How much protein do I need to help me reach my goal(s) is a question many people are often left pondering. Dietary protein intake is one aspect of a diet that is surrounded by controversy, with much confusion, particularly amongst the general public, about how much protein is needed or required to meet goal(s). This uncertainty isn’t helped by the bombardment of scare-mongering headlines so frequently advertised in the media regarding high protein diets. As a result, total protein intake, in addition to considerations regarding protein quality and protein distribution (on a per meal basis), is often overlooked.
Not surprisingly, many people still believe that diets high in protein can have detrimental effects on health. The most commonly cited claims often revolve around kidney failure and reduced bone health.
Note – despite persevering beliefs to the contrary, there is no evidence-based link between higher protein diets and renal disease (in individuals with normal renal function) or adverse bone health.
In fact, it has been suggested that dietary protein intake (particularly dairy protein) is supportive of bone health, when vitamin D and calcium intakes are adequate, in addition to a number of other protective effects associated with human health. Furthermore, an increase in dietary protein has also been linked to a reduced risk of osteoporosis and fractures in old age.
What does dietary protein do?
Protein’s primary role in the body is to promote growth, development and to help repair cells. Protein has a high thermic effect, meaning it requires a large amount of energy to break it down and digest. As a result, there is a metabolic advantage to a high protein diet when compared to a normal diet, meaning a high protein diet may increase the amount of calories ‘burned’ by 80 – 100 kcals per day.
Once ingested, protein is broken down into its constituent amino acids. Amino acids are often referred to as the ‘building blocks’ of the cell and can be absorbed by the small intestine to be transported in the blood. Protein plays a part in numerous processes within the body, including, but not limited to: bone health, muscle mass maintenance, immune function and stimulation of protein synthesis.
The term ‘protein quality’ mentioned at the start of this article refers to the amino acid profile, the digestibility of the protein to release the amino acids for absorption, and the availability of the absorbed amino acids for protein synthesis.
Animal-based proteins have a denser amino acid profile leading to a lower energy (calorie) content when compared to plant-based proteins. This may be of practical relevance for those looking to lose or maintain body weight given that animal protein sources allow for the greatest protein content with least calories.
How much protein do I need?
The current RDA (Recommended Daily Allowance) for protein for adults is 0.8 grams per kg of body weight per day (g/kg/day). This amount is defined as sufficient ‘…to meet the known nutrient needs for practically all healthy people.’ While the RDA ‘may’ meet the requirements for the average sedentary individual in energy balance, this is simply inadequate for athletes, the elderly and the dieting population.
Note: Recommendations regarding dietary protein intake need to be context-specific and individualised with respect to the population and goal(s). There also needs to be a distinction made between protein requirement and optimal protein intake.
Protein and fat loss
For those looking to lose weight, specifically body fat, a high(er) protein diet (>1.2g/kg/day) can facilitate retention of lean mass. In a recent study in postmenopausal women, individuals who consumed 1.2g/kg/day compared to those who consumed the RDA (0.8g/kg/day) retained almost 50% more lean body mass during dieting conditions (i.e. in an energy deficit). Although this was not the primary outcome of the study and both groups lost the same amount of total weight (10% of original bodyweight), these results illustrate the superior nature of the quality of the weight loss in the higher protein group i.e. more fat tissue loss and less muscle tissue loss. These results are consistent with many previous studies looking at protein as a dietary component and its beneficial effects on weight loss. More often than not, this can be seen as a positive result when we consider that muscle tissue is an important tissue in terms of whole-body metabolism.
Protein and Appetite
In addition to protein’s beneficial effects on the preservation of lean muscle tissue, a high protein diet (levels +50% greater than the RDA) can be used as a valuable tool to help with appetite control and regulate meal-to-meal satiety (i.e. to feel full following a meal).
Protein is known to have the highest satiating effect, per unit calorie, when compared to fat and carbohydrates. Therefore, the greater ‘feelings of fullness’ associated with a high(er) protein diet can lead to a lower spontaneous energy intake without active restriction of calories. Consequently, this can help reduce the temptations, often experienced when dieting, to make poorer food choices leading to overconsumption of calories, which can ultimately sabotage one’s diet / undermine any fat loss efforts.
A high protein diet can also have an effect on integrated systems within the brain that regulate body fat levels, which can play a role in maintaining body fat loss in the longer term.
This would suggest that a higher protein diet is not only beneficial when dieting but can also be an effective tool for weight maintenance and may facilitate an increased ability to remain at a reduced weight, once reached.
For these reasons, protein is one of the most powerful tools in the fat loss and weight management toolbox.
Protein and the elderly
Maintenance of lean muscle tissue and strength should be of primary concern particularly as we grow older. The age-related degeneration of muscle tissue, termed sarcopenia, can be modified with exercise (specifically higher-intensity aerobic training and resistance exercise) and with nutrition. Recommendations based on the latest research suggest that a greater emphasis should be placed on dietary protein levels, on a per-meal basis, that ultimately exceed the RDA guidelines. Considerations regarding muscle capacity and muscle function leading to the preservation of muscle mass and strength can greatly improve quality of life with advancing age resulting in a longer, healthier and improved lifestyle.
