Protein, an essential nutrient in the human diet, can be found in animal-based and plant-based foods. It's one of the three macronutrients every person needs, alongside carbohydrates and fats. The two basic types of protein found in food are complete and incomplete proteins. Eat a wide variety of both types to ensure that your body is getting the nutrition it needs.
Amino Acids
Amino acids are the building blocks of dietary protein. When you consume protein in food, it gets converted to amino acids in your body and is then utilized in different ways, such as to build new muscle. There are 20 different amino acids that combine to form proteins. Nine of these amino acids are called essential amino acids, because they cannot be produced by the human body and so must be taken in through food.
Complete Proteins
Food sources that contain all nine of the essential amino acids are known as complete protein sources. These are also sometimes referred to as high-quality proteins. Complete proteins are found primarily in animal-based foods, such as beef, fish, pork, chicken, turkey, eggs, cheese and milk. A cup of milk has a total of about 8 g of protein; a 3-oz. portion of meat can contain about 21 g of high-quality protein.
Incomplete Proteins
Incomplete proteins do not contain all nine of the essential amino acids. However, this doesn't mean you shouldn't consume incomplete protein food sources. Incomplete proteins are found in plant-based foods like corn, rice and beans. You can combine certain incomplete proteins to form a complete protein source, such as eating rice and beans together.
RDA
Most Americans already get enough protein in their current diet, according to the Centers for Disease Control (CDC), so there's no need to supplement it in most cases. The recommended dietary allowance (RDA) for young children to teens is 13 g to 52 g, depending upon age and gender; males require slightly more protein than females. The RDA for adult women and men is 46 g and 56 g per day, respectively. The CDC does not specify how much of the RDA should come from complete or incomplete protein sources, saying a well-balanced diet consisting of a wide variety of healthy foods will help you achieve the optimal amount of both. Healthy foods include vegetables, fruits, whole grains, lean cuts of meat, low-fat dairy and nuts, seeds and legumes.
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