With carbs being described as the root of all evil, fats having to work hard on their reputation, it seems protein may have just got off scot-free. The gym community in particular seems terrified at the thought of not getting enough protein and there’s a common belief that there is ‘no such thing as too much’ when it comes to gaining muscle.
Although there is nothing wrong with consuming protein, as I have previously discussed, eating too much of anything will result in weight-gain.
With nutrition, nothing works in isolation and there is no one size fits all solution. How much protein you will need depends on a number of different factors. Protein is just as (in)capable as carbohydrate and fat in making you magically gain or lose weight.
What is protein and why do we need it?
Unlike carbs and fat, protein is not primarily used as an energy source. Protein is used as a building block for tissues, hormones and enzymes, and plays a vital role in regulating every process in your body. There’s a name for protein deficiency: ‘kwashiorkor’ and it is often found in regions where people suffer from famine. It causes the belly and limbs to swell due to excess fluid retention. In the Western world it is safe to say protein deficiency is not a problem. As long as you are consuming enough calories, you’re probably consuming enough protein.
Dietary protein is broken down into amino acids in the digestive tract for absorption. There are 20 amino acids of which 9 are essential meaning your body cannot make them so you need to eat them. Food sources are considered a complete protein if they have all 9 essential amino acids in the right amounts. Complete proteins are more often found in animal foods but it’s not impossible to get these from plants. This is where the famous beans and rice combination comes from. On their own, rice and beans only provide some essential amino acids, but together they form a complete protein, providing all 9 essential amino acids.
Your body has so many important uses for protein that it will only use protein as an energy source if there’s too much of it. The atom that sets protein apart from carbohydrate and fats is nitrogen. If protein is used for energy supply, the nitrogen part is split off from the molecule and excreted through urine as urea. This is where the myth comes from that you can eat as much protein as you wish because any excess protein will not be not metabolised, as you will wee this out. This unfortunately is a myth as the carbon skeleton that is left will supply energy just as much as the carbohydrate.
Protein turnover and Muscle Protein Synthesis
Our bodies constantly build up and break down protein, this process is called ‘protein turnover’. Depending on the function of the protein, its lifespan will vary. Enzymes and hormones function as messengers to control other variables in the body that can change rapidly, so their life span tends to be short.
Structural proteins for example in connective and muscle tissue have a longer life span. Most amino acids will be synthesised to new proteins depending on the body’s needs. However, the process of protein turnover is not 100% efficient and some amino acids are inevitably lost. That is why we need to eat protein, but the total amount of protein that is converted every day is much more than what we need to eat.
If more protein is synthesised than broken down, we say Muscle Protein Synthesis (MPS) is positive and we’re in an anabolic state. If more protein is broken down than built up we are in a catabolic state and losing protein. Muscle Protein Breakdown (MPB) therefore exceeds MPS. Important to note is that both processes are happening all the time simultaneously, but it’s the net balance over a period of time that matters.
Protein turnover is what allows our bodies to adapt to any stress you put it on. It’s what allows us to build muscle and for children to grow. However, the turnover of skeletal muscle is slow. The turnover rate of skeletal muscle is only 1-2% per day. Therefore, unfortunately there’s no point in eating excessive amounts of protein to stimulate muscle growth, because there is a limit to how much of it can be used for MPS.
Factors that impact Muscle Protein Synthesis
MPS is driven by two main factors: food, or more specifically protein intake and physical activity. Physical activity tends to have the biggest impact, but combined with protein consumption results in a more dramatic increase in MPS than either of these factors would alone. Resistance training provides the stimulus. It creates increased muscle sensitivity to the uptake of amino acids. Protein consumption provides the building blocks to facilitate growth. This is why just eating protein will not make you gain muscle. Unless the muscle is stimulated to grow, the nutrients are not put to that use. The protein balance is furthermore influenced by the following factors:
Age: as we age we lose muscle tissue. With age, MPB increases. This is called age induced sarcopenia. This process cannot be stopped but it can slowed down significantly with training and diet.
Illness/injuries: when we are dealing with the stress of illness MPB is increased. Some diseases induce muscle wasting, such as cancer and HIV.
Energy balance: when we lose weight some muscle tissue is also broken down. Muscle is an expensive (read: needs lots of calories to be kept alive) tissue, therefore if the body thinks it’s starving it will try and be as economical as possible with the available calories and having lots of muscle is not something that fits with that.
Exercise: resistance training leads to increased MPB. Despite this stress being used to build muscle right after training, MPB will be increased.
Due to exercise leading to a catabolic state it makes sense to assume that the best time to eat protein is right after training, when protein is required. The period after training has been coined the anabolic window of opportunity for that very reason. However, this increased sensitivity to amino acids can persist for up to 72 hours but the magnitude diminishes over time.
Much research has been carried out to determine its existence and duration with conflicting results. How experienced you are seems to be the determining factor. For novice lifters the window lasts much longer than experienced ones. Therefore, the recommendation is to have protein within 12-48 hours of training which is what most people would do anyway.
Timing of protein intake is of very little importance as long as the overall intake of protein is optimal for most. By this I mean the right amount and quality. The good news is there is no need to worry you’ll lose all your gains if you don’t down a protein shake straight after your workout!
So how much protein is enough?
How much protein is needed remains a topic of debate. The official recommended daily intake is 0.83 g/kg/day for sedentary individuals and for a long time this recommendation was no different for athletes. Only recently the ACSM has changed this recommendation to 1.2 to 2.0 g/kg/day for athletes, but some research suggests even higher intakes of up to 3.1 g/kg/day for resistance training athletes on a calorie restricted diet.
What the optimal amount is for you depends on your body size, your goal and activity level, but also your training status. For example, trained athletes need less protein than someone who’s just started lifting. This makes sense because the more you practice something the better our bodies adapt to it. The trained individual will have less MPB after each session because their body is used to it. They will also be closer to their maximum muscular potential than someone who has never touched a weight in their life. There’s much more room for improvement when you’re just starting out.
Most studies carried out on athletes and muscle gain suggest there is no added benefit of eating any more protein than 1.6 g per kg bodyweight, 1.8 g per kg body weight is the upper limit to which an excessive intake doesn’t lead to more gains. This is not to say a higher intake is damaging (unless you have kidney problems) as we eat protein for reasons other than muscle gain. Protein satiates and many people find it tasty. However, when it comes to muscle gain, research has not shown a benefit of having 2.8 g per kg over 1.8 g per kg.
To recap: Protein is not primarily used as fuel, but rather as a building block for tissues, muscle, enzymes and hormones. Protein in the diet is broken down to amino acids to be absorbed in our guts and it is the type of amino acids that makes one protein of better quality than the other. Protein is constantly built up and broken down in our bodies, when MPS exceeds MPB we gain muscle mass, if MPB exceeds MPS, we lose it. MPS is determined by 2 main factors: protein intake and resistance training. Even though recommendations can vary a lot per individual, for muscle gain there is no added benefit of having more than 1.8 g per kg bodyweight per day.