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Protein is one of the macronutrients we hear about frequently, especially being mentioned in connection to sports. We see people walking around in the gym with protein shakes and interestingly, the shelves of "health shops" such as Holland & Barrett are always packed with protein snacks and bars. We are told by personal trainers that we should have a lot of protein and possibly right after training. But what is all this hype about? What is protein and why does everyone in the fitness world seem to be so obsessed about it? Is it really this crucial? Is it a miracle macronutrient?
What is protein? (the sciency bit)
Protein is a macronutrient, which means that we need it in large quantities in our diets.
It is a primary nutrient for the body, responsible for growth, repair and maintenance of body structures and tissue. This is why we talk so much about it when it comes to physical activity.
Amino acids are the building blocks of protein - some of these, more specifically 9 are essential, which means that we cannot manufacture them in the body, we must get them from our diet. These are only found in animal sources. Complete proteins are the ones that contain all essential amino acids in correct proportions, which is the most beneficial for our bodies, such as meat, milk, cheese, eggs.
The only plant source of complete proteins is soy.
However, we can create complete proteins by combining some incomplete forms such as legumes and grains, like beans and quinoa or rice. Good plant sources of protein are pulses and legumes, nuts, spinach, broccoli, mushrooms and all soy products.
Other crucial roles of protein are being involved in making specific hormones such as insulin, it may also act as enzymes, helping chemical processes such as digestion. It helps the immune system's functions by creating antibodies and immune cells that protect the body from infection and disease. It can also be used as a source of energy, however being so versatile and crucial, it is best to get a source of energy from carbohydrates and fats to preserve protein in the body.
How much do we need?
The simple answer is always: It depends. In reality, there are many things to be taken into consideration when working out how much protein to have.
The NHS recommends 50g of protein per day for adults. The British Nutrition Foundation's recommended amount of protein is 0.75g/ kg of body weight per day, which for a 70kg person would be 52.5g per day.
However, here comes the complexity of nutrition. It is important to remember that the amount of protein intake also depends on activity levels, age, gender, health status etc, so these values are only estimates for the population and not personal guidelines to follow. Emotional and physical stress, infection, post-surgery recovery and trauma also require higher amounts of protein, so that the body can heal and repair.
Athletes generally have higher protein requirements than non-active people. During and after exercising the use of muscles cause micro-tears in them and extra protein is needed to compensate for this increased muscle breakdown and to build new muscle cells. The recommended amount of protein for athletes by the ACSM (American College of Sports Medicine) is between 1.2g and 2g of protein per kg of body weight.
If you are less active or are a recreational exerciser at low-moderate exercise intensities a couple of times a week with shorter training bouts than an hour, there is likely no significant increase in your protein needs.
Let's put all this into context
By now we know that protein helps with muscle repair and growth, so maybe we understand a bit better why trainers and the fitness world are slightly obsessed with it. It is without a doubt a really important macronutrient, but all this does not make it a miracle macronutrient. We can definitely let go of glamorising it so much.
We also know that if we are physically active, we need to have more protein than a sedentary person. The amount will depend on many factors and is personal to everyone.
Also, as mentioned above, we know that we can use protein as a source of energy if we deplete our muscle glycogen stores (glycogen in the muscle is used as a primary energy source during exercise), which typically occurs after 60-90 minutes of endurance exercise, for instance after a long run. We would definitely like to avoid this, which we can do with adequate pre-training fuelling with carbohydrates. Post-training we can also help our body to recover properly and replenish our stores by having protein together with carbohydrate. This will help to repair muscle and building new tissue.
Resources:
The British Nutrition Foundation (2018) - Protein
National Health Services (NHS) (2020) - Reference intakes explained
Anita Bean (2017) - The Complete Guide to Sports Nutrition. Bloomsbury Publishing Plc
James Collins (2019) - The Energy Plan. Penguin Random House UK
William D. McArdle, Frank L. Katch, Victor L. Katch (2007) - Exercise Physiology: energy, nutrition, and human performance. Lippincott Williams & Wilkins