Protein: role, sources and recommended intakes
What are proteins?
Proteins make up one of the three major groups of macronutrients, together with carbohydrates and fats, i.e. one of the constituents of foods that contribute to energy intake.
Proteins are manufactured by our bodies from amino acids. There are many amino acids, but only 20 are used to synthesise proteins in our bodies. For this reason, they are known as "proteogenic".
These 20 amino acids include:
- 11 that can be produced by our bodies, such as glycine, alanine, etc.
- 9 that must come from food, as our bodies cannot synthesise them in sufficient quantities. These are known as "essential" amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
What roles does protein play in the body?
Protein has a number of vital functions in the body:
- It provides structure by contributing to the renewal of muscle tissue, scalp and body hair, nails, bone matrix, skin tissue, etc.;
- It is involved in many physiological processes, for example in the form of enzymes, haemoglobin, hormones, receptors and antibodies.
Which foods contain protein?
There are two types of protein:
- Animal proteins come from meat, fish, eggs, milk and dairy products.
- Plant proteins come mainly from oilseeds (peanuts, almonds, pistachios, etc.), pulses (chickpeas, lentils, beans, etc.) and cereals.
Proteins can be found naturally in food or be added for nutritional purposes, such as in special foods for infants or the elderly, or for technical/functional reasons such as the gelling property of egg white used in mousses, for example.
>> See the list of foods that are highest in protein in the CIQUAL table
What are the differences between animal and plant proteins?
- Animal proteins are generally higher in essential amino acids than plant proteins. They are also slightly more digestible than plant proteins.
- Plant proteins may contain limited amounts of certain essential amino acids. For example, cereals are low in lysine and pulses are low in sulphur-containing amino acids (cysteine and methionine). Nevertheless, in France, energy and protein intakes are in line with the dietary reference values. Moreover, the sources of protein are sufficiently diversified to allay any fears about inadequate intake. There is therefore no need to recommend consuming a systematic combination of cereals and pulses.
How much protein is needed every day?
In 2007, the Agency determined the population reference intake for protein in healthy adults to be 0.83 g/kg/d.
In 2016, the Agency specified that the share of protein in daily total energy intake (TEI) should be between 10% and 20% for adults. Reference intake ranges were also defined for other populations (children, pregnant or breastfeeding women, the elderly, very physically active people).
Given the lack of available data, it has not been possible to define an upper intake level for protein.
Can vegetarian diets ensure an adequate protein intake?
By following the main daily dietary guidelines listed below, adult vegetarians (excluding pregnant or breastfeeding women, the elderly and very physically active people) can meet their protein needs:
- Fruit and vegetables: 700 g/d
- Pulses: 75 g/d (lacto-ovo vegetarians) or 120 g/d (vegans)
- Starches and bread: 170 g/d, including at least 120 g/d whole grains or sources of fibre (lacto-ovo vegetarians), or 250 g/d, including at least 120 g/d whole grains or sources of fibre (vegans)
- Oilseeds: 65 g/d (lacto-ovo vegetarians) or 50 g/d (vegans)
- Analogues of fresh dairy products: 350 g/d (lacto-ovo vegetarians) or 270 g/d (vegans)
- Brewer’s yeast: 10 g/d (lacto-ovo vegetarians) or 15 g/d (vegans)
- Milk: 450 ml/d, eggs: 30 g/d, cheese: 50 g/d (lacto-ovo-vegetarians)