Protein & Its Role in Healthy Ageing
What is protein?
After water, our body is mostly composed of protein. Indeed, protein is the main component of cells and are essential to life.
Protein has a complex structure: they are made up of many smaller units called amino acids. These are linked together in a chemical bond forming a long chain. Some of these amino acids are called ‘essential,’ meaning they are crucial for life but cannot be produced by the human body and must be gained through one’s diet.
There are many different types of proteins in the body. For example:
- Muscle mass is made of protein
- Collagen which provides strength and structure to tissues (e.g. cartilage)
- Skin, hair and nails which are mainly composed of protein
- Haemoglobin which transports oxygen around the body
- Most hormones which act as your body’s chemical messengers
- Enzymes which regulate all aspects of metabolism; they support important chemical reactions that allow you to digest food, generate energy to contract muscles, and regulate insulin production
- Antibodies which play a role in your immune response
The importance of protein for good health
Protein has many crucial functions. Did you know:
- The fibres of the muscle are made mostly of two proteins: myosin and actin. These slender fibres slide along one another to create movement. When dietary protein intake is too low, the mechanisms for movement can be affected.
- Proteins, like actin and tubulin, trigger essential processes in all living cells. These include cell division, cell shape maintenance and movements, amongst others.
Protein in the diet
Protein is a type of macronutrient (large, energy providing nutrient), which, along with carbohydrates and fats, is needed by the body to function normally. Our body is not able to store amino acids like it does carbohydrates and fats, so we need a daily intake to make new protein. Protein should be consumed evenly across the day and be part of each meal.
Protein can be found in:
- Animal sources, such as meat, fish, eggs and dairy products. These contain the full range of essential amino acids
- Nuts, grains, legumes and tofu, which may lack one or more essential amino acid
- Protein-containing nutritional supplements
Ageing adults’ challenge of getting enough protein
It is common for people to eat less food as they age. Contributing factors can be lack of appetite, changes to smell and taste, living alone, little interest in cooking, or difficulty in eating due to teeth/gum or denture problems. Eating less or eating sub-optimally means that older adults often miss out on getting enough important nutrients, despite their need for many nutrients being higher.
Protein is of particular concern. Although it was found that only 14% of older adults were not meeting the recommended intake for protein1, studies have shown that a higher intake of protein by older adults helps to reduce muscle loss with ageing2,3, and therefore helps to maintain muscle strength and function.
How much protein do older adults need on a daily basis?
The Recommended Dietary Intake (RDI) of protein for older Australians (>70 years) is 81g per day for males (or 1.07g/kg), and 57g per day for females (or 0.94g/kg)4. These requirements are greater than for adults under 70 years old, due to the need for additional protein to help to combat the loss in muscle mass associated with ageing.
There is evidence to suggest that requirements may be even higher than this, with some new international guidelines recommending 1-1.2g protein per kg per day for people over 65 years to help maintain and regain muscle mass and function5.
To help the body utilise this protein, it is recommended to spread out the intake over the day, rather than have it all at once. Research shows that consuming 25g of protein at each meal promotes optimal muscle synthesis6. Following are some examples of 25g of protein :
- A two-egg omelette with a handful of grated cheese
- A small tin of baked beans on toast with a tub of yoghurt
- A ham, cheese and salad sandwich
- 120g of meat, fish or chicken with vegetables
Older adults should seek to get enough protein through a healthy and balanced diet, and/or with the support of high quality nutritional supplements.
2 Scott D, Blizzard L, Fell J, Giles G, Jones G. Associations between dietary nutrient intake and muscle mass and strength in community-dwelling older adults: the Tasmanian Older Adult Cohort Study. J Am Geriatr Soc 2010; 58:2129-2134.
3 Houston DK, Nicklas BJ, Ding J, et al. Dietary protein intake is associated with lean mass change in older, community-dwelling adults: the Health, Aging, and Body Composition (Health ABC) Study. Am J Clin Nutr 2008; 87: 150-155.
4 NHMRC Nutrient Reference Values for Australia and New Zealand, 2005 https://www.nrv.gov.au/nutrients/protein (accessed November 2016)
5 Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE study group. J Am Med Dir Assoc 2013; 14: 542-559.
6 Paddon-Jones D, van Loon L. Nutritional approaches to treating sarcopenia.In: AJ Cruz-Jentoft, JE Morley, eds. Sarcopenia. Chichester, West Sussex: John Wiley & Sons, Wiley-Blackwell; 2012. p. 275-295.