How Much Protein Should You Eat?
Updated: Nov 28, 2018
When you hear 'protein', what do you think of?
Bodybuilders, protein shakes, the gym, huge steaks, this guy?
Let's start with the basics - here are some basic protein facts:
Protein is one of the 3 macro nutrients (alongside carbohydrates [article coming soon] and fats [article coming soon]), and is made up of amino acids joined by peptide bonds.
Protein contains 4 calories per gram- so 25g of protein contains about 100 calories (bear in mind that almost every food that we eat is not pure protein, it will also contain some combination of carbs and fats)
Proteins and amino acids are essential for the growth and repair of the body, including muscles of course, but it is also a crucial structural component of tissues and cells throughout the body such as bones and skin. In addition, protein is crucial for cell signalling (the process whereby cells send messages to the brain), for hormone production, for providing enzymes that kick off chemical reactions in the body and for immune function. Oh, and it can also be converted to glucose in the body via a process called gluconeogenesis.
[To skip to Take Home Points, scroll to the bottom]
Protein is clearly essential in the human body, but in recent years has sometimes had negative press coverage, particularly with the onset of the vegan trend (and its awful Netflix documentaries), and with poorly headlined news articles such as this from the BBC, which took much of the information from their experts out of context (including Professor Graeme Close, programme leader for the Masters degree in Sport Nutrition at LJMU, who in fact says 'I believe most need more than the recommended daily allowance, and there’s good evidence to support this,” and Kevin Tipton, Chair in Sport, Health and Exercise in Sport at the University of Stirling, who tweeted:
So what is the truth about protein - how much should you really eat?
The slightly annoying answer is the same as with many nutrition questions - it depends!
The main factors that influence how much protein you require as an individual are:
Your size and weight
Your body composition (muscle - fat ratio)
Your goal - are you trying to lose weight, gain weight or maintain weight?
Your activity levels
Your need/desire to adapt - are you merely surviving, or are you trying to optimise your body's ability to adapt to some form of physical training?
If you are training, what is your type of training - is it muscle growth (hypertrophy) or endurance-based, or is it some mixture of both? (And therefore falls somewhere along the continuum between pure hypertrophy and exclusively endurance)?
Food restrictions (eg. degree of vegetarianism)
Clinical restrictions (eg. kidney disease status)
We will pick up on a few of these in more detail.
Firstly, as we know, smaller people need less food overall to acheive maintainence calories [remember 'Calories are King'], while larger people need more. This of course translates to protein intake, so the overall total amount of protein will usually be larger for a larger person.
Therefore, when talking about how much protein a person needs, in order to mitigate for people's varying weights, we express protein consumption as a proportion of bodyweight. We will therefore use a measure of grams of protein per kilogram of body weight (g/kg). [some of the more recent studies have used a more accurate measure - g/kg of lean mass, aka fat free mass, measured by taking a person's total body mass and taking away the amount of fat mass. While this is ideal, we don't always have this information, so using total body weight, or even target body weight, is an acceptable compromise].
As we mentioned above, your exact g/kg requirement will depend on a variety of factors, but fortunately there have been several studies which have looked at how those requirements differ.
The current recommended daily intake for adults who are minimally active is 0.8g/kg of body weight.
Several studies have suggested that higher amounts should be recommended, particularly with increasing activity levels, and there is a general upwards trend amongst the scientific literature for the recommended daily protein intake. However, the recommended daily intake for 'healthy' (meaning disease free, rather than in optimal health), sedentary adults have yet to be amended.
It is worth bearing in mind, however, that this recommended daily intake is only to prevent a protein deficiency - so it's the minimum amount needed to avoid malnutrition (which is pretty serious!).
We need more than this to function at our best, including good immune function, metabolism, satiety, weight management and performance. In other words, we need a small amount of protein to survive, but alot more to thrive. The recommendation for health purposes would therefore be between 1.2g/kg and 1.6g/kg, increasing if the person is more active.
In the long term, the main consideration for optimal health is that the majority of your diet comes from real food (not ultra-processed foods, which are usually high sugar, high fat, low fibre, low nutrient foods). [remember to Eat (Mainly) Real Food].
