Protein is a macronutrient necessary for the proper growth and function of the human body. There is considerable debate over the amount of protein a person needs to consume per day, the current recommended daily intake (RDI) for protein is 46 grams for women aged 19-70, and 56 grams for men aged 19-70. Any excess protein is turned into energy by the body, and it is controversial whether this excess protein causes a strain on the liver.
A deficiency in protein intake leads to muscle atrophy, inability to build muscle,and impaired functioning of the human body in general.
High protein foods include meat, fish, cheese, tofu, beans, lentils, yogurt, eggs, nuts, and seeds. Below is a list of foods with the highest protein to calorie ratio, for more information, see the sections on protein dense foods, other protein rich foods, low calorie high protein snacks, and protein isolates.

1. Fish (Cod, Tuna, Salmon) Other fish high in protein per fillet(3oz or 85g): Tuna (22g), Salmon (22g), Halibut (22g), Snapper (22g), Perch(21g), Flounder and Sole (21g), Cod (20g), Tilapia (17g).
2. Cheese (Non-fat Mozzarella) Other cheese high in protein per ounce(28g): Low-fat Cottage Cheese (5g), Low-fat Swiss Cheese (8g), Low-fat Cheddar (6g), Parmesan (10g), Romano (9g). *Low or Non Fat Mozzarella and Cottage Cheese provide the most protein per calorie, full fat cheeses typically only provide 1g protein per 20 calories, and are less optimal sources of protein.
3. Lean Turkey and Chicken (Turkey Breast) More Chicken and Turkey: Chicken Leg – Drumsticks (60g) provides 16g protein. Chicken Thigh (37g) provides 9g protein. 3oz serving of Chicken Breast (85grams) provides 14g protein.
4. Lean Beef and Veal (Low Fat) T-Bone Steak 3oz (28g) provides 19g of protein, 1 Piece of Beef Jerky (20g) provides 7g of protein.
5. Pork Loin (Chops) Sirloin Roast 3oz (28g) provides 23g of protein, Ham 3oz (28g) provides 18g of protein, 1 slice of bacon (8g) provides 3g of protein.
6. Tofu cup (252g) of firm tofu provides 20g protein. 1 cup of soft tofu (248g) provides 16g protein. 1 cup of tempeh (166g) provides 31g protein.
7. Beans (Mature Soy Beans) Other beans high in protein per cup cooked: Kidney Beans (17g), White Beans (17g), Lima Beans (15g), Fava Beans (14g), Black Beans (15g), Mung Beans (14g)
8. Yogurt, Milk, and Soymilk 1 cup skim milk (245g) provides 8g protein, 1 cup soymilk (243g) provides 8g protein.
9. Eggs (Especially Egg Whites) 1 Egg White (33g) provides 4g protein, 1g protein to 4.4 calories. 1 cup of scrambled eggs (220g) provides 22g protein.
10. Nuts and Seeds (Pumpkin, Squash, and Watermelon Seeds) Other nuts and seeds high in protein (grams protein per ounce (28g)):Peanuts (7g), Almonds (6g), Pistachios (6g), Sunflower Seeds (6g), Flaxseed (5g), Mixed Nuts (4g)”