Protein is a building block for muscles, plays a role in the immune system and is needed for the function of all cells and organs. The body uses protein to create hormones and digestive enzymes and to repair damage to cells and tissues; it is certainly essential to health. Studies show that most adults in the United States get more than enough protein in their diets, but many people still have questions about this important nutrient. How much protein does a person need and is it necessary to get it from meat or animal products? Many people still believe it is necessary to combine certain foods to create an optimal or complete protein profile, but current research shows otherwise.
Which Foods Contain Protein?
Animal foods such as meat, poultry, fish, eggs and dairy contain protein. There is also protein in soy foods, legumes like beans and peas, nuts, seeds, whole grains, and some vegetables and fruits. All proteins are made of amino acids, or the building blocks of complete proteins. Nine of the 20 total amino acids are considered "essential" meaning they must be consumed in the diet rather than manufactured by the body. Animal foods contain all 20 amino acids together. Plant foods also contain all 20 amino acids, but are lower in some of the essential amino acids. For example, rice contains lysine but not in high quantities. Beans contain methionine, but again, at low levels.
Is There a Need to Combine Plant-Proteins?
In the past, it was believed that people who do not consume animal proteins must combine plant proteins to make up for the missing essential amino acids. For example, since rice is low in the amino acid lysine, but beans are a rich source of lysine yet low in methionine, then a person should eat these foods together to get access to all 20 amino acids. This idea was very popular in the 1970's but questions remain about the importance of protein combining or "complimentary proteins". Research now tells us that the body is capable of obtaining the amino acids it needs for health as long as a variety of foods that contain all amino acids are consumed in the diet. A varied diet creates a pool of amino acids the body can use. There is no need to consume all 20 amino acids at each meal, and this idea is now considered irrelevant if you follow a healthful diet.
Protein for Optimal Health
Current recommendations regarding the dietary allowance for protein states that adult women require about 46 grams of protein per day and men require 56, or that protein should make up 10-30 percent of total calories consumed. Of course, there are circumstances that change those requirements, such as body weight, athletic needs, pregnancy, certain medical conditions and age. To better assess your unique needs, meet with a medical professional or dietitian who can calculate protein requirements based on your history and goals. However many grams you are aiming for, rest assured that you can achieve your protein needs with a vegetarian or vegan diet and there is no need to combine certain foods to meet these needs. Eating a varied diet of whole grains, fresh produce, and legumes can meet all of your protein needs.
Ginger Hultin, MS, RD, LDN is a Chicago-based dietitian who specializes in integrative oncology. With a Master's degree from naturopathic Bastyr University, she practices plant-based nutrition and specializes in lab interpretation and appropriate supplementation. Ginger also had a passion for fitness and maintains both group fitness and personal training certifications.