Another consideration is that protein levels fluctuate during the day. This means that moderate amounts of protein consumed at regular intervals is necessary. Basically, you should aim to eat protein with every meal, and most snacks, rather than just one huge hit of protein that maxes out your daily intake in one go.
As we learned in 'Core Principles', fat loss requires a calorie deficit.
Strictly speaking, as long as you are in a calorie deficit, your protein intake doesn't matter.
However, protein can be helpful for fat loss in a number of ways.
Firstly, protein is the most satieting (filling) macronutrient, so we feel fuller for longer when we have a higher protein intake in each meal. The main reason is that protein has a double-edged effect of boosting the "fullness hormone" peptide YY, and decreasing the "hunger hormone" ghrelin in your body.
Being fuller means we are less likely to overeat, making it easier to achieve the calorie deficit that we need for fat loss. Indeed, the research shows that a higher protein intake is associated with a lower overall calorie intake, so increasing the proportion of the diet that is made up of protein usually results in eating fewer calories overall, meaning more weight loss.[see https://www.ncbi.nlm.nih.gov/pubmed/16002798 for another example].
As well as the effect on appetite, getting enough protein means that you lose fat tissue, rather than muscle mass, since protein preserves muscle mass while you diet. The preservation of muscle mass also preserves your metabolism, since in general, the more muscle mass you carry, the higher your metabolic rate (the rate at which you absorb the food you eat).
In order to make the most of protein's potential benefits for muscle mass, you should also do some resistance training (lifting weights).
In summary, getting enough protein, whilst in a calorie deficit, means you lose fat, not muscle - you will look better, feel better and live longer.
So how much is 'enough protein' when fat loss is the goal?
This is slightly difficult to answer, as once again, the amount a person needs will be dictated by the factors above. Again, protein intake doesn't strictly matter, provided you are in a calorie deficit.
However, the literature seems to suggest that between 1.4g/kg and 2.2g/kg can be optimal for fat loss.
As a starting point, if you aim for the middle to upper end of this range (1.8g/kg and above), you can start to get a feel for what that actually looks like on a plate across the day, and you can adjust up or down if necessary, depending on satiety, how you feel, and how easily you can stick to a calorie deficit.
[For those aiming to lose massive amounts of fat, we can also use 1.8g/kg of the person's target weight. Adoption of this technique is very personal, so should only really be done under the guidance of a nutritionist.]
This is where measuring your food comes in handy, whether by using MyFitnessPal, using your palms to approximately measure portion size, or simply keeping a food diary with your nutritionist. Whatever your method, tracking your protein (and calories - link to fat loss article), will be extremely useful in managing your diet going forward. You don't need to do it forever, but being able to measure your food intake is a useful 'tool in your box', and can come in useful in several situations.
For gaining muscle, protein is obviously a crucial component of the diet (muscle gain article coming soon).
How much protein you should eat to maximise muscle protein synthesis (MPS) has been a long-running topic for debate within nutrition research (particularly in bodybuilding circles). Controversy still exists about minimum and maximum amounts of protein, how much protein is optimal, and how much the body can use for muscle building.
The most recent meta-analysis suggested that, as a minimum, protein intake for muscle building should be 1.6g/kg, which should be split across the day. They also found that in a single meal, the body has a 'minimum effective dose' of protein to facilitate muscle building (this is also known as the 'leucine threshold' - leucine is the amino acid that 'triggers' muscle building, and the source of protein should therefore have a high leucine content). This minimum effective dose was found to be 0.4g/kg, meaning that for muscle building, every meal should have at least this amount of protein (for example, an 80kg male looking to build muscle should aim to eat at least 32g of protein per meal). If only this amount is consumed in a meal, the person would need to eat four meals a day in order to hit the suggested 1.6g/kg minimum.
A study by Eric Helms on bodybuilders found that 'most but not all bodybuilders will respond best to consuming 2.3-3.1 g/kg of lean body mass [i.e. not including fat mass] per day of protein'.
The recommendation would therefore be to aim for between 1.8g/kg and 2.2g/kg for muscle gain, and ensuring that each meal contains at least 0.4g/kg of protein (as an example, three meals a day to hit 1.8g/kg total protein per day would require 0.6g/kg protein per meal, while four meals a day to hit the same daily 1.8g/kg would require 0.45g/kg protein per meal). Again, this is about finding what works for you.
