Defining protein

Proteins are basic constituents in all living organisms. Within the body, proteins are necessary for enzymatic activity, immunity, cell signalling, and muscle function, repair and transport processes and as structural elements in cells. Dietary proteins provide nitrogen and, when needed, energy (4 kcal/g)  ( NNR 2023 (pdf) ).

The building blocks of proteins are amino acids ( Present Knowledge in Nutrition 2020 ). Indispensable amino acids (IAAs) are those that the human body cannot synthesise to meet its needs and therefore must be supplied through the diet (  EFSA 2012 (pdf) ).  

In sensitive individuals, allergic reactions can be triggered by proteins present in gluten-containing cereals, crustaceans, fish, eggs, peanuts, soybean, milk, nuts, celery, mustard, sesame, lupin and molluscs. For example, gluten, a protein present in wheat, rye and barley and many other cereals, can trigger coeliac disease, a life-long systemic autoimmune disorder. For individuals with food allergies or coeliac disease, management typically involves avoiding allergenic foods or adhering to a gluten-free diet (  EFSA 2014 ).  

Dietary sources of protein

Almost all foods of animal or plant origin contain proteins, although their protein content and amino acid composition differ broadly. Tables 1a and 1b show examples of protein content in some animal- and plant-derived raw foods ( Fineli database ).

Table 1a - Average protein content in and % of food energy in some animal-derived raw foods

Table 1b - Average protein content and % of food energy in plant-derived raw foods

Cereal proteins are relatively low in certain IAAs (such as lysine) while legume proteins tend to lack sulphur-containing amino acids. In a varied diet, different plant proteins can complement each other, providing a balanced combination of IAAs. Unprocessed plant protein sources contain compounds that interfere with the digestion of their protein, making them less digestible and less bioavailable than animal-sourced proteins. However, in practice, this difference in protein quality might be less critical in diets containing a range of protein sources ( NNR 2023 (pdf) ). In regions where diets are based on single staple foods (e.g. millet, sorghum, cassava) and dietary diversity is low, there is a risk of dietary protein inadequacy  ( WHO/FAO/UNU 2007 ).  However, most Western diets, including those in Europe, generally provide high-quality protein owing to the wide variety of plant food consumed and the considerable presence of animal foods. 

Labelling of protein in the EU

The protein content of a food is among the mandatory information to be provided in the nutrition declaration on food labels, according to Regulation (EU) No. 1169/2011 ( EU 2011 (pdf) ). For labelling purposes, the reference intake for protein of an average adult (8400 kJ/2000 kcal) is 50 g/day. Reg. (EU) 1169/2011 also lays down rules for the mandatory declaration on labels of pre-packed foods and in non-prepacked foods of substances or products causing allergies or intolerances (discussed in Defining Protein above); the regulation applies also to foods served in restaurants and cafes. In addition, a Commission guidance document ( EC 2017 ) has been adopted, aiming to assist consumers, businesses and national authorities to better understand the requirements of Regulation (EU) 1169/2011 regarding food allergies and intolerances.

Protein nutrition claims are permitted, according to Regulation (EC) No 1924/2006 ( EC 2006a (pdf) ), as follows:

• Source of protein: 'A claim that a food is a source of protein, and any claim likely to have the same meaning for the consumer may only be made where at least 12% of the energy value of the food is provided by protein'
• High protein: 'A claim that a food is high in protein, and any claim likely to have the same meaning for the consumer may only be made where at least 20% of the energy value of the food is provided by protein.'

Certain health claims for food products that are a source of protein are also permitted, relating for example to the capacity to contribute to growth and maintenance of muscle mass and the capacity to maintain normal bones and normal growth and bone development in children. The list of all authorised and non-authorised nutrition and health claims is accessible at the relevant EU Register ( EU Registry on nutrition and health claims ).

Protein intake: effects on health

National and international institutions have assessed the effects of protein intake on health, especially on the development of non-communicable diseases (NCDs). The statements or opinions from these institutions, as well as the strength of the supporting evidence, are shown in Table 2.

Table 2 - Health effects by food- and health-related organisations

Recommended intakes of dietary protein

EFSA's Scientific Opinion on Dietary Reference Values  (DRV) for protein, EFSA establishes Average Requirement (AR) and Population Reference Intake  (PRI) values for various life stages (infants, children, adults) and physiological conditions (pregnant and lactating women). However, data was insufficient to establish DRVs or a Tolerable Upper Intake Level (UL) for protein.

For adults with moderate physical activity, recommended protein intake ranges from 0.80-0.83 g/kg. Higher intakes are recommended for children, pregnant/lactating women, and sedentary older adults, who are more at risk of deficiencies ( WHO/FAO/UNU 2007 ). 

Tables 3, 4 and 5 outline recommendations for adults/older adults, pregnant/lactating women, and infants/children/adolescents.

The recommended intakes are termed differently because different food- and health- related organisations use different criteria. Frequently used terms are: Average Requirement (AR), Population Reference Intake (PRI), Safe Level of Protein (SLP), Recommended Dietary Allowances (RDA); Dietary Reference Value (DRV). 

Table 3 - Dietary recommendations for adults and older adults by food- and health-related organisations

Table 4 - Dietary recommendations for pregnant and lactating women as by food- and health-related organisations

Table 5 - Dietary recommendations for infants, children and adolescents by food- and health-related organisations

Protein intake across European countries

In most European countries, the main contributors to dietary protein intake in adults are meat and meat products, followed by grains and grain-based products, and milk and dairy products. These three food groups contribute about 75% of protein intake across most EU Member States ( EFSA 2012 (pdf) ).

Table 6 compilesprotein intake data from food and nutrition surveys conducted in European countries. While differences in survey methodologies and age group categorisation prevent direct comparisons, it is possible to observe that many EU citizens have dietary protein intakes above the recommended intake levels. 

Table 6 - Overview of protein intake in European countries

Disease burden related to protein intake

In general, protein-deficient diets often lack other nutrients as well. Protein-rich foods contain a variety of micronutrients, including vitamins, minerals and trace elements. Deficiencies in these, coupled with suboptimal protein and energy intake, contribute to different forms of protein-energy malnutrition. Determining the societal and economic burden strictly related to protein deficiency in populations is challenging (and ref here). Protein-energy malnutrition is more prevalent in low-income countries in the presence of food scarcity and other adverse environmental factors (e.g. infections). In high-income countries, protein-energy malnutrition is primarily observed in hospitalised patients due to underlying diseases or among older adults, where it is often linked to sarcopenia (a condition characterised by loss of skeletal muscle mass and function ( Coelho-Junior, H. J.et al. 2022 ). 

In high-income countries, average population protein intake typically exceeds recommended levels. While many food and health organisations have issued opinions/statements linking protein intake to the development of NCDs, the associated health effects are not easily quantifiable. Consequently, the specific health and societal burden linked to protein intake has not been estimated.

Policies addressing protein intake

There are some policies that are specifically addressing, directly or indirectly, protein intake, protein rich-foods and protein quality (Table 7).

Table 7 - Policy recommendations or of implemented policies to address protein intake

References

Overview of the references to this brief