What is protein?

Protein is one of the three nutrients, along with fat and carbohydrates, that we need in larger (macro) amounts in our diet. Our hair, skin, bone and muscle are all made from the protein we eat, as are the enzymes, hormones and neurotransmitters that play important messaging roles in the body.

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Protein is made up of long chains of smaller units called amino acids. These building blocks are used in the body for growth and repair. There are 20 amino acids in total, of which nine are essential – this means the body cannot make them, and they must be obtained from our diet.

Animal foods, like meat and fish, and certain plant sources – soy, quinoa, buckwheat and Quorn – contain all of the essential amino acids, making them high-quality protein sources. When we eat these foods, our digestive enzymes break them down to their smaller amino acid units, so they can be used by the body.

Discover our full range of health benefit guides including the 10 best sources of protein and our high-protein recipes. Make your own high-protein snacks, try our protein balls and turkey lettuce wraps.

Protein foods

Why is protein important?

As well as playing a key role in building and repairing cells, protein is also involved in keeping cells oxygenated and nourished. For example, our red blood cells contain a protein compound called haem that carries oxygen throughout the body. Similarly, a protein called albumin in the blood helps regulate water balance in our tissues, preventing swelling.

About half of the protein we eat is used to make enzymes; these help us digest our food, make new cells and build body chemicals. Protein is also important for immune function. It plays a key role in activating special immune cells called Natural Killer cells, and in the formation of antibodies that help fight off viruses and bacteria. Like fats and carbohydrates, protein is also a source of calories (4cal/gram) and can be used to fuel our activity.

What are the benefits of protein?

Ensuring you consume adequate amounts of protein may help:

  • Support recovery after exercise or injury
  • Reduce muscle loss
  • Curb appetite
  • Help with weight management
  • Regulate hormones, including during transformative stages, like puberty
  • Support additional growth and development needs, especially during pregnancy.

How might I know if my diet is low in protein?

If you’re not eating enough protein, you might first notice this in the worsening condition of your hair, nails and skin. Other signs might include wounds and injuries that take longer to heal; you might catch more colds and infections; suffer from anaemia and muscle weakness; and you may notice swelling of your legs, feet and hands. You may also experience fatigue and start to notice changes in your body composition, and even your posture.

What factors influence how much protein I need?

Our protein needs are unique to us and depend on factors like our age, weight, gender, general health and physical activity levels. As well as life stage; during pregnancy for example, the body needs more protein to satisfy the demands of additional tissue development and growth. Guidelines suggest an additional 6 grams of protein per day during pregnancy, increasing to 11 grams during the first six months of breast feeding.

Those who are physically active have increased needs, by exactly how much will depend on the type and intensity of their chosen exercise. That said, even those who have no or only low activity levels need to consume adequate protein in order to help counter the natural muscle loss we experience as we age.

It's during this later life, as we get older, that changes to how our body works, such as impaired digestion, insulin resistance and inflammation, alter how we access and make use of protein. This means we need to include more protein in our diet; not eating enough from high-quality sources may lead to an increased loss of muscle mass, known as sarcopenia, which may result in frailty and increase the chance of a fall.

'Protein' spelled out in blocks with foods surrounding it

How much protein do I need?

Protein should account for about 10-35% of your total daily calorie intake, this means for an average adult consuming 2000kcal per day, 200-700 of those calories should be derived from protein. In the UK the Reference Nutrient Intake (RNI) is 0.75 gram/kg of body weight. This is the minimum amount of protein needed and is based on an average, non-active adult. This guideline figure is often misrepresented as being a recommended optimal intake, but if you’re an adult looking to build muscle this is unlikely to be enough. That said, defining an optimal intake is tricky since our protein needs are specific to each and every one of us.

The best way to calculate your daily protein needs is using your weight. Based on averages from evidence-backed recommendations, a general rule of thumb is to eat about 1.2g protein per kg of body weight to maintain muscle. This may increase to 1.2-1.6g/kg of body weight when looking to add lean mass or if you’re a woman in midlife.

The following are minimum guidelines for different age groups – remember these are relevant for healthy, non-active individuals:

Young children (one to three years):

  • 14.5 grams per day

Pre-school children (four to six years):

  • 19.7 grams per day

School age children (seven to 10 years):

  • 28.3 grams per day

Adolescents (11-14 years)

  • Female: 41.2 grams per day
  • Male: 42.1 grams per day

Older teenagers (15-18 years)

  • Female: 45.4 grams per day
  • Male: 55.2 grams per day

Adults (19-50 years)

  • Female: 45g grams per day
  • Male: 55.5 grams per day

Older adults (50 years+)

  • Female: 46.5 grams per day
  • Male: 53.3 grams per day
Dairy foods

Does it matter what and when I eat protein?

Yes, it does – opting for high-quality protein is important – this refers to food sources that contain all the essential amino acids, including leucine, which is key for supporting muscle tissue. Eggs, yogurt and milk, as well as whey protein powder, soya milk and tempeh, are all useful sources of this important amino acid.

Including protein foods at each meal or snack throughout the day is thought to be more effective than having the majority of your protein intake in just one meal. In practical terms, this may involve two to three meals, each containing about 25-30g of high-quality protein. By including protein at breakfast, you’ll help curb your appetite and as a result, potentially support weight management.

People doing an intensive exercise programme may benefit from consuming protein after a workout, and similarly spacing their protein intake through the day.

Can I eat too much protein?

Consistently consuming more protein than your body needs may have a number of implications. For example, it may lead to elevated blood lipids and potentially heart disease, partly because many protein foods also contain fat and saturated fat. Our body doesn’t store excess protein so unless it can be used as energy it will be converted to fat for storage and the amino acids will be excreted from the body via the kidneys. Initially it was thought that high protein intakes placed additional strain on the kidneys, however, more recent findings suggest protein only poses a risk to kidney function for those with existing kidney disease or impaired function.

For the majority of healthy adults, long-term consumption of protein up to or at 2 grams/ kg of body weight per day is generally considered safe.

So, how much protein do I need?

How much protein you need is unique to you and depends on factors such as age, health status and how active you are, as well as whether you use weight loss medication or take supplements. These factors are not reflected in current protein recommendations, leaving some experts calling for a review of dietary protein guidelines, especially for older adults.

As well as how much protein you eat, you should also consider the quality of the protein sources you choose and how you distribute it in your daily meals.

Now read:

Everything you need to know about protein
The best sources of protein for vegetarians
Protein and carbs – get the balance right
How much protein to build muscle?
High-protein breakfasts
High-protein lunches
High-protein dinners
Best supplements for muscle growth
Best supplements for runners


This page was reviewed on 15 April 2025 by Kerry Torrens.

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All health content on goodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.

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