A friend of mine recently asked me about protein. She was unsure of what she should be consuming, so I decided to share with you what I shared with her.
Protein is an important part of our diet because proteins form basic structural material within our muscles, bones, tissues, skin, and organs. They also provide support functions that help our daily processes, and are a vital to our health and healing.
Proteins are made up of amino acids, each with a distinct property, which assemble together to make larger molecules. They can assemble in different ways to provide various forms and functions within the body.
I will first tell you more about amino acids, and then explain how that translates into the protein needs for our daily eating habits. I will also share a bit about protein supplementation, and why they may not be as effective in exercise or sports performance as we would want them to be.
What are Amino Acids?
Amino acids are the structural units of protein. There are 20 amino acids needed to build proteins in the body. Nine are indispensable or essential, five are dispensable or non-essential, and six are conditionally indispensable or conditionally essential.
The Nine Indispensable Amino Acids.
Nine amino acids cannot be made in the body, and must be supplied through the food we consume. These are called indispensable amino acids, and are also known as essential amino acids because they need to be an essential component of our diet. The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. There is no need to remember these, and below I’ll provide examples of how to make sure we are getting essential amino acids in our diet (Marieb & Hoehn, 2013).
The Five Dispensable Amino Acids.
Five amino acids can be made in adequate amounts in the body. These are known as dispensable amino acids or nonessential amino acids, and include alanine, aspartic acid, asparagine, glutamic acid, and serine. These amino acids are typically made in the liver, but can also be made in other parts (Marieb & Hoehn, 2013).
The Six Remaining Amino Acids.
Finally, the body makes the remaining six amino acids, but it is not able to make them in enough quantity when there is another high demand or need, such as when we are ill or under a lot of stress. They are called conditionally indispensable amino acids because we need to consume them in our diets only during certain periods of time. They are arginine, cysteine, glutamine, glycine, proline, and tyrosine. For example, the liver makes arginine. But in a newborn, the liver cannot yet make enough arginine to supply the body’s needs, and thus it needs to be supplied through breast milk or formula (Marieb & Hoehn, 2013).
What do Proteins Do In the Body?
Proteins are present in muscle cells and help aid in the structure and function of muscles. In addition, proteins are essential to the immune system. For example, antibodies and complement proteins both support immune responses. Antibodies help fight foreign substances, and complement proteins boost the overall response of the immune system. Also, other types of proteins help in creating new proteins, causing chemical reactions in the body, transporting elements throughout the body and in maintaining the body in a healthy state (Marieb & Hoehn, 2013).
What Does This Mean For Our Diet?
The body does not store protein, as it does glucose and fat. As a result, we have to consume protein to make sure we have enough for our bodily functions.
Animal and plant foods offer a good source of protein, but all amino acids are not equally available on all animal and plant foods. Food proteins have an amino acid score, which is based on the types of amino acids the food provides and how easily the body can digest them. The Food and Agriculture Organization is proposing to call this score the Digestible Indispensible Amino Acid Score.
Regardless of the terminology, the higher score, the more “complete” the protein. For example, eggs have a score of 100 in both amino acid composition and digestibility, and are thus one of the most complete forms of protein available (Schlenker & Roth, 2011). Other examples of animal foods are milk, cheese, beef, pork, other meats, poultry, seafood, and fish.
Animal proteins have higher amino acid composition, and are thus considered complete proteins, whereas plant proteins vary in their content and quality of amino acids, and are considered incomplete proteins (Schlenker & Roth, 2011).
In order to make up for the variability in amino acid content, plant proteins are complemented with other plant proteins or other foods, and when eaten together, they provide the same essential amino acids that a complete animal protein would (Mahan, Escott-Stump, & Raymond, 2012). Examples of plant proteins are legumes, nuts, rice, and seeds. Possible food combinations that provide complete proteins include grains and legumes (for example, rice and lentils, rice and beans, or tortillas and beans), grains and dairy (such as pasta and cheese, bread and cheese, oats and milk, or cereals and yoghurt), and legumes and seeds (like garbanzo beans and sesame seeds, which is found in hummus).
These combinations are particularly important for those who are vegan or vegetarian and consume little to no animal protein. But, they can be consumed by all of us, regardless of our dietary preferences or needs. Consuming the right proteins is key to be able to obtain all of the essential amino acids our bodies require.
What About Protein Supplements?
There are a myriad of protein supplements available in the market. Some of us consume protein supplements as an additional supplementation to our diet. If so, it is important to consider supplementing with amino acids we are not getting through our food. Others take protein supplements to enhance exercise performance.
Studies have shown that protein supplements do not always result in improved exercise performance. For example, creatine is an amino acid used to produce muscle as well as to produce energy used by the muscle (Mahan et al., 2012). Creatine is often taken as a sports supplement to boost the body’s performance. I found two studies that showed creatine supplementation did not have a significant impact on exercise.
The first study looked at creatine supplementation versus glutamine supplementation. Glutamine is another amino acid found in muscle tissue. The study was conducted on 32 male military police officers, where 10 received creatine, 10 received glutamine, and 12 received a placebo. All the men went through 90-minute training sessions five times per week. Yet, at the end of the study there were no statistically significant differences in muscle strength and performance amongst the groups (da Silveira et al., 2014).
The second study tested the effects of a creatine supplement and an alanine supplement on 32 female participants. Alanine is another amino acid, and beta-alanine is believed to increase muscle performance. Eight participants received beta-alanine, another eight received creatine, nine received a combination of beta-alanine and creatine, and seven received a placebo. The participants engaged in moderate exercise for 30 minutes per day, three days a week, for three months. There were no significant improvements in exercise performance amongst the women (Kresta et al., 2014).
Protein supplements are considered safe if consumed in moderation. But, keep in mind they do not have a marked effect on long-term exercise or on physical performance, and thus should only aid in adding essential or conditionally essential amino acids to our diet. However, the best course of action is to ensure proper protein consumption through the foods we consume.
da Silveira, C. L., de Souza, T. S. P., Batista, G. R., de Araujo, A. T., da Silva, J. C. G., de Sousa M. doS., C., Marta, C., & Garrido, N. D. (2014). Is long term creatine and glutamine supplementation effective in enhancing physical performance of military police officers? Journal of Human Kinetics, 43, 131-138. doi://10.2478/hukin-2014-0098
Kresta, J. Y., Oliver, J. M., Jagim, A. R., Fluckey, J., Riechman, S., Kelly, K., Meininger, C., Mertens-Talcott, S.U., Rasmussen, C., & Krider, R. B. (2014). Effect of 28 days of beta-alanine and creatine supplementation on muscle carnosine, body composition, and exercise performance in recreationally active females. Journal of the International Society of Sports Nutrition, 11(1), 55-59. doi:10.1186/s12970-014-0055-6
Marieb, E.T., & Hoehn, K. (2013). Human Anatomy & Physiology (9th ed.). Glenview, IL: Pearson Education.
Mahan, L. K., Escott-Stump, S., & Raymond, J. L. (2012). Krause’s Food and The Nutrition Care Process (13th ed.). St. Louis, MO: Elsevier Saunders.
Schlenker, E. D. & Roth, S. L. (2011). Williams’ Essentials of Nutrition and Diet Therapy- Revised Reprint (10th ed.). St. Louis, MO: Elsevier Mosby.