An introduction to protein

Protein is essential for a number of functions including growth, brain development, healthy bones and the production of hormones. Proteins are made up of ‘building blocks’ called amino acids. There are 22 amino acids in total of which eight (or ten for children) are termed essential because we cannot make them in our bodies and so have to get them from the food we eat.


Proteins are divided into two groups: animal and plant. Animal proteins, such as meat, cheese and eggs are sometimes referred to as primary proteins as they contain all eight essential amino acids and are considered to be the most important ones for growth. Plant foods rich in proteins include pulses, legumes, lentils, tofu and other soya products. As delicious and nutritious as these foods are, they are referred to as incomplete proteins because they don't contain all of the essential amino acids. However, as long as a varied, plant-based diet is eaten, vegetarians should have no problem achieving their protein requirements.


How much protein do you really need?

The crude measurement is 0.7g of protein for every kilogram of body weight. The average person easily reaches this protein requirement without even being on a high-protein diet. However, your personal needs will depend on your age, sex and level of activity.

The ‘Biological Value’ of protein:
In order to assess the quality of a protein, scientists measure the proportion of the amino acids that are absorbed, retained and used in the body to determine the protein's biological value (BV). The food source that has the highest biological value is whey protein, the second highest is eggs. Whey is a natural by-product of the cheese making process; when cheese is made, the whey is left behind. It is a complete protein because it contains all the essential and nonessential amino acids, particularly those important to cellular health, muscle growth and protein synthesis, which is why whey is favoured by body-builders and athletes. However, studies suggest that some of the health properties of whey may be compromised by the extensive processing most products undergo.

Chicken satay salad with gem lettuce, cucumber and pomegranate on a white plate

Why people follow a high-protein diet

There are some occasions when extra protein is needed, including childhood/adolescence (growth), pregnancy, lactation, intense strength and endurance training and certain illnesses. The elderly may also require extra protein.

Furthermore, many experts believe that a diet high in carbohydrates – refined ones in particular – is the main cause of weight gain and the modern obesity epidemic. As a consequence, high-protein (coupled with low-carbohydrate) diets have become increasingly popular, with the Atkins diet and Dukan diet among the most well-known. These diets typically allow you to eat unlimited amounts of all meat, poultry, fish, eggs and most cheeses, while carbohydrates are limited. A typical high-protein diet might consist of a breakfast of ham and eggs, lunch of cheese, meat, fish or an omelette and dinner consisting of meat or fish and vegetables.

Similarly, the Paleo diet has received considerable attention for its high protein principles. The idea behind the diet is that by sticking to a diet that mimics our hunter/gatherer ancestors, one that avoids carbohydrates, grains and other modern foods, you are eating just what you need to stay lean and avoid inflammatory conditions.

Research and safety

There is evidence to suggest that the body handles animal proteins differently from plant proteins and that reliance on purely animal proteins may lead to the development of several chronic conditions such as osteoporosis, heart disease, high blood pressure and some cancers. This has been supported by population studies and animal studies comparing vegetarians and omnivores.

In the short-term, high-protein, low-carbohydrate diets may reduce hunger and often reduce energy (calorie) intake, conferring some benefits for weight loss. High intakes of vegetable protein may have beneficial effects on cardiovascular disease and lipid profiles compared to animal sources. Before embarking on a high-protein diet, it is important to talk through the options with your GP or health professional.


Recipe inspiration

If you are concerned you're not eating enough protein, check with your doctor before changing your eating habits. If you do need to increase your intake, our delicious, nutritionist-approved recipes are perfect for a protein-boost.

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Read our expert guides on how to eat a balanced diet, try the best sources of protein or discover the best vegetarian sources of protein.

This article was last reviewed on 16 September 2019 by Kerry Torrens.

Kerry Torrens BSc. (Hons) PgCert MBANT is a Registered Nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food

Jo Lewin is a registered nutritionist (RNutr) with the Association for Nutrition with a specialism in public health. Follow her on Twitter @nutri_jo.


All health content on 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 health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

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