HealthyRetired · Food

We often hear that we need protein to maintain muscle. But what is protein made of, and what does the body actually do with it? The answer begins with amino acids: small molecules that join together in different sequences to form proteins. [1]

You do not need to memorise their names before making breakfast. Understanding a few basics can help you choose meals more confidently and make sense of supplement claims.

From food to the body's own proteins

When we digest protein, our bodies break it down into smaller components, including amino acids. These become raw materials for making the proteins we need for tissue repair and many other functions. Amino acids can also provide energy. [1]

Protein has a much wider job than building biceps. Proteins maintain tissues and support immune function. They are continually made and broken down in a process called protein turnover. [2]

Think of food protein as a supply of building materials. Eating a particular protein does not mean it travels intact to whichever part of the body we hope to improve.

Essential does not mean the others are unimportant

For adults, nine amino acids are called essential because the body cannot make enough of them to meet its needs; they must come from the diet. Nonessential amino acids are ones the body can make. The name describes their dietary requirement, not their importance. [1]

Some are conditionally essential: under particular circumstances, such as illness or major physical stress, the body's own production may not meet demand. This is a reason for individual nutritional care when needed, rather than a reason for everyone to buy supplements. [1]

The nine essential amino acids

The nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. [1]

They work as part of a larger nutritional system. A food does not need to have an impressive-sounding amino acid on its label to be useful. Ordinary beans, tofu, eggs or milk already supply amino acids through their protein.

Leucine, isoleucine and valine are also known as branched-chain amino acids, or BCAAs. Leucine helps stimulate muscle protein synthesis, particularly in the context of exercise, but muscle building still requires the other essential amino acids. Three members of the team cannot do everybody else's work. [3]

Can plant foods supply them?

Yes. Animal foods are not the only option. Beans, lentils, chickpeas, soy foods, nuts, seeds and grains all contribute protein. Milk, yoghurt, eggs, fish and meat are other sources for people who eat them. [2]

A protein described as complete provides all nine essential amino acids in suitable proportions. Most plant proteins contain all nine too, but their proportions differ: an amino acid present in a relatively small amount can limit how efficiently that protein meets our needs. [2]

This does not make beans or grains inferior foods. Eat a varied diet with adequate total protein and energy. You do not have to combine complementary proteins in precisely the same meal; balance across the day matters. [4]

For example, a day might include oats and yoghurt at breakfast, lentil soup at lunch, and tofu with rice and vegetables at dinner. These are meal ideas, not a calculated prescription.

Why this matters as we get older

Maintaining strength and independence requires attention to both food and movement. Expert guidance commonly suggests around 1.0-1.2 grams of protein per kilogram of body weight daily for healthy older adults, with needs adjusted to the person. For someone weighing 70 kg, that is about 70-84 grams of protein per day. [5]

Those numbers describe protein, not grams of meat or tofu. A food's weight includes water, fat and other components, so use its protein label when estimating intake.

Illness, appetite and kidney function can change the advice. In particular, people with kidney disease should ask their healthcare professional about a suitable target rather than increasing protein independently. Nutrition should accompany activity, including suitable strength exercises; extra protein alone is not a substitute for using our muscles. [5]

Do we need amino acid supplements?

Most people who meet their protein needs through a varied diet do not need to count or supplement individual amino acids. [2] NIH guidance finds inconsistent evidence that BCAA supplements stimulate muscle protein synthesis beyond what adequate high-quality dietary protein can achieve. [3]

Someone who struggles to eat enough may benefit from a clinician's or dietitian's assessment. The useful question is what is missing from that person's intake, not which powder has the longest chemical name.

A practical approach

Begin with meals. Give each main meal a recognisable protein ingredient, vary your choices and make food enjoyable enough to eat regularly. If chewing, poor appetite or unexplained weight loss makes that difficult, seek help instead of trying to solve everything with a single supplement.

Amino acids explain why protein matters. They also remind us that nourishment is a team effort: enough food, a varied diet and regular movement working together.

Sources and further reading

[1] MedlinePlus. Amino acids: https://medlineplus.gov/ency/article/002222.htm

[2] British Nutrition Foundation. Protein: https://www.nutrition.org.uk/nutritional-information/protein/

[3] NIH Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance; BCAA section: https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/

[4] MedlinePlus. Protein in diet: https://medlineplus.gov/ency/article/002467.htm

[5] PROT-AGE Study Group. Evidence-based recommendations for optimal dietary protein intake in older people, 2013: https://pubmed.ncbi.nlm.nih.gov/23867520/