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 such important messaging roles in the body.
Protein is made up of long chains of smaller units called amino acids. These building blocks are put to use 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, tuna pots and turkey lettuce wraps.
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 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?
In addition to the important roles played by protein, ensuring you consume adequate amounts may help:
- Support recovery after exercise or injury
- Reduce muscle loss
- Help with weight management
- Curb appetite
- 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 may 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 depend on our own unique characteristics, like age, weight, gender, general health and physical activity levels. As does 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 protein needs, too. 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 to help counter the loss of muscle mass.
As we get older, 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 leads to frailty and increases the chance of a fall.
How much protein do I need?
In the UK, the Reference Nutrient Intake (RNI) is 0.75 gram/kg of body weight. This is the minimum amount and is based on an average sedentary adult. The following are minimum guidelines and 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
Does it matter what and when I eat protein?
Opting for high-quality protein is important. These sources contain all the essential amino acids, including leucine, which is key for synthesising muscle tissue. Eggs, yogurt and milk, as well as whey protein powder, soya milk and tempeh, are all useful sources.
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 one meal. In practical terms, this may involve two to three meals, each containing about 25-30g of high-quality protein.
People doing an intensive exercise programme may benefit from consuming protein after a workout, and similarly spacing their intake through the day.
Can I eat too much protein?
High intakes of protein had been thought to lead to bone loss and added strain on the kidneys, especially for older adults. However, more recent findings demonstrate a benefit for bone health, with higher levels of dietary protein posing a risk to kidney function only for those with existing kidney disease or impaired function.
This means that for the majority of healthy adults, long-term consumption of protein at 2 grams/ kg of body weight per day is considered safe.
How much protein we need is unique to us and depends on factors such as age, health status and how active we are. These factors are not reflected in current protein recommendations, leaving some experts suggesting the need for an increase in dietary protein from midlife.
As well as how much protein we eat, we should also consider the quality of the protein sources we choose and its distribution through the day.
Found this useful? Now read:
Everything you need to know about protein
The best sources of protein for vegetarians
High-protein breakfast recipes
High-protein lunch recipes
High-protein dinner recipes
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