Essential Nutrients: Protein

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One of the most crucial components of a healthy lifestyle.

Protein is one of the most important parts of the human body. It is a macronutrient, and it is essential for growth and repair of the body and maintenance of good health.[3] It is also required for building and repairing muscle and plays an important role in how the body responds to exercise, which is why products containing protein are extremely popular for professional and amateur athletes alike.[2] Proteins are made up of amino acids, and different foods contain different amounts and different combinations of amino acids.[3] Protein from animal sources (e.g. meat, fish, eggs and dairy products) contains the full range of essential amino acids needed by the body, and combinations of plant based proteins deliver the full range as well.[3] For adults, the average requirement of 0.6g of protein per kilogram body weight per day is estimated, but there is an extra requirement for growth in infants and children and for pregnant and breastfeeding women.[3]

What is it and what does it do?

As previously mentioned, proteins are made up of different combinations of amino acids. These are the building blocks of protein, and ensure that all the proteins fulfil their prospective duties. There are about 20 different amino acids commonly found in plant and animal proteins. For adults, 8 of these, have to be provided in the diet and are therefore defined as ‘essential’ or ‘indispensable’ amino acids. These are: Leucine, Isoleucine, Valine, Threonine, Methionine, Phenylalanine, Tryptophan, Lysine.[3] The functions of proteins are extremely varied, and include catalysing metabolic reactions, DNA replication, providing structure to cells, and transporting molecules from one location to another.[6] However, the best-known role of proteins in the cell is as enzymes, which catalyse chemical reactions. Enzymes are usually highly specific and accelerate only one or a few chemical reactions. Enzymes carry out most of the reactions involved in metabolism, as well as manipulating DNA.[6] The scientific history of protein is surprisingly old, as proteins were first recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy.[6] Noted examples at the time included albumin from egg whites, blood serum albumin, fibrin, and wheat gluten.[6] After proteins were first described and named (in the 19th Century by Dutch chemist Gerardus Johannes Mulder by Swedish chemist Jöns Jacob Berzelius respectively), insulin was the first to have its amino acid sequence identified, and this was by Frederick Sanger in 1949.[6]

Health Benefits

As well as being essential for the function of the human body, protein provides other nutrients. For example, for those that eat meat, oily fish such as sardines, mackerel or salmon, contain omega-3 fatty acids, which are heart healthy. Oily fish are also good sources of vitamins A and D.[5] It is also often used in combination with exercise for muscle gain, as studies show that the addition of 15-25g of protein to a post-workout meal or snack can boost glycogen storage, reduce muscle soreness and promote muscle repair.[1] However, it is a common misconception that high protein intakes alone increase muscle mass, and focusing too much on eating lots of protein can mean not getting enough carbohydrate, which is a more efficient source of energy for exercise.[4] One of the great things about protein is that there are many good sources of it. Lean meat, poultry, fish, eggs, milk and milk products such as cottage cheese and Greek yoghurt, beans and pulses, quorn, nuts and seeds are all good examples of protein rich foods.[1] 

Contrary to popular belief, using purely plant based proteins is a perfectly acceptable substitute for meat based sources, as combining them means all the amino acids are represented. Studies have repeatedly shown that a diet based purely on plant foods that meets energy requirements will meet all essential amino acid needs![2] Thankfully nowadays there are many options for non-dairy or non-meat protein sources. To give a few examples;  Pulses are an inexpensive protein choice, are high in fibre and a source of iron. They are part of the legume family and include all beans, peas and lentils. A daily serving helps to lower your cholesterol level and counts toward your 5-a-day.[5] Soya beans are another great option as they are a complete protein, comparable in quality with animal protein.[5] Like other pulses, they are low in fat and contain fibre and iron.[5] In addition, nuts provide a good dose of protein in a handful and are packed with fibre.[5] Although they are high in fat, and hence calories, most of this fat is heart-healthy unsaturated fats.[5] Like nuts, seeds also contain healthy unsaturated fats and protein.[5] As well as these, wholegrain breads, rice and pasta have more protein, fibre and iron than white versions.[5] For those who take part in certain sports activities or work out often, it may be beneficial to take protein supplements as well (e.g strength athletes), and there are many plant based options for those as well.[1]

In summary, protein is an essential part of a healthy life, and ensuring the body gets enough is extremely important. The range of proteins perform so many different functions throughout the body, so making sure these continue is of high priority. As there is such an abundance of foods that contain a good amount of protein, getting the 45-50g that is needed per day is deceptively simple. And for those wishing to cut down on their meat and/or dairy consumption, the wealth of plants containing protein provides a great alternative without having to sacrifice the quality. 

1) Sport and exercise: Food Fact Sheet [Internet]. British Diabetic Association. 2017 [cited 17 May 2021]. Available from: https://www.bda.uk.com/resource/sport-exercise-nutrition.html

2) A practical guide for dietitians [Internet]. British Diabetic Association. [cited 17 May 2021]. Available from: https://www.bda.uk.com/uploads/assets/61ad81e4-ea30-41d3-a03717a2467754d9/Practical-guide-other-sources-of-PROTEIN.pdf

3) Protein [Internet]. British Nutrition Foundation. 2021 [cited 17 May 2021]. Available from: https://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/protein.html?limitstart=0

4) Nutrition for Sport and Exercise [Internet]. British Nutrition Foundation. 2021 [cited 17 May 2021]. Available from: https://www.nutrition.org.uk/healthyliving/an-active-lifestyle/eating-for-sport-and-exercise.html?start=2

5) How to get protein without the meat [Internet]. British Heart Foundation. 2021 [cited 17 May 2021]. Available from: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/nutrition/protein/how-to-get-protein-without-the-meat

6) Protein [Internet]. Wikipedia. 2021 [cited 17 May 2021]. Available from: https://en.wikipedia.org/wiki/Protein

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