Protein is part of every tissue, including your organs, muscles and skin, and plays a major role in your body — from building, repairing and maintaining tissues, to making important hormones and enzymes, to transporting nutrients. Since an adequate protein intake is important throughout our lives, especially as we age, it's smart to know about the different types of protein, how much you need to consume and what foods provide a good source of this powerful nutrient.
The Building Blocks of Protein
Amino acids are organic compounds that combine together in long chains to make proteins. Considered the building blocks of protein, there are 20 different amino acids needed by the body. Some amino acids are considered essential because the body doesn't make them and you need to get them from food. Other amino acids are made by the body, so they're considered nonessential.
Types of Protein
There are two types of protein: complete and incomplete. Complete proteins have the right proportions of all the essential amino acids. They come from animal sources like eggs, milk, meat, poultry and fish, as well as foods made from soy, such as tofu and tempeh. Incomplete proteins are low in one or more essential amino acids. This includes most plant proteins, such as beans, rice and nuts. You can combine some incomplete proteins, including beans and rice, to get a protein that is considered complete.
How Much Do You Need?
The amount of protein you need each day varies based on your age, gender and activity level. For healthy adults, the Food and Nutrition Board of the Institute of Medicine recommends getting a minimum of 0.8 grams of protein for every kilogram of body weight each day1. This is equal to about seven grams of protein for every 20 pounds of body weight, which would be 56 grams of protein per day for someone who weighs 160 pounds.
However, current research and expert opinion show that 0.8 grams of protein per kilogram of body weight per day may not be enough as we age. The current recommendations were made based on research in young adults and do not promote optimal health or protect older adults from sarcopenic muscle loss (loss of muscle and function with aging). Experts now estimate that older adults need 1.0 to 1.2 grams of protein per kilogram of body weight or higher per day. Additionally, researchers recommend that adequate protein intake with each meal is important to promote protein anabolism (or protein building). These recommendations state that an intake of 25 to 30 grams of high-quality protein per meal is necessary for optimal muscle protein synthesis, which is particularly beneficial for older adults trying to maintain muscle mass2.
Good Sources of Protein3
- Tuna (6 ounces, packed in water): 40 grams
- Fish (6 ounces, cod or salmon): 40 grams
- Chicken (4 ounces, skinless): 35 grams
- Lean red meat (4 ounces): 35 grams
- Lean pork (4 ounces): 35 grams
- Tempeh (1 cup): 31 grams
- Tofu (1/2 cup, raw, firm, prepared with calcium sulfate): 20 grams
- Cottage cheese (1 cup, 1% or 2% fat): 28 grams
- Black beans (1 cup, mature seeds, canned, low sodium): 14 grams
- Edamame (1 cup, frozen, prepared): 17 grams
- Yogurt (1 container, 170 grams, Greek, plain, nonfat): 17 grams
- Milk (1 cup of 1%, 2% or fat-free): 8 grams
- Almonds (1 ounce): 6 grams
1. Institutes of Medicine of the National Academies, Dietary Reference Intake for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acid. September 5, 2002.
2.Gaffney-Stomberg E, Insogna KL, Rodriguez NR, Kerstetter JE. Increasing Dietary Protein Requirements in Elderly People for Optimal Muscle and Bone Health. J Am Geriatr Soc. 2009 Jun;57(6):1073-9
3. United States Department of Agriculture. National Nutrient Database for Standard Reference. December 7, 2011. http://ndb.nal.usda.gov