There are 3 general classifications for food: protein, fat, and carbohydrate. This article is about protein. We'll talk about what it is, why you need it, how to get it, and how much you need in order to be healthy.
Why We Need ProteinBefore we get into the details of what protein is, let's get motivated by appreciating what protein does. Our bodies use protein to build just about everything. Skin, hair, muscles, organs, even the hemoglobin in your blood is made of protein. And the list goes on: The enzymes that break down food and spark chemical reactions in the body are proteins. Our immune systems depend on protein to make antibodies. Protein molecules aid the transfer of messages between the neurotransmitters in our brains. And many hormones, including insulin and other metabolism regulating hormones, are proteins as well.
I bet you're thinking where's the protein? Let me at it. But before we go there, we should sneak in a little bit of science about what protein actually is. Protein molecules are made of smaller molecules called amino acids. There are twenty naturally occurring amino acids. Some names you might be familiar with are lysine, glutamine, and tryptophan. When you eat foods that contain protein, your body breaks those proteins down and reassembles the the amino acids to create the protein structures it wants to make.
The human body can synthesize eleven of the amino acids it needs. However, nine amino acids are called essential amino acids because they must be taken in from food. When a single food provides all nine (yes, it used to be eight) essential amino acids it is called a complete protein. Many foods contain high levels of some amino acids and not others. In that case, foods have to be combined in order to provide all nine amino acids. When foods go together to create a complete protein profile they are called complimentary proteins.
Sources of ProteinMost people think of meat when they think of protein. And that's correct. Meat from land animals, fish, and fowl are all high protein foods. However, nuts, seeds, beans, and dairy products are high protein foods as well. And whole grains such as brown rice, whole wheat, quinoa, barley and amaranth; and some vegetables, like avocados and sprouts, can be significant sources of protein too. Meat, dairy and eggs are complete proteins. To get a complete protein, most grains, nuts, seeds, and vegetables have to be combined. Rice and beans or corn and beans are famous examples of complimentary proteins. It is worth noting that you don't have to get all essential amino acids in one meal. Amino acids are not stored by the body but they do stay available long enough to be used and combined throughout a day. With so many sources of protein, eating a healthy, varied diet generally provides enough amino acids for the average person -- even if they exercise.
How Much Protein You NeedPeople do have different protein requirements depending on their age, their size, their levels of activity and health. However, those requirements are not as high, and don't vary as much, as some of the popular hype around protein might lead one to believe. The U.S.D.A recommends 5.5 ounces of protein for women 19-30 years old. For all other women's age groups they recommend 5 ounces. For men, 6.5 ounces for 19-30 years old, 6 ounces for 31-50 years old, and 5.5 ounces for over 51. 5 ounces is about 142 grams. 6 ounces equals about 170 grams.
Some nutritionists, and the World Health Organization (W.H.O), believe the U.S.D.A standards are too high. The W.H.O recommends 8 grams of protein for every 20 lbs. for adults. By those standards, an adult woman weighing 130 lbs. would only need 52 grams of protein - less than half of what the U.S.D.A. suggests. An adult male of 180 lbs. would need 72 grams. Again, less than half. The discrepancies between the U.S.D.A and the W.H.O may reflect special interest pressures on those groups. At any rate, one might surmise that the U.S.D.A numbers are at the top end of any reasonable scale.
As a reference, the U.S.D.A offers the following guidelines as to what serving sizes equal an ounce of protein: "In general, 1 ounce of meat, poultry or fish, ¼ cup cooked beans, 1 egg, 1 tablespoon of peanut butter, or ½ ounce of nuts or seeds can be considered as 1 ounce equivalent from the Protein Foods Group."
See a chart showing ounce equivalents in typical serving sizes
Protein and ExerciseWith protein being the stuff of muscles, one might assume that those who exercise need a lot more protein, but this is not the case. First, it is important to know that protein is not the body's preferred fuel for a workout -- carbohydrate is. Protein is important after a workout to repair and build muscle. But it doesn't take much more protein to do that -- an ounce or two for most people who exercise at moderate intensity. For those engaged in intensive strength training or for endurance athletes, the recommendation is at most twice the amount of protein the average person needs.
Read about Protein for Body Building
Protein SupplementsAnother way to get protein in your diet is through supplements. Amino Acids can be found in pill form, individually and in complete protein combinations. More popular, however, are powdered proteins sourced from any variety of foods. Powdered whey (from milk) protein is very popular, as is soy protein. There are also protein powders made from rice, sprouts, even hemp. Many people find supplemental protein easy to digest and enjoy protein powders blended in health shakes as a way to get nutrition without bulk in the belly.
Protein Shake Recipes
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Haas, E. (1992) Staying healthy with nutrition. Berkley: Celestial Arts
Holford, P. (2004) The new optimum nutrition bible. Berkley/Toronto: Crossing Press
Nutrition for Everyone: Protein, CDC.gov
U.S.D.A, Dietary Guidelines for Americans 2011