There are many different types, shapes and sizes of protein powder. They can be a useful supplement to a balanced diet by providing lean protein with a full spectrum of amino acids. But there can sometimes be some confusion as to why proteins are useful, what to look for in a protein supplement and who would benefit from a protein supplement. This blog reviews the functions of protein and why, how and when protein supplements are recommended.
Functions of protein
Structure – Protein is a building block of our body tissue and is a structural component of every cell in our body, therefore it is important for growth and repair. It makes up half the body’s dry weight and is the second most abundant compound after water. It is a primary component of muscle, hair, skin, nails, eyes as well as internal organs. Organs such as the heart and gut are made up of muscle fibers as well a skeletal muscle, hence muscle is essential for health as well as overall fitness and strength. Collagen is also a protein which makes up extracellular matrices, essential for bone, joints and cartilage.1
Repair and growth – as proteins are fundamental structural and functional elements within every cell of the body, they are essential for growth and repair. Protein deficiency is associated with stunted growth in children especially from low income families and developing countries. We require a constant supply of amino acids to build proteins that create our body tissues. This is true from pregnancy as well as growing children. However, we are constantly repairing, breaking down and regenerating body tissues. During times of healing, illness, following surgery, injuries and burns, a higher amount of protein production is required. Therefore, protein deficiency can increase healing times or prevent adequate healing and repair.2
Hormones/neurotransmitters/enzymes – amino acids (building blocks of protein) and proteins are precursors to hormones, enzymes and neurotransmitters eg: 2
- Tryptophan – converted to 5HTP which is then converted to serotonin and then melatonin when exposed to darkness, thereby supporting mood and sleep 3
- Tyrosine – is important to produce thyroid hormone (thyroid hormone is made up of tyrosine and iodine), also the neurotransmitter dopamine which is essential for mood, motivation and movement, dopamine is then converted to noradrenaline
- Insulin – is made from a protein composed of 2 chains
- Enzymes – essential for normal bodily processes including digestion are complex proteins
- Haemoglobin, antibodies and other transport proteins – produced from amino acids
Liver conjugation– amino acids are required for phase 2 liver conjugation. Adequate amounts of protein with special attention to glycine, l-glutamine, methionine, l-cysteine and N-acetyl-cysteine along with inorganic selenium and addition of taurine very important in the support of phase 2 activity. 1
Satiety – protein is broken down into energy more slowly than carbohydrate and has been shown to delay stomach emptying, making people feel fuller for longer. As it is broken down more slowly it can reduce the insulin response even when combined with carbohydrates, therefore it can support insulin sensitivity and therefore reduce sugar and carbohydrate cravings. Protein also triggers satiety neuropeptides including GLP-1, increasing feelings of satiety and fullness. Therefore, including protein in every meal is associated with reduced carbohydrate carvings as well and caloric intake in some circumstances, as well as a reduce insulin response which can encourage fat loss.4–7
Energy – although the body will always favour carbohydrate over protein for energy production, protein can be used as an energy source. Protein is converted to glucose for energy via gluconeogenesis. This process is less efficient than direct carbohydrate metabolism and therefore there is less net gain of ATP (or energy). However, when carbohydrate intake is reduced, protein will be used as an energy source. Also, when energy intake in less than energy output, protein from muscle and other body tissues can be broken down in order to produce energy.2
Other– proteins are also important for regulating osmotic pressure via fluid and salt balance as well as maintaining an acid-alkali balance by acting as a buffer.
There are a few groups of people who may be susceptible to protein deficiency, or inadequate protein intake.
Vegan– although vegans can certainly get adequate protein from their diet, it is not as easy as with an animal product diet. Although vegan sources of protein are readily available most do not contain the full spectrum of the 20 amino acids that are required and utilised by the body. Therefore, it is important that vegans alternate their sources of protein in order to obtain the full spectrum of amino acids. A vegan protein powder is a good way of ensuring intake of all 20 amino acids.