Guidelines suggesting a daily protein intake of 1.2-1.5 g/kg of body mass per day are safe and likely to help maintain muscle mass and strength for healthy older adults.
Protein and the athlete
In addition to the health benefits associated with a high protein diet, dietary protein also plays a crucial role in promoting exercise-induced adaptations to training and optimising recovery. Higher protein diets can therefore help maximise athletic performance, stimulating muscle protein remodelling after exercise.
Protein essentially allows us to adapt, acting as a substrate to augment the response to resistance training and support muscle protein synthesis, leading to an increase in muscle mass. Protein is equally as important for endurance athletes. Endurance exercise stimulates synthesis of other proteins within the body that improve adaptation and help an athlete to get fitter.
Research recommends anywhere between 1.2 – 3.1 g/kg total dietary protein per day for athletic populations depending on the type of athlete, specific goal(s) and training regimen.
Based on the mechanistic research available, protein considerations on a per-meal basis may be a plausible strategy, depending on the goal of the athlete (perhaps of greater importance to those seeking to optimise gains in muscle mass or improve body composition).
Although research views are mixed, protein timing can play an important role in an athletic population and consumption of a good quality protein source soon after (< 60 mins) training is a simple-to-follow strategy, helping to initiate the adaptive response. This strategy becomes more important where protein has not been consumed prior to the training session.
If, however, it is more convenient and suits personal preference to consume protein immediately before training, that, too, can have similar beneficial effects on muscular adaptations.
Is it possible to eat too much protein?
A recently published study provided further evidence that a diet high in protein does not cause harmful effects on kidney (or liver) function. The myth likely stemmed from the fact that individuals with kidney dysfunction are advised to go on low(er) protein diets for therapeutic reasons with the aim of improving renal function. It should be noted that there is little to no evidence that high protein diets are harmful to healthy people. In agreement with this, both the World Health Organisation (WHO) and the Institute of Medicine (IOM) state that there is no link between protein consumption and renal health.
This study showed that, during a year-long trial, resistance-trained males, consuming 3-4 times the RDA in terms of dietary protein did not display negatively affected blood lipid profiles, liver function or kidney function, amongst other parameters. The misconceptions linking higher protein diets and kidney damage in individuals without a pre-existing disease were not upheld.
Although, consuming a high protein diet does not directly lead to detrimental effects in terms of kidney or liver health, it is possible (albeit rare) to consume too much protein where this is at the expense of essential dietary fat requirements. Similarly, if a high protein intake leads one to overconsume calories resulting in a positive energy balance and subsequent fat gain, long-term health may be compromised. It is also possible to eat too much protein at the expense of carbohydrate intake, required to adequately fuel and support training and exercise sessions, particularly those at higher intensities. Similarly, protein intake can be deemed excessive if carobhydrate intake is restricted to a level that negatively impacts digestive health, metabolism, mood and sleep quality.
It is worth bearing in mind that dietary protein intake does not need to be overdone. Ideally, ‘how much protein do I need’ should be assessed on an individual level based on age, body composition, training requirements and goal(s) and NOT using a ‘one size fits all’ approach.
It is clear from the evidence that a protein diet higher than the RDA can be beneficial for the dieting population, for those who want to maintain weight loss and/or improve body composition, for the elderly, hoping to minimise age-related degeneration of muscle tissue, and for the athletic population seeking to maximise training adaptations.
Although specific recommendations for total daily protein intake need to be tailored to the individual, it would be prudent for the populations outlined above to also consider protein distribution on a per meal basis.
Per meal protein distribution has received an increasing amount of interest in nutritional research due to the potential influence on health-related outcomes such as body composition, muscle mass and functional capacity.
Practical considerations include evenly spread, good quality protein feedings to promote an optimal per meal muscle protein synthesis stimulus. A per meal intake of 25-40g good quality protein should cover the majority of populations. The elderly, or larger individuals or those performing whole-body resistance training can aim towards the upper end of that range to maximise muscle protein synthesis.
Alternatively, protein recommendations within a mixed meal at an intake of 0.4-0.5g/kg of good quality protein per eating occasion appear to have beneficial effects. This accounts for inter-individual variation and is a suitable strategy for the populations described, particularly athletes, and for those looking to maximise muscle mass, and for the elderly. For an 80kg athlete, this is calculated at 32-40g of protein per meal.
To help meet the suggested per meal protein intakes outlined, click here for a list of high quality protein options and snacks.
To recap on the benefits of eating adequate protein, or at least 50% greater than the RDA:
- Increased recovery from training
- Increased adaptations to training
- Elevated muscle protein synthesis to build muscle and increase muscular strength
- Enhanced mitochondrial capacity to help ‘get fitter’
- Increased satiety from within a meal
- Maintenance of lean body mass during a calorie deficit (dieting)
- Growth and bone health
- Beneficial tool for weight loss and weight loss maintenance
If you have any questions or would like to contribute further insight into the topics described above, please feel free to leave a comment below.
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