentils) paired with grains
• Peanut butter sandwich
• Red beans and rice
• Baked beans and wheat bread
• Lima bean and rice casserole
• Bean burrito (bean filling in corn tortilla)
• Split pea soup and rye bread
• Bean chili and wheat toast
• Legumes (starchy beans, peas and lentils) paired with nuts and seeds
• Snack mix of roasted soybeans, nuts and seeds
• Hummus (ground chickpeas and sesame seeds)
• Tofu dishes with sesame seeds

Power Buy: Legumes

Legumes are plants with seed pods that contain one row of seeds. They include garden peas, green beans, red beans, lima beans, pinto beans, black-eyed peas, garbanzo beans, lentils and soybeans. Dried varieties of the seeds give an impressive contribution to the protein, vitamin, mineral and dietary fiber content of a meal.

Legumes are a power buy. Legumes are a very inexpensive source of protein that can meet your protein needs. A bonus of legumes is that they contain many other nutrients.

Although legumes are a source of incomplete protein, combine them with rice, corn or other grains or with small amounts of complete protein in meat, eggs or cheese to provide a high-quality protein balance.

Legumes are versatile. They can be used in many ways. You can make tasty soups, salads, casseroles, dips and chili with legumes. They can even be mashed and combined with other ingredients for a sandwich filling. Try to include legumes in your meals at least two to three times a week for maximum health benefits.

Tip: Problems with intestinal gas when eating legumes?

If you have avoided eating legumes because they may give you intestinal gas, there are some things you can do to help avoid this problem. When you first add beans to your diet, they may cause intestinal gas. Lima beans, split peas and lentils are less likely to do so than the others, so start with them. Eat small amounts of legumes at first and give your gastro-intestinal tract a few weeks to adjust.

An enzyme preparation called Beano is also available. You can buy it in the store. Taken right before a meal, it helps digest the indigestible carbohydrates in beans that contribute to intestinal gas.

Cooking tip:

Most legumes except lentils need to be softened before cooking. Soak them overnight. Or, boil for two minutes, uncovered. Remove from heat, cover, and let stand one hour. Discard the soaking water. This liquid is loaded with indigestible carbohydrates. Then add seasoning and fresh water for cooking. Keep in mind that dried beans double or triple in volume as they cook.