Reduced digestive function – stomach acid is essential for starting the process of protein digestion as well as the activation of proteolytic enzymes (enzymes which breakdown protein). Pancreatic and absorptive function are also necessary for absorption of amino acids. Therefore, if digestive function is impaired there may be an issue with absorption of protein. The protein status of individuals with conditions such as hypochloridria, inflammatory bowel disease and coeliac disease should be considered and a protein supplement may be useful in these cases.
As we age our digestive capacity reduces, as well as appetite and dietary intake. One symptom of aging is loss of muscle or sarcopenia which is thought to contribute to many aspects of reduced health as we age. Therefore, ensuring adequate protein intake and absorption in the elderly is essential.1
Athletes – high amounts of intensive exercise can often lead to a caloric deficit. Many athletes are looking to maintain or reduce weight without loss of lean mass (or muscle), therefore it is essential to ensure adequate protein intake in these individuals.
Athletes/Sports Nutrition– protein is important in sports performance as it can boost glycogen storage, reduce muscle soreness and promote muscle repair. For those who are active regularly, there may be benefit from consuming a portion of protein at each mealtime and spreading protein intake out throughout the day. It also may be advantageous in preventing lean mass losses during periods of energy restriction to promote fat loss. For some athletes it does appear, however, that there is a good rationale for recommending to athletes protein intakes that are higher than the RDA. Our consensus opinion is that leucine, and possibly the other branched-chain amino acids (isoleucine and valine), occupy a position of prominence in stimulating muscle protein synthesis.5,8,9
Weight loss – Weight loss studies have shown that using a protein powder as a meal replacement supports weight loss whilst still preserving lean body mass, therefore it is thought to support fat burning. Additionally, it can help support a reduced calorie diet by meal replacing with a lower calorie option as well as supporting satiety, therefore contributing to a reduced energy intake.
Increasing dietary protein intake to values higher than commonly recommended has a beneficial effect on retention of lean mass during hypoenergetic periods of weight loss. Meta-analyses of trials have shown that higher protein, at the expense of carbohydrate, improves the amount of fat loss and preserves lean tissue.8,9
Sarcopenia – Sarcopenia is a loss of muscle mass and function in the elderly that reduces mobility, diminishes quality of life, and can lead to fall-related injuries, which require costly hospitalisation and extended rehabilitation. However, ageing does not inevitably reduce the anabolic response to a high-quality protein meal. Ingestion of approximately 25–30g of protein per meal maximally stimulates muscle protein synthesis in both young and older individuals. However, muscle protein synthesis is blunted in elderly when protein and carbohydrate are co-ingested or when the quantity of protein is less than approximately 20g per meal. Supplementing regular mixed-nutrient meals with leucine may also enhance the muscle protein synthetic response in elders.10
With sarcopenia it is also important to consider optimal intake of all nutrients which are essential for the maintenance of muscle tissue. Vitamin D in particular is important as it is intrinsically involved in retention of muscle mass which aids with proprioception. Therefore it is a good idea to consider a powder which is designed as a meal replacement which has a multivitamin and mineral included, or consider a multivitamin and mineral in addition.10
If a protein powder is used as a meal replacement it is a good idea to include one which also acts as a multivitamin and mineral to ensure optimum intake of nutrients. Some will additionally contain superfoods, phytonutrients and live bacteria, which can contribute to overall wellness while supporting nutrient intake and digestive flora.
The source of protein can also be important. Whey protein is the most common in commercial protein powders and has been used the most in research papers. However, it comes from a dairy source so is therefore unsuitable for those with dairy allergies, lactose intolerance or vegans. As whey contains lactose whey protein will additionally have significant amounts of carbohydrate. Some people have problems digesting whey protein and experience symptoms such as bloating, gas, stomach cramps and diarrhoea.
