PROTEIN ‘What, When and Which to choose?’

By: Laura Viner, Nutrition & Wellness Coach at One5 Health

When it comes to protein there are no absolutes, it’s a question of considering what you need based on age, activity and quality. There's an abundance of research into protein needs, especially around ageing and muscle mass. Much of it is conflicting, so taking a personalised approach and exploring the nuances of the research is essential in understanding how it applies to you. 

Protein is an essential macronutrient, meaning we need to consume it for a wide range of bodily functions. These include muscle growth and repair, and forming antibodies for our immune system. Proteins also act as enzymes, neurotransmitters and hormones. Protein is made from chemicals called amino acids, which are strung together in chains. There are 20 amino acids in total, and 9 of these are known as 'essential amino acids". This means they can't be made by the body and need to be included in our diet. 

The UK Reference Nutrient Intake (RNI) is 0.75 gram/kg of body weight. This is the minimum requirement needed for a healthy, average weight, sedentary person aged 20-40. For the average adult female that’s 45g grams per day, and for males it’s 55.5 grams per day. This is equivalent to two portions of meat, fish, nuts or tofu;  about the size of the palm of your hand. 

Our needs vary, depending on age, weight, gender, activity level, and other bodily states, such as pregnancy, old age, or if you’re recovering from surgery or injury. For over 65’s studies show that 1.2g/kg body weight is optimal and in patients with sarcopenia (loss of muscle mass)  this rises to 1.2-1.4g/kg body weight.

As we age, our ability to make new muscle remains the same but amino acids are less efficiently assimilated into new muscle tissue, which means we have a higher protein requirement. Muscle loss in later life is implicated in a lower life expectancy, highlighting the importance of an adequate protein intake alongside exercise as we age.

 A safe upper limit of protein intake is no more than double the RNI, so in the UK that’s 1.5g/kg body weight per day: https://bmicheck.co.uk/protein-intake-calculator/ 

Quick tips for including protein in your diet: 

• Choose high quality protein sources, from unprocessed foods such as animal or plant proteins rather than protein supplements. 
• Spread your protein intake equally across meals i.e. 15g at breakfast, lunch and dinner. Avoid consuming your total protein needs in your evening meal. This will maximise the benefits of your protein intake, whilst reducing  any negative consequences such as kidney problems or weight gain, especially if you are exceeding the RNI. 
• If you are restricting calories or skipping meals it’s essential that you reach your daily protein requirement. This will ensure you maintain muscle during weight loss and  prevent sarcopenia, the loss of muscle mass, and strength associated with ageing. 
• If you are over 65, ensure you are both eating enough protein and doing regular resistance training to maintain and/ or build muscle. 

Research into the effects of dietary protein intake is ongoing. Here are some interesting areas of research currently being explored. 

WEIGHT MANAGEMENT 

Studies have shown that higher protein diets can increase satiety due to regulation of the hormone leptin which regulates appetite. This in turn results in healthier food choices, a reduction in overall calorie intake across the day.

Studies found that including 30g protein at breakfast had the most significant impact on daily calorie intake compared to a meal with 30g protein later in the day. 

 In weight loss studies the groups given higher protein diets, generally feel more full, and lose more fat, despite both groups experiencing similar weight loss. This is an important consideration for older adults (40+) who need to maintain muscle during weight loss. 

MUSCLE SYNTHESIS 

Leucine is the amino acid most associated with muscle growth so favouring foods high in leucine (eggs, fish, meat, soy, nuts, legumes) is a consideration. Studies suggest that muscle growth is triggered by consuming over 20g of protein, across a minimum of 2 meals per day. Most studies report that an increase in muscle mass is only achieved through increased protein intake of up to 1.2-1.6g/ kg bodyweight per day plus resistance activity and stretching. Younger subjects experience the greatest effects on muscle mass, in part due to the decreased efficiency of amino acid assimilation to muscle as we age. 

The timing of protein intake seems less important for regular exercisers, than those starting out. Sports studies found that replenishing protein after exercise in people who were new to exercise was beneficial, but there was no benefit in those who had been exercising regularly for 2 years or more. 

ANIMAL AND PLANT PROTEINS 

The idea that plant proteins are inferior to animal proteins hinges on the fact that foods like meat, eggs and dairy naturally contain all nine of the essential amino acids, but plant proteins such as mycoprotein, beans and tofu lack some of these essential amino acids. Studies have demonstrated that combining plant proteins with grains or nuts across a day, does provide all nine essential amino acids, but there is debate about how efficiently different protein sources are used by the body. Plant sources may be only 60-70% available (due to being attached to fibre), compared to 90-95% for animal products, so a vegan may need to increase the 0.75g RNI, to 1.1-1.2g protein/kg bodyweight. 

It’s worth considering that animal proteins contain saturated fats, which are associated with high cholesterol and cardiovascular disease  and that red and processed meats are associated with a higher risk of some cancers. On the other hand, plant proteins contain fibre and unsaturated fats which improve cholesterol levels, gut health and insulin sensitivity. While adults aged 18-45 may be able to meet their protein needs with only plant proteins, research suggests that over 65’s may benefit from animal protein due to less efficient assimilation to muscle. Increasing protein variety in the diet has benefits for everyone, and is a key consideration for vegans and vegetarians in reaching essential amino acid requirements.