Other Circumstances that increase protein requirements
As the human body ages, muscle tissue will often start to break down (a process known as muscle atrophy), leading to losses in strength, disability, losses in mobility, increased hospitalisation and decreased independence.
The recommended daily allowance of 0.8g/kg is insufficient for ageing adults, and the evidence points to increasing protein intake as you age to prevent sarcopenia (age-related muscle wastage), since muscles of the elderly become resistant to normally anabolic stimuli. The experts in protein and ageing recommend an intake of between 1.2g/kg and 2g/kg.
Again, aiming for the middle of the range may be a good starting point.
Injury requires the rebuilding of tissues. Depending on the type of injury, this may mean that the person is unable to train or exercise in their usual way. This may necessitate a slight decrease in overall calories during the day (due to fewer calories being burned through exercise), but protein should be kept higher than usual to facilitate the repair of the tissues. Higher protein intakes (around 2g/kg - 2.5g/kg per day) are therefore recommended during periods of immobilisation due to injury.
Performance athletes (whether strength, speed, endurance or some combination of these) require high protein levels in order to help muscles repair and regrow. The International Olympic Committee Consensus on Sports Nutrition recommends that strength and speed athletes consume at least 1.7g/kg of protein, with up to 2.2g/kg also being efficacious.
This level of protein requirement also translates to endurance athletes, who require high daily protein levels in order to prevent muscle breakdown during and after exercise. ;
If you are performing in any sort of sport, it is therefore a good idea to get a minimum of 1.7g/kg of protein.
Myths About Protein
'Too much protein is bad for your kidneys/causes kidney disease'
This is a long-standing myth that persists in the minds of many people.
There have been numerous studies on this, even on populations who are at higher risk of kidney disease (dyslipidemia, obesity, hypertension), and they have found no evidence of any detrimental effect of high protein intakes on kidney function for those without existing conditions.
In fact, weight loss reduces the risk of having poor kidney (renal) function, and we have already seen the benefits of protein for fat loss (above).
For those with existing chronic kidney disease, reducing protein is one of the ways of reducing the strain on the kidneys, but for people free of kidney disease, there are no detrimental effects of eating protein.
'You can only digest 30g of protein at one time'
This is false. There has been no upper limit discovered, as the body will slow down digestion in order to absorb all the nutrients it is given. This 'upper limit' myth is based on misinterpretations of research.
However, as we mentioned before, protein levels naturally fluctuate during the day, so aim to eat protein with every meal, and most snacks, rather than just one huge hit of protein that maxes out your daily intake in one go.
'High protein diets create diabetes, heart disease, cancer'
This is a direct quote from 'What The Health', and is misleading at best, dangerous at worst. Protein has all the health benefits that we have been through above - benefits for fat loss (bringing with it a reduced risk of diabetes, heart disease and cancer), maintainence, repair and growth of muscle, bone and skin tissues, cell signalling, hormone production, enzyme provision and immune function.
People with diabetes, heart disease and cancer do not have those diseases because of excessive protein. There are a number of contributory factors, but the most common are: eating too many calories, too many processed foods, not enough real foods, too many trans fats etc.
Please do not go to Netflix for nutrition advice.
Real Considerations for Protein Consumption
Protein Quality The quality of the protein you eat affects the ability of the body to utilise it for repair of tissues, immune health and all the other benefits we listed above. The main factors determining the 'quality' of a protein source are: Digestability - i.e. how easily our bodies can absorb the protein source.
Other nutrients found in the protein source - meaning vitamins and minerals, fibre, etc
Amount of essential amino acids (meaning amino acids that our bodies do not produce naturally, and which are therefore required from the diet).
Of the essential amino acids, leucine appears to be the most important in terms of triggering muscle protein synthesis, thereby repairing and preserving muscle mass (hence the minimum amount of protein per meal being referred to as the 'leucine threshold' in the Shoenfeld study we mentioned above)
Proteins with high levels of each essential amino acid are known as 'complete' proteins. Those with lower levels of some essential amino acids are 'incomplete'. The good news is that the best amino acid profiles are found in natural sources of protein - meat, fish, dairy and eggs. Most plant sources of protein, however, are incomplete proteins, meaning that a variety of protein sources is needed in the diet to get a full amino acid profile.
