Protein is an essential nutrient for maintaining lean muscle mass, fighting infections and allowing vital reactions to occur in your body. Amino acids are the building blocks of proteins, but not all dietary proteins provide methionine and lysine. To prevent deficiencies, it is important to know which foods are sources of these two amino acids.
Meat, Poultry and Seafood
Beef, lamb, chicken, turkey, fish, shellfish and all other animal-based proteins are high-quality, or complete proteins. They contain each of the indispensable amino acids, including methionine and lysine, which you need to get from your diet because your body cannot produce them, according to the Institute of Medicine. Lean meat with the visible fat removed, skinless, white-meat poultry, fish and shellfish are high in protein and essential minerals, and low in saturated fat.
Eggs and Dairy
The protein from eggs and dairy products, such as cottage cheese, milk, yogurt and cheese, is complete, so it provides both methionine and lysine. Milk, yogurt and cheese are also good sources of calcium, which is necessary for building and maintaining strong bones, and fortified products supply vitamin D, which helps your body absorb calcium from your food. Whole eggs, whole milk and full-fat yogurt and cheese are higher in calories and saturated fat than egg whites and low-fat or fat-free dairy products.
Soy-Based Proteins
Soy protein is an example of a complete protein from a plant-based source, so it is suitable for strict vegetarians, or vegans, who avoid all animal-derived products. Tofu roasted soybeans, edamame, or green soybeans, tempeh, soymilk and soy yogurt are all sources of methionine and lysine. Soy products may be high in calcium, iron, zinc and fiber, and they are naturally cholesterol-free and low in saturated fat, according to the University of Michigan.
Protein Combining
Many plant-based proteins are incomplete, which means that they are lacking one or more of the essential amino acid, such as methionine or lysine, according to the University of Michigan. Grains, such as bread, pasta and cereals, vegetables and legumes, including beans, peas and lentils, are incomplete proteins. Protein combining is the principle of eating multiple sources of incomplete proteins to make a complete protein. The University of Michigan suggests a peanut butter sandwich, a pita with falafel or a bean burrito with a corn tortilla to get complete proteins.
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