The main dietary sources of protein come from: -
Animal Sources: Meat, poultry, fish, eggs and dairy products
Plant Sources: Grains, legumes, vegetables
Generally-speaking, animal sources are viewed as ‘high-quality’ or ‘complete’ sources of protein as they contain all the essential amino acids needed by humans. Most plant sources of protein are known as ‘low quality’ or ‘incomplete’ proteins as they lack one or more of the essential amino acids. This is why vegetarian and vegan diets need to be carefully planned to ensure that all essential amino acids are derived from the diet. For example, legumes are often consumed with grains as their amino acid combinations are complementary.
How Much Protein Do I Need?
Recommended Intakes for strength training individuals is 1.6-1.8g per kg of bodyweight. Therefore for an 80kg person this relates to a daily intake of between 128g-144g of protein per day. There is no research to suggest more muscle can be built with intakes higher than 1.8g/kg. For example, Hoffman et al (2006) found no support for protein intakes greater than 1.6-1.8g/kg in collegiate strength & power athletes for altering body composition.
Instances where it can be argued that a slightly higher intake may be optimal is in the case of beginner trainees embarking on strength training. In this scenario you could bring intakes up to 2.0g/kg of bodyweight. This is because beginners can expect to build large amounts of muscle mass when embarking on a strength training program.
Vegetarians will generally need an intake of 2.4g/kg of protein per day. This is due to the lower quality of pant-based protein which means less of the protein is absorbed by the body.
For the average gym goer who isn't looking to maximise muscle mass and just wants to lose a little weight, intakes of 1.2g/kg-1.4g/kg will be more than sufficient in maintain lean mass whilst losing body fat.
Benefits of Higher Protein Intakes: -
- Enhanced Muscle Building: An insufficient protein intake will impair someone’s ability to build muscle. This is bad news whether your goals are to build muscle or lose fat because having more lean muscle mass is important to both processes.
- Higher Thermic Effect of Food (TEF): The thermic effect of food relates to the amount of energy required to digest and absorb food. Of the 3 macronutrients, protein has the highest TEF. In practical terms this means that your body will expend more energy digesting and absorbing a high protein diet than a low protein diet, aiding in fat loss.
- Satiety: Protein is also the most satiating of the 3 macronutrients. This is excellent news for anyone wanting to lose fat, as having a high protein diet will keep them feeling fuller for longer, reducing the chance of snacking and over-eating.
- Reduced Chance of Sarcopenia: Sarcopenia is the involuntary loss of muscle mass with age, and affects up to 25% of older adults (Gregorio, et al, 2014). Women in this study who protein intakes below 1.1g/kg had higher body fat and fat-to-lean ratios than those who consumed a higher protein intake. Higher protein intakes can offset the loss of muscle mass with ageing, which is vital to health and well-being in the older populations.
Protein Distribution
Now we know how much protein we should be consuming, it is important to consider how the protein should be distributed across the day. Traditional dietary patterns generally has protein intakes skewed towards the end of the day, with a small intake at breakfast (which is usually more carb-heavy), a moderate amount at lunch, and a larger, bolus dose of protein with the evening meal. However, for the stimulation of muscle growth, a more even distribution across all meals is more effective (Mamerow, et al, 2014). This is because the body has a limited capacity to store excess protein from a single meal and acutely stimulate muscle growth at a later time, it is better to take more of an even distribution across meals throughout the day. For example, a 90g serving of protein has no greater effect on muscle protein synthesis than a more modest 30g serving.
Leucine Threshold
Leucine is one of the 9 essential amino acids, and is particularly important for us to consider as it stimulates mTor, which is highly important for muscle growth (Norton & Layman, 2006). To optimise muscle growth the total daily intake of protein is vital, but so too is the optimal intake of leucine. It is fairly easy to ensure you consume enough leucine if you follow the recommended intakes in this article and you consume a complete source protein with each meal. To ensure you meet your leucine requirements, you should consume 3g/kg of protein from a complete source in each meal. So for an 80kg individual this equates to 24g per meal. Reaching the leucine threshold in every meal is another reason why a more even distribution of protein is better than a skewed distribution, as the meals with only small amounts of protein may not reach the leucine threshold and as a result won’t stimulate muscle protein synthesis.
In Summary: -
- Protein intake may vary slightly, but generally speaking, for most strength trainees, an intake of 1.6-1.8g/kg is the recommended daily intake
- Higher protein diets are beneficial for increasing muscle mass, increasing the TEF and Increasing satiety
- Protein intakes should be evenly distributed across all meals of the day
