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What are proteins?

After water our body is mostly composed of proteins. Indeed, proteins are the main component of cells and are essential to life. Proteins are often called “the building blocks of life”.

Proteins have complex structures: 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 proteins
  • Hemoglobin which transports oxygen around the body
  • Most hormones which act as your body’s chemical messengers are also proteins
  • 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

Did you know?

A study showed that up to half of elderly people consume less than the daily recommended amount of protein. Inadequate protein intake is closely linked to loss of muscle strength and functionality.

Hartz, S. C. (1992) The WSS study population. In: Nutrition in the Elderly: The Boston Nutritional Status Survey (Hartz, S. C., Russell, R. M. & Rosenberg, J. H., eds.), London, Smith-Gordon, pp. 17–25.

Did you know?

The European Society of Clinical Nutrition and Metabolism (ESPEN) expert group have recommended increasing protein intake in elderly people compared to younger adults.

Deutz NE, et al. Protein intake and exercise for optimal muscle function with ageing: Recommendations from the ESPEN Expert Group. Clin Nutr. 2014.
water drinking

Did you know?

The European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) has issued a consensus statement by which post menopausal women are recommended a higher protein intake (1.0-1.2g/kg/day) than the rest of healthy adults

Rizzoli, R. et al. The role of dietary protein and vitamin D in maintaining musculoskeletal health in postmenopausal women: A consensus statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO). Maturitas (2014).

Did you know?

Higher protein intake is associated with better strength, physical performance, and lean muscle mass in older adults.
Did you know?
Protein is part of every cell. tissue & organ in our bodies. It contributes to building, repairing & maintaining tissues. Skin, nails, hair, muscles & bones are all made up of protein.
Did you know?
Many hormones & enzymes that regulate body processes & chemical reactions are made of protein.
Antibodies, which form part of our immune response to fight disease, are also made of proteins.
Did you know?
Proteins consist of amino acids. There are 20 amino acids needed by the body - 9 of which are "essential" and are not produced by the body.
Did you know?
Protein from animal sources (e.g. meat, fish and dairy products) contain the full range of essential amino acids. Grains, fruits, vegetables and nuts are sources of protein but may lack one or more essential amino acids.
Did you know?
Protein likes company!
Consuming the right amount of protein is important.
Magnesium and Zinc contribute to normal protein synthesis
Folate is also important for normal amino acid synthesis
Not all protein is created equal

Dietary sources of protein include meats, eggs, plants and dairy products and not all of those are created equal. To assess the quality of dietary protein three criteria can be considered: protein biological value, protein efficiency ratio, and net protein utilization.

1. Biological value: based on the quantity of essential to non-essential amino acids. (Amino acids are the chemical units that constitute protein. While the human body can manufacture most amino acids on its own, it cannot synthesize certain amino acids in sufficient amounts to meet the body’s needs. Such amino acids are called “essential amino acids” because it is crucial that the body acquires them through dietary sources)
2. Protein efficiency ratio: indicating ability of a protein to support growth
3. Net protein utilization: percentage of amino acids converted to tissue protein versus the amino acids digested

Below are examples of different types of protein and their respective quality.

Quality Comparison between Protein Sources7

Type of Protein

Biological Value

Protein Efficiency Ratio

Net Protein Utilization

Whey (dairy)




Milk protein (~80% Caseinate and ~20% whey protein)




Casein (dairy)




Soy Protein (plant)




Additional sources support health benefits of protein for the elderly

People with low protein intake have higher bone and lean muscle mass loss:

  • The scientific community and health authorities such as the European Food Safety Authority (EFSA) agree that protein from diet has a beneficial effect on the whole lean body mass, including muscle mass6.
  • The European Food Safety authority also states that protein is essential for the growth and maintenance of bones. Bone mass is at its maximum between ages 25 and 35 years and after this, there is a gradual decrease, which becomes more prominent with time11.

Older adults should seek to get enough protein through a healthy and balanced diet, and/or with the support of high quality nutritional supplements.

To learn more, read about Maintaining Mobility and The Allies for Healthy Aging.