What is Protein?
26 May 2021
Global protein consumption has risen over 45% since 2000, as the growing middle class increasingly seek health benefits from the food they eat1. Yet, many consumers struggle to understand protein2, exhibiting a low knowledge of what proteins are, how much they need, which sources have high protein levels, or even if these sources are considered to be of good nutritional quality.
In this article, we break down the basics of what you need to know about proteins, uncover high-quality protein sources and explore two of the most common protein types, casein and whey.
Proteins Are Made of Amino Acids
Our bodies use amino acids as building blocks of proteins, which bind together to create peptide chains arranged and folded into specific structures. Proteins play a structural and functional role in every cell in our bodies, such as skin, organs, muscles and bones.
Of the 20 amino acids, 11 can be made by the body, classified as non-essential, and do not have to be supplied via our diets. The other nine amino acids are essential because they cannot be made by the body, so must be supplied via our diets. If a food source contains all nine, it is known as a high-quality, complete protein.
Essential amino acids must be consumed each day to replace the amino acids lost during normal metabolism and to rebuild and repair the body. Protein provides amino acid, such as leucine, for the muscle to build new proteins, known as muscle protein synthesis (MPS)3.
Diagram taken from "What are proteins made of?" infographic
There Are High Levels of Protein in Dairy Milk
Food proteins vary depending on their amino acid content and contain varying levels of essential and non-essential amino acids. Dairy is an ideal protein as:
- It contains one of the highest levels of the nine essential amino acids4
- It is highly digestible, meaning per gram of protein more essential amino acids from dairy are available to the body than other protein sources
- Protein absorption is quick and stimulates lean muscle growth to a greater extent than other protein sources
There are a vast range of tasty and nutritious products, many of which are good sources of protein. An example would be milk, which is the most commonly known dairy product and is a high quality source of protein. There are two types of protein in milk, composed of 80% casein protein and 20% whey protein.
Diagram taken from "What is milk composed of?" infographic
Understanding the Breakdown of Casein vs Whey
The main difference between casein and whey protein is the speed of digestion. Casein protein digests slowly and can be used to provide a steady stream of amino acids throughout the day, or throughout the night when taken before sleep. In comparison, whey protein is often consumed post-exercise as it can be quickly absorbed due to its amino acid profile of being high in branched-chained amino acids (BCAAs) like leucine.
However, this does not mean that one type of protein is better than the other. Understanding the differences between the proteins found in milk can help you determine which better suits your health and fitness goals.
Diagram taken from "Casein vs Whey" infographic
Dairy Protein for All Goals
Eating enough protein daily, by easily incorporating dairy protein into a balanced diet throughout the day to provide excellent levels of all essential amino acids, and also leads to feelings of fullness, which may assist with managing weight.
Explore the benefits of protein and how you can optimize them for your health and nutrition goals.
-  The Future of Protein Demand in Asia, Food Industry Asia
-  Nielsen. (2018). Protein: Consumers Want It, But Don’t Understand It. Retrieved from https://www.nielsen.com/us/en/insights/news/2018/protein-consumers-want-it-but-dont-understand-it.html
-  Bennet W M, Connacher A A, Scrimgeour C M, Smith K & Rennie M J (1989). Increase in anterior tibialis muscle protein synthesis in healthy man during mixed amino acid infusion: studies of incorporation of [1-13C] leucine. Clinical Science (London, England: 1979), 76, 447–454.
-  Rutherfurd S M, Fanning A C, Miller B J & Moughan P J (2015). Protein digestibility-corrected amino Acid scores and digestible indispensable amino Acid scores differentially describe protein quality in growing male rats. The Journal of Nutrition, 145, 372–379.