Dairy free protein sources often come from soy, this will be more suitable for those who cannot include dairy but it can be more difficult to digest and most sources of soy are inorganic and contain GMOs, as well as phytates which are anti-nutrients (reduce absorption of other nutrients). This has been associated with poor health and can be very high in phyto-oestrogens such as isoflavones, which may disrupt normal hormone signaling if taken in excess.
Hemp, pea, chickpea and sunflower proteins are vegan sources and have the benefit of not coming from soy. It is important if looking for a vegan protein that there is a combination of sources to include all 20 amino acids. These sources tend to be well digestated and tolerated and do not contain dairy.
While no major studies link high protein intake to kidney damage in healthy individuals, excess protein can cause damage in people with pre-existing kidney disease.
This is because of the excess nitrogen found in the amino acids that make up proteins. Damaged kidneys have to work harder to get rid of the extra nitrogen and waste products of protein metabolism.
- Protein is essential for normal structure, function, growth, repair and maintenance if the human body. It can also be used as a source of energy. It is mainly found in skeletal muscle, hair, skin, nails, internal organs and connective tissue
- Protein increased satiety and can help stabilise blood sugar levels therefore supporting insulin sensitivity and preventing sugar cravings
- Protein and amino acids are essential for the production of hormones, neurotransmitters and enzymes
- Protein deficiency can increase the likelihood of sarcopenia or muscle loss.
- Vegans, those with digestive insufficiencies as well as those training intensively may struggle to obtain adequate levels of protein
- Protein powders can be a useful supplement to those prone to inadequate protein intake as well as those looking to reduce weight or prevent muscle loss
- Vegan protein needs to contain a mix of different plant proteins to ensure it contains all 20 amino acids but is well tolerated and suitable for those avoiding dairy or whey and soy protein
If you have questions regarding the topics that have been raised, or any other health matters, please do contact me (Helen) by phone or email at any time.
Amanda Williams and the Cytoplan Editorial Team
- Bland J et al. Textbook of Functional Medicine.; 2008.
- Haas EM. Staying Healthy with Nutrition.; 2006.
- Parker G, Brotchie H. Mood effects of the amino acids tryptophan and tyrosine. Acta Psychiatr Scand. 2011;124(6):417-426. doi:10.1111/j.1600-0447.2011.01706.x
- Halawi H, Camilleri M, Acosta A, et al. Relationship of gastric emptying or accommodation with satiation, satiety, and postprandial symptoms in health. Am J Physiol – Gastrointest Liver Physiol. 2017;313(5):G442-G447. doi:10.1152/ajpgi.00190.2017
- Effects of a Protein Preload on Gastric Emptying, Glycemia, and Gut Hormones After a Carbohydrate Meal in Diet-Controlled Type 2 Diabetes. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2732158/. Accessed July 9, 2020.
- Ma J, Stevens JE, Cukier K, et al. Effects of a protein preload on gastric emptying, glycemia, and gut hormones after a carbohydrate meal in diet-controlled type 2 diabetes. Diabetes Care. 2009;32(9):1600-1602. doi:10.2337/dc09-0723
- Ahima RS, Antwi DA. Brain Regulation of Appetite and Satiety. Endocrinol Metab Clin North Am. 2008;37(4):811-823. doi:10.1016/j.ecl.2008.08.005
- Guo X, Xu Y, He H, et al. Effects of a Meal Replacement on Body Composition and Metabolic Parameters among Subjects with Overweight or Obesity. J Obes. 2018;2018. doi:10.1155/2018/2837367
- Naclerio F, Larumbe-Zabala E. Effects of Whey Protein Alone or as Part of a Multi-ingredient Formulation on Strength, Fat-Free Mass, or Lean Body Mass in Resistance-Trained Individuals: A Meta-analysis. Sport Med. 2016;46(1):125-137. doi:10.1007/s40279-015-0403-y
- Paddon-Jones D, Rasmussen BB. Dietary protein recommendations and the prevention of sarcopenia. Curr Opin Clin Nutr Metab Care. 2009;12(1):86-90. doi:10.1097/MCO.0b013e32831cef8b