July 28, 2016
This post is the first in a series, Protein—Everything You Always Wanted to Know But Were Too Afraid to Ask. Check out the second post on pulses!
Not necessarily. First, let’s first break down what, exactly, protein is and why it’s important for our health.
Protein is an important energy-yielding macronutrient – meaning it provides us calories, or energy. Proteins build muscle and make up hemoglobin, which transports oxygen to our muscles. Proteins also have functional and structural roles building and repairing tissues. They are key players in signaling and chemical reactions as well–including enzymes and hormones.
Through a microscope, proteins look a bit like necklaces with beads that come in different shapes and sizes. To further the analogy, think of each bead as a different type of amino acid: each protein in our body has a specific amino acid sequence, and proteins typically contain from 50 to 2,000 amino acids connected in various combinations.[i] . (That’s a lot of beaded necklaces!) What makes this interesting is that there are only 20 standard amino acids—but proteins, and their functions, exist in a multitude of varieties because of which amino acids are present and in what order they are put together.
Animal or vegetable?
Meat is a good source of protein, but it is not the only option. Plants have plenty of protein, too, especially beans, legumes, nuts and some grains. The primary difference between plant and animal proteins is the amino acid profile.
There are some amino acids that we only obtain from the food we eat; they are not produced by our body. These are called essential amino acids. Proteins from animals have a complete package of these essential amino acids, while plant proteins may be missing one or two. This shortage can slow down the efficiency in which the amino acids are used to build proteins. However, because we eat different types of plant proteins, what one is missing, another provides. So, for example, eating rice with a legume provides a full set of amino acids. Problem solved.
There are other differences in what we can call the “protein package,” that is, the foods that contain the protein.
- Animal proteins contain heme iron, which is more available for use. Plant sources have non-heme iron, which is less available for use. However, eating foods that contain vitamin C or other heme-containing foods along with the non-heme protein enhances the iron bioavailability.
- Plant protein foods contain fiber, while animal proteins do not. Dietary fiber improves digestion and promotes satiety. It has also been associated with lower blood sugars and body weight.
- Protein foods differ in the amount and type of fat they contain. Many animal proteins are higher in fat, particularly saturated fat, which is associated with heart disease and other chronic diseases. Seafood contains heart-healthy omega-3 fatty acids. Most plant proteins are very low in fat or contain healthier oils such as those in almonds and other nuts.
- Red meat and processed meat have strong links to risk of heart disease, stroke, cancer and diabetes. Substituting nuts, low-fat dairy or whole grains for meat appears to lower the risk of developing diabetes.
- Both animal and plant sources of protein have a variety of important minerals and vitamins. B-12 is the only vitamin available solely in animal foods. If an individual occasionally eats meat, eggs or dairy, they will obtain sufficient B-12. A strict vegan may need a B-12 supplement.
- Creatine is a nonessential amino acid made by the liver, kidneys, and pancreas, but is also present in animal protein. Creatine is stored in the muscle and used for energy. It tends to be lower in the muscles of vegetarians. Creatine supplementation may be beneficial for performance athletes and people with health conditions, but more research is being done in this area.[iii]
How much do we really need?
Protein needs vary from person to person depending on their health, activity and body composition. Protein needs are higher during growth, pregnancy or healing, during an exercise or weight lifting program, and when overall calories are depleted (to prevent muscle break down).
The Institute of Medicine recommends that adults consume a minimum of 8 grams of protein for every 20 pounds of body weight daily.[iv] However, it also sets a wide range for acceptable protein intake—anywhere from 10 to 35 percent of calories each day. As an example, a 150 lb. person’s protein needs could vary from 55-90 grams.
To look at meeting the minimum protein needs for health, the Recommended Daily Allowance is 46 grams per day for women over 19 years of age and 56 grams per day for men over 19 years of age.[v] This is equivalent to 1.6 ounces of meat for women and 2 ounces for men. A serving the size of a deck of cards is 3 ounces. Essentially, half a piece of chicken will meet the daily protein requirement for the average adult woman.
There is relatively little information on the ideal amount of protein in the diet or the healthiest target for calories contributed by protein, mostly due to substantial individual variation. There is some evidence that eating a high-protein diet in place of a high-carbohydrate diet (mostly refined flours and sugars) may be beneficial if the protein is from healthy plant sources, but not from high-fat animal sources such as red meats, processed meats and high-fat dairy.
Timing actually matters.
Although most Americans meet or exceed their protein needs, there may be some additional benefits of spreading out their daily protein intake. Typically, Americans eat most of their protein in the second half of the day–toward lunch and dinner. However, eating moderate protein throughout the day–starting at breakfast—increases the efficiency at which protein is utilized to build muscle. This is especially beneficial for athletes and those trying to lose weight. To maximize the rebuilding of muscles and protein use, aim for 20-30 grams of protein at each meal, which is the maximum that muscles can synthesize at one time.
Can I get enough protein from plant-based foods?
A one-ounce equivalent from the protein foods group is equivalent to 1 ounce of meat, poultry or fish, 1/4 cup beans (cooked), 1 egg, 1 tablespoon of peanut butter, or ½ ounce of nuts/seeds. With a proper combination of sources, vegetable proteins provide adequate protein and nutrients as well as many additional health benefits.
Below are examples of animal and plant-based foods and the protein they contain: [vi]
|Food item||Typical serving||Protein (grams)|
|Hamburger patty||3 ounces||20|
|Chicken breast||3 ounces||28|
|Fish, salmon||3 ounces||22|
|Pinto beans, cooked||½ cup||11|
|Green peas, cooked||½ cup||5|
|Chick peas, canned||½ cup||7.5|
|Lentils, cooked||½ cup||9|
|Peanut butter||2 Tablespoons||7|
|Tofu||4 ounces, ½ cup||11|
|Quinoa, cooked||1 cup||8|
|Brown rice, cooked||1 cup||5|
|Oatmeal, cooked||½ cup||3|
|Seitan (wheat gluten)||3 ounces||21|
|Milk, 2%||1 cup||8|
|Greek yogurt, low fat||7 ounces||20|
|Cheddar cheese||1 ounce||6.5|
Photo Courtesy: National Human Genome Research Institute[ii]
[i] US Department of Agriculture, National Institute of General Medicines, The Structures of Life: Chapter 1: Proteins are the Body’s Worker Molecules; NIH Publication No. 07-2778; Reprinted July 2007 https://publications.nigms.nih.gov/structlife/chapter1.html
[iii] Casey A., Greenhaff P., Am J Clin Nutr, August 2000, vol. 72 no. 2 607s-617s
[iv] Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). 2005, National Academies Press
[v] Based on reference weights of 57 kg. (125 lb.) for women and 70 kg. (155 lb.) for men.
[vi] US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Release 28. Version Current: September 2015. Internet: http://www.ars.usda.gov/nea/bhnrc/ndl