High amounts of protein without sufficient fibre in the diet can lead to gut health issues (gut health article coming soon), which can in turn lead to other health issues.
It is therefore important to consume sufficient fibre in the diet from whole food sources such as vegetables, fruits, legumes and whole grains.
The BBC article I referenced earlier (scroll up) was really about supplements, in spite of the headline.
The supplement industry is huge, and whey protein in particular has exploded in popularity over the last decade.
As we mentioned, whole food sources of protein have the best amino acid profile, as well as containing other nutrients that contribute to overall protein quality, and therefore have a beneficial effect on our health.
Whey protein (specifically whey protein isolate) also has a 'complete' amino acid profile (including a high leucine content), hence the popularity of whey protein.
Because of the relative lack of process involved in producing whey (it is one of two proteins present in milk (the other being casein), which is simply dried into powder form), there is some debate as to whether why protein should even be called a 'supplement', or whether it can simply be considered a food.
The main benefit of whey protein is convenience. A whey protein shake is quick and easy to knock up, you can carry it around with you, and for a lot of people, is a lot more convenient than preparing a whole food meal.
We would always advocate having a whole food meal, mainly for the overall veriety of nutrients, but whey certainly has it's place as a convenient alternative protein source.
One thing to look out for on the supplement front is marketing scams. Whey protein isolate is the highest quality whey, with little to no added extras. Once you start moving away from Whey protein isolate, more and more additives are added to protein products.
Make sure you read the label of any protein product that you buy. There is no best protein for women, for fat loss, for bulking, for anything - whey protein is whey protein, regardless of packaging, or extra ingredients. If you do purchase a product with extra ingredients, ask yourself whether these are actually going to help you reach your goal. If you don't know, don't buy it! You can always start with whey protein isolate, and add extras yourself that you know will actually help you.
Lots of companies have jumped on the bandwagon of protein, and you can now find Protein Weetabix (actually only has one gram of protein more than regular Weetabix, and the overall protein content is still pretty low), Protein Mars and Snickers bars (19g of protein, 200-ish calories) and a myriad of other products claiming to be 'high in protein'.
As with everything, make sure you read the label, including the numbers for the portion size, not just the amounts per 100g.
Most of these products will be highly processed, and therefore nutritionally inferior to a whole food meal, but if you need a convenient snack, and it fits with your goal (in terms of overall calories, other nutrients etc), then these may be a good option.
One supplement that has received some coverage recently is BCAA supplementation. We mentioned BCAAs before (branched chain amino acids), and the logic behind their development as a supplement was based on the discovery that the body couldn't produce them itself. However, there are no proven benefits to taking BCAAs as a supplement on their own, since the availability of other essential amino acids will be a limiting factor.
The best way of ensuring you have sufficient BCAAs is to get them from food (including whey, meat, fish, dairy, eggs etc), so don't bother with BCAA supplements.
Protein for Vegans
I've written a separate article on protein for vegans [here].
Take Home Points
Protein is crucial for the growth and repair of the human body, including muscle, bone, skin and connective tissue, as well as hormone and enzyme production.
Protein is beneficial for fat loss, mainly because of satiety (fullness) and preservation of muscle mass
Protein is beneficial for muscle gain, and recomendations of daily protein intake to maximise muscle protein synthesis are between 1.8g/kg and 2.2g/kg
Protein quality is determined by digestability, vitamin and mineral content, and amino acid content
Leucine is the most important amino acid for muscle protein synthesis, and should be present in every meal (at an amount of at least 0.3 - 0.4g/kg).
Meat, fish, dairy and eggs all have high leucine content.
Vegans may need to consider protein supplementation and/or relevant food combinations to ensure appropriate intake.
Protein requirements increase for elderly populations, those with injuries, and performance athletes
Whey protein is a convenient protein source, but be wary of added ingredients and calories in some 'protein' products
There are no risks to kidney health associated with protein. There is no 'upper limit' of protein per meal. Claims about protein expressed in 'What The Health' are complete rubbish.
Your exact personal requirement of protein will depend on several factors and will vary day to day.