Is there such a thing as an ideal protein source?
This article will address that question.
Differences in protein 'quality' between food-types (including protein supplements) will be explored and the data will act as a guide to help you to make an informed decision when it comes to food choice and supplements as a source of protein.
With all the marketing coming from the multi-billion dollar supplement industry and a lot of unfounded advice given by self-proclaimed 'health' gurus, simply put; are you wasting your money and time believing and following ill-advice?
Just so everyone is on the same page here, benefits of a higher protein diet when training include:
1) Increased lean body mass (Campbell, et al., 2018)
2) Increased satiety (Weigle, et al., 2005) (Helms, et al., 2015)
3) Increased retention of lean body mass when in a caloric deficit (Mettler, et al., 2010)
4) Decreased fat mass (Campbell, et al., 2018)
5) Increased rate of protein synthesis (recover, grow, adapt faster) (Hulmi, et al., 2010)
Conversely, the opposite is shown to occur following a low protein diet (Pezeshki et al., 2016).
This article will act as a guide to help you to make an informed decision when it comes to food choice and supplements.
To put it out there, other nutrients play a crucial role in health and performance too of course; this article will focus on the role of protein.
Let's talk about protein!
Protein - The Basics
Protein is required to be consumed from the diet, sources of which include meat, fish, dairy, mycoprotein, cereals, seafood, soy, legumes and eggs.
When digested, the hydrolysed protein yields base molecules - amino acids - which are an essential nutrient to support life.
These amino acids form the building blocks that allow for key functions including:
1) Synthesis of muscle, enzymes, antibodies, neurotransmitters, hormones.
2) Transportation of nutrients, fluids and electrolytes.
3) Growth and repair of cells including muscle.
4) As an energy source.
Every cell in the body relies on a supply of amino acids to function, grow and repair.
'Quality' Protein and Amino Acids
The term 'quality' protein is commonly used to describe protein which contains all of the Essential Amino Acids.
Amino acids can be categorised as being either:
1) Essential - not synthesised in the body and must come from the diet.
2) Conditionally essential - required during particular health or developmental circumstances.
3) Non Essential - synthesised in the body in sufficient quantities for health
Amino Acid Profile Comparison
In this section we will directly compare the protein 'quality' between foods by comparing the amino acid composition of each food type.
The values have therefore been adjusted to reflect the mg quantity of each amino acid per gram of protein, not the weight of the food.
Table 2. Comparison of Amino Acid Composition Between Protein Sources
Source: https://ndb.nal.usda.gov/ndb/search/ Items searched: 15123, 01124, 13821, 14066, 20008, 20035, 16122 [accessed 10/03/2018]
For each amino acid, the highest and lowest value has been highlighted to demonstrate the maximum variation.
No food is entirely deficient or absurdly low in any amino acid.
As evident in Table 2, no single food type is outright deficient or contains the highest proportions across all amino acids.
Egg white contains the highest number of essential and conditionally essential amino acids. However it scores the lowest for tryptophan and proline.
Whey protein scores the highest for amino acids which egg white scores the lowest - tryptophan and proline.
Overall, all sources contain comparable quantities of all amino acids, with the biggest difference seen for cysteine, between tuna 9.1mg/g and egg white 27.3mg/g is 3-fold.
Provided you can consume larger quantities of each food type in isolation, the slight differences become non-significant.
However the practicality of using each food as a singular source of protein is less straightforward.
Table 3. Comparison of Macro-nutrients Between Foods
Source: https://ndb.nal.usda.gov/ndb/search/ Items searched: 15123, 01124, 13821, 14066, 20008, 20035, 45077339 [accessed 10/03/2018]
As evident from Table 3, the proportions of macro-nutrients varies significantly between food types.
This has significant ramifications with regards to the practicality or usefulness of each food type as the singular source of protein, dependant on the desired daily fat and carbohydrate intake.
Due to the proportions of carbohydrates and fat obtaining the recommended protein intake for training of 1.2 - 1.7g protein per kg per day would yield the following macro-nutrient intakes for each food for a 70kg individual:
Table 4. Macro-nutrient Ranges for Adequate Daily Protein Intake
As shown in Table 4, grain-sources of protein contain a huge amount of calories due to the high quantity of fat and carbohydrates present.
Discussion: Practical Considerations..
Despite all analysed foods containing comparable amino acid profiles not lacking in any essential amino acids, animal sources of protein are more protein-dense per weight unit of food, i.e. per 100g
Grain-sources have macro nutrient ratios which render them very calorific, due to high proportions of fat and carbohydrates.
Obtaining a comparable amount of essential amino acids from grain/plant as from animal sources may become limiting by sheer portion volume, carbohydrate and fat content.
Grains and plant sources of protein are most useful if an increased quantity of carbohydrates and fat is desired.
It would at first seem like bad news for the vegetarians/vegans out there trying to retain lean body mass whilst losing fat, however the macro-nutrient ratio issue can easily be circumvented through supplementation of protein concentrates coming from these plant sources.
i.e. Soy protein isolates or pea protein isolates etc..
Omnivores have been doing this with whey protein for decades, the only difference being is that due to the slight differences in essential amino acid content, more plant protein should be consumed.
1) No food is entirely deficient or absurdly low in any amino acid to as to render it 'incomplete' or unworthy to be used as a protein source.
2) Variation on macro-nutrient ratios and food volume is the determining factor that results in particular foods making a more efficient protein source.
3) Protein supplementation with concentrated powders circumvents the problems that arise due to macronutrient ratios and food volume.
Stay tuned for the next article!
Campbell, BI., Aguilar, D., Conlin, L., Vargas, A., Schoenfeld, B.J., Corson, A., Gai, C., Best, S., Galvan, E., and Couvillion, K. (2010). Effects of High vs. Low Protein Intake on Body Composition and Maximal Strength in Aspiring Female Physique Athletes Engaging in an 8-Week Resistance Training Program. Med Sci Sports Exerc. 42(2):326-37.
Helms, E.R., Zinn, C., Rowlands, D.S., Naidoo, R., and Cronin, J. (2015). High-protein, low-fat, short-term diet results in less stress and fatigue than moderate-protein moderate-fat diet during weight loss in male weightlifters: a pilot study. Am. J. Clin. Nutr. 82(1):41-8.
Hulmi, J.J., Lockwood, C.M., and Stout, J.R. (2010). Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutr. Metab. (Lond). 7: 51.
Mettler, S., Mitchell, N., and Tipton, K.D. (2015). Increased protein intake reduces lean body mass loss during weight loss in athletes. Int. J. Sport Nutr. Exerc. Metab. 25(2):163-70.
Pezeshki, A., Zapata, R.C., Singh, A., Yee, N.J., and Chelikani, P.K. (2016). Low protein diets produce divergent effects on energy balance. Sci. Rep. 6:25145.
Weigle, D.S., Breen, P.A., Matthys, C.C., Callahan, H.S., Meeuws, K.E., Burden, V.R., and Purnell, J.Q. (2005). A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations.
Database searches for food nutrients: https://ndb.nal.usda.gov/ndb/search/ Items searched: 15123, 01124, 13821, 14066, 20008, 20035, 16122, 45077339 [accessed 10/03/2018]