This is the first of some shorter blogs, with some quick thoughts that might interest you on a variety of nutrition topics. First up is the importance of eating protein!
What is protein?
The Protein we eat (and by extension the amino acids it provides) is commonly referred to as building blocks for the body and whilst this is somewhat true, this short article will explain some other functions of protein. How it helps us perform, grow and function throughout our lives and how much you might want to aim to eat per day.
For us to understand protein and what it does, we need to start by looking at the most basic component of protein:
Amino acids. These can be categorised as essential and non-essential, as listed in the table below:
Essential | Non-Essential |
Histidine | Alanine |
Isoleucine ☥ | Arginine* |
Leucine ☥ | Asparagine |
Lysine | Aspartic acid |
Methionine | Cysteine* |
Phenylalanine | Glutamic acid |
Threonine | Glutamine* |
Tryptophan | Glycine* |
Valine ☥ | Proline* |
| Serine |
| Tyrosine* |
*Conditionally essential amino acids: certain people and disease states may be required to take these in through diet to support their needs.
☥ Branched-chain amino acids: function to stimulate protein synthesis and act as a fuel source during exercise and low energy availability.
A simple way to look at it is that essential amino acids need to be taken in through the diet, and non-essential can be made by the body. All amino acids have a role in bodily functions. For example, one role of cysteine is as a component of the antioxidant glutathione, tyrosine is used as a neurotransmitter and for adrenal function. The full complement of essential aminos is required for tissue growth and repair of muscle tissue.
The source of protein is an important consideration, animal protein sources will contain the full amino acid spectrum, we are talking: Fish, dairy, meat and poultry when we typically think of animal protein. Plant protein sources typically lack one or more of the essential amino acids. Though this has historically been seen as a problem, by combining planting sources within meals and throughout the day, you can complete the amino acid profile, making them just as valid an amino acid source as their animal counterpart.
Here’s a great example: Rice tends to have a decent amount of protein (7-8g/100g) but is lacking lysine, it can be combined with kidney beans (8-9g/100g) which contain and contribute lysine to the meal. This type of meal illustrates this synergism further, as the kidney beans lack methionine, which is coincidentally present in the rice, so a meal of 100g of each provides 16-18g of complete protein.
The diagram below can help you select plant protein sources within meals and throughout the day. If you are omnivorous, I would usually encourage you to include some of these sources too, eating more plants in general is healthy, but you don’t need to consider combining sources.
What does protein do?
When most people think of protein, they see sweaty guys with big muscles working out in front of a mirror. Whereas muscle growth is certainly one of the main functions of proteins (and by extension the amino acids they provide), there is a wide range of functions throughout the body that rely on protein to function. In fact, you may see protein and amino acids referred to as “building blocks” for the body, but they are more like cogs in a machine. They are essential for the function of enzymes, neurotransmitters, receptors, digestion, immune health, concentration, mood, memory, stress responses, sleep, hormone production… this list goes on!
So…. How much?
Now we’re on to the golden question. How much protein do we need, and can you eat too much?
The recommended daily allowance for protein is typically 0.8g/kg. That way, if you weigh 50 kg, you’ll need 40g per day. This was suggested to help maintain muscle mass as we age, and indeed this is a good starting point for anyone getting started in including protein in their diet. More recent research, however, has shown that a higher protein intake (<1.2g/kg) may be more beneficial, especially in elderly and active populations, which should be eaten at regular times throughout the day (every 3-6hrs). To effectively switch on protein synthesis, most people would need between 20 and 40g per meal. This varies depending on several factors such as age, calorie intake and body weight.
The amount of protein you eat can (and arguably should) go higher still if you exercise, are dieting or plant-based. Let’s break down why and how much…
Exercise
When we exercise, we damage and accelerate the breakdown of our muscle tissue and stimulate our muscles to repair, remodel, adapt and grow. This is true for both aerobic and resistance training. Although, _what_ gets grown and adapted is influenced by the type of exercise we do. Resistance exercises like weight training typically emphasise growth in muscle size and strength, whereas aerobic work like running causes the muscle to make and repair mitochondria, making us more aerobically efficient.
Both of these processes require protein, and to keep our muscles repairing and remodelling properly we need to eat more protein to support it. Typically, athletes and regular exercisers are encouraged to eat 1.4-1.6g/kg of protein per day.
Dieting
Along with exercise, dieting or being in an energy deficit can also increase your need for protein. The body’s response to a calorie deficit is to conserve as much energy as possible, especially if that deficit is large. Muscle tissue and metabolism take a lot of energy, and the body will break it down if it's not used. Especially in a deficit. It will become harder to stimulate muscle repair and growth when there is less overall energy to maintain the tissue. By increasing protein intake, you reduce the amount of muscle tissue lost and maybe (maybe) even eek out some growth. You’re looking at from 1.6g-2.6g/kg to preserve tissue here.
Plant-based eating
As I said earlier in the article, times have changed, the science is being done, and the view towards plant proteins is improving. Indeed, recent research has shown that plant-based proteins can be just as effective as animal proteins at stimulating muscle growth, making it a very valid option for anyone pursuing a plant-based lifestyle or looking to reduce their animal intake.
There are a few things to consider for plant proteins that may not be immediately obvious. On top of making sure you get a complete amino acids profile throughout the day as discussed above, making sure to eat enough of the branch chain amino acids, especially leucine, is an important consideration. Not all plant sources contain the same levels of amino acids, so it is wise to include a range of sources throughout the day, with an eye on when you consume them. Leucine is a vital nutritional stimulator of protein synthesis and muscle growth, so choosing high leucine-containing sources such as corn, pea, or potato around your workout is prudent. It is also worth considering that plant proteins may not digest or absorb as well as animal proteins and therefore, aiming for a higher intake of <1.6g/kg is recommended.
It is also worth bearing in mind that supplementing _might_ be a more pressing consideration if you are plant-based. Especially if you are dieting or have physique and performance goals. Plant protein is often coupled with an amount of carbohydrate, which could rapidly increase the calorie burden of your diet when trying to hit 1.6g/kg of protein. In this case, it may be useful to use a plant-based protein powder or Essential Amino Acid supplement in the workout window (either before, during and after training).
So there we have it, a quick overview of protein. What it is, where to find it and how much! There’s a surprising amount of nuance when it comes to protein, and the context you look at it in is important to consider. I hope you’ve enjoyed this article, and it's given you some food for thought (ha!) I’m always happy to answer any questions you might have in the comments.
References
Lonnie, M., Hooker, E., Brunstrom, J. M., Corfe, B. M., Green, M. A., Watson, A. W., Williams, E. A., Stevenson, E. J., Penson, S., & Johnstone, A. M. (2018). Protein for Life: Review of Optimal Protein Intake, Sustainable Dietary Sources and the Effect on Appetite in Ageing Adults. Nutrients, 10(3), 360. https://doi.org/10.3390/nu10030360
Jäger, R., Kerksick, C.M., Campbell, B.I. et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr 14, 20 (2017). https://doi.org/10.1186/s12970-017-0177-8
Phillips SM, Van Loon LJ. Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci. 2011;29 Suppl 1:S29-38. doi: 10.1080/02640414.2011.619204. PMID: 22150425.
Hevia-Larraín V, Gualano B, Longobardi I, Gil S, Fernandes AL, Costa LAR, Pereira RMR, Artioli GG, Phillips SM, Roschel H. High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet to Support Resistance Training Adaptations: A Comparison Between Habitual Vegans and Omnivores. Sports Med. 2021 Jun;51(6):1317-1330. doi: 10.1007/s40279-021-01434-9. Epub 2021 Feb 18. PMID: 33599941.