HIGH PROTEIN DIETS 

A high protein diet supplies 35% or more of daily total energy as protein. Energy balanced high protein diets of under 3 months show reductions in insulin resistance and enhanced glucose metabolism in overweight subjects, however long‐term high protein diets of over 6 months seem to have the opposite effect, increasing insulin resistance, and glucose intolerance in healthy subjects. Furthermore, several long‐term observational studies have found an association between high protein intake and impaired renal function. This indicates that a high protein diet could be a useful intervention in the short term, but could actually be harmful if followed for longer periods. 

PROTEIN VALUES 

Food is packaged up with different nutrients so try to consider this when choosing which proteins you eat.  Processed proteins such as fake meats, energy bars, and dairy alternatives might include other non- nutrient ingredients such as emulsifiers, colours, and artificial sweeteners. 

Use this list to help plan your protein intake: 

• 30g Mixed nuts- 6.7g protein
• 30g parmesan cheese- 10.7g protein
• 30g Pumpkin seeds- 7.3g protein
• 30g Edamame beans- 4g protein
• 2 boiled eggs- 11g protein
• 80g Tinned sardines in oil- 19.7g protein
• S80g Sirloin steak- 24.5g protein
• 80g Chickpeas- 5.6g protein
• 80g chicken- 21.9g protein
• 80g salmon- 17g protein
• 80g silken tofu- 9.6g protein

References 

• Darling AL, Manders RJF, Sahni S, Zhu K, Hewitt CE, Prince RL, Millward DJ, Lanham-New SA. Dietary protein and bone health across the life-course: an updated systematic review and meta-analysis over 40 years. Osteoporos Int. 2019 Apr;30(4):741-761. doi: 10.1007/s00198-019-04933-8. Epub 2019 Mar 21. PMID: 30903209. 
• Kamyar Kalantar-Zadeh, Holly M Kramer, Denis Fouque, High-protein diet is bad for kidney health: unleashing the taboo, Nephrology Dialysis Transplantation, Volume 35, Issue 1, January 2020, Pages 1–4, https://doi.org/10.1093/ndt/gfz216
• Layman, D.K. Dietary Guidelines should reflect new understandings about adult protein needs. Nutr Metab (Lond) 6, 12 (2009). https://doi.org/10.1186/1743-7075-6-12 
• Lipina C, Hundal HS. Lipid modulation of skeletal muscle mass and function. J Cachexia Sarcopenia Muscle. 2017 Apr;8(2):190-201. doi: 10.1002/jcsm.12144. Epub 2016 Oct 8. PMID: 27897400; PMCID: PMC5377414. 
• Mertz KH, Reitelseder S, Bechshoeft R, Bulow J, Højfeldt G, Jensen M, Schacht SR, Lind MV, Rasmussen MA, Mikkelsen UR, Tetens I, Engelsen SB, Nielsen DS, Jespersen AP, Holm L. The effect of daily protein supplementation, with or without resistance training for 1 year, on muscle size, strength, and function in healthy older adults: A randomized controlled trial. Am J Clin Nutr. 2021 Apr 6;113(4):790-800. doi: 10.1093/ajcn/nqaa372. PMID: 33564844. 
• Morton RW, Murphy KT, McKellar SR, et alA systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adultsBritish Journal of Sports Medicine 2018;52:376-384. 
• Naghshi S, Sadeghi O, Willett W C, Esmaillzadeh A. Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies BMJ 2020; 370 :m2412 doi:10.1136/bmj.m2412 
• Nunes E. A., Colenso-Semple L., McKellar S. R., Yau T., Ali M. U., Fitzpatrick-Lewis D., Sherifali D., Gaudichon C., Tomé D., Atherton P. J., Robles M. C., Naranjo-Modad S., Braun M., Landi F., and Phillips S. M. (2022) Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults, Journal of Cachexia, Sarcopenia and Muscle, 13, 795–810, https://doi.org/10.1002/jcsm.12922 
• Yanagisawa Y. How dietary amino acids and high protein diets influence insulin secretion. Physiol Rep. 2023 Jan;11(2):e15577. doi: 10.14814/phy2.15577. PMID: 36695783; PMCID: PMC9875820. 
• Reddy, M. (2013) Hibernian hardboiled: race & gender in contemporary Irish crime fiction. [Podcast]. 24 November 2013. Available at: http://www.ucd.ie/humanities/events/podcasts/2013/irish-crime-fiction/index.html (Accessed 31 January 2014).
• Hill, S (2023) Plant Proof: The Science of Protein-Masterclass for Muscle Growth & Longevity [podcast] 4 December 2023. Available at https://www.youtube.com/watch?v=vGKETUDSrnc 
• Wolf, J (2023) Zoe: Everything You Know About Protein is Wrong - Christopher Gardner [podcast] 17 April 2023. Available at https://www.youtube.com/watch?v=DMwf_9wqWY0 
• Attia, P (2022) The Drive: Dietary protein - Don Layman [podcast] 26 September 2022. Available at https://www.youtube.com/watch?v=BqmG2y4IeY8 
• Lennon, D (2022) Sigma Nutrition: Plant or Animal Protein - Rethinking Protein & Muscle Eric Helms September 13, 2022. Available at https://sigmanutrition.com/episode454/ 
• Nutrition values from https://cronometer.com/ (2024) accessed 14 March 2023