Most people over the age of 18 need 10 to 35 percent of their daily calories from protein. When you consume protein, your body breaks it down into amino acids. There are nine essential amino acids that your body cannot synthesize. It is important to obtain all nine essential amino acids from your diet throughout the day.

The best sources of protein contain all nine essential amino acids. These are called high biological value, or complete, proteins, and they also provide other important nutrients. Listed below are the seven best sources of protein.

1. Lean Poultry

Chicken, turkey, Cornish hen, and wild duck or goose are lean poultry sources. Poultry is considered lean if both the skin and fat are removed, and it is cooked using a dry heat method, such as grilling or baking. One ounce of lean poultry provides 7 grams of protein, as well as iron, magnesium, zinc and other important minerals.

2. Fish

Salmon, tilapia, halibut, tuna and mackerel provide 7 grams of protein per ounce, all the essential amino acids, as well as essential unsaturated fatty acids, including EPA and DHA. Some fish varieties, including salmon, are among the few dietary sources of vitamin D.

3. Quinoa

Quinoa is a seed that resembles a grain. It is a good vegetarian source of complete protein and also a good source of fiber. Try substituting quinoa in place of rice or pasta.

4. Eggs & Egg Whites

One egg, two to three egg whites or one-quarter cup egg substitute each contain around 7 grams of protein and all the essential amino acids. The yolk of the egg contains important vitamins and minerals, such as vitamin A, vitamin B12, riboflavin and folate. It is among the few dietary sources of vitamin D. The yolk also contains cholesterol. The Harvard School of Public Health recommends limiting your yolk consumption to no more than three per week if you have diabetes or heart disease.

5. Dairy

Dairy products contain all nine essential amino acids, as well eight grams of protein per serving. Dairy and fortified dairy are good sources of many vitamins and minerals, including vitamin D, calcium and potassium. Low-fat and non-fat dairy products may be a better option for you if you're trying to limit your saturated fat and cholesterol intake.

6. Lean Meat

Lean meat may include beef, pork or veal. It contains all the essential amino acids, 7 grams of protein per ounce, and, like poultry, is a good source of iron and zinc. As with poultry, lean cuts of meat should be trimmed of fat and cooked using a dry heat method, such as grilling.

7. Soy

Soy is another good vegetarian source of protein. There are many soy products that contain all nine essential amino acids, as well as many of the same nutrients as lean poultry or meat. You can also find soy products that taste similar to animal protein products.