There are still a lot of prejudices about vegan and vegetarian lifestyles, including the idea that a plant-based diet does not provide sufficient protein. In this article, I investigates this claim and shows that plant-based nutrition is perfectly suitable to meet everyone’s protein requirements.
What are proteins?
Proteins are complex chemical compounds consisting of many individual amino acids. The human body uses 21 amino acids for protein production, of which at least 9 cannot be produced by the body itself. These are called essential amino acids. A supply of these amino acids via dietary proteins is therefore vital for the maintenance of the body’s own protein structures.1 2
Functions of proteins
The functions of proteins inside the human organism are manifold. Their most important function is the construction of body tissue. Among other things, structural proteins serve as core building blocks for muscle, nerve, and connective tissue. Mass transport within the body, on the other hand, is carried out by transport proteins such as haemoglobin – a constituent of blood. The antibodies of the immune system and the protein fibrinogen, which facilitates blood clotting, belong to the class of protective proteins. Many hormones and enzymes, which control important processes in the body, are also proteins.3 4
According to the committee of the European Food Safety Authority (EFSA), the daily recommended values for the protein intake of mixed foods are as follows:
- Adults and the elderly:0.83 g per kilogram of body weight
- Infants, children and adolescents: depending on their age, between 0.83 g and 1.31 g per kilogram of body weight
- Pregnant women:additional intake of 1 g, 9 g and 28 g per day for the first, second and third trimester of pregnancy, respectively.
- Breastfeeding mothers: additional intake of 19 g per day during the first 6 months of breastfeeding, 13 g thereafter.5 Protein deficiencySince proteins are involved in the construction, function, and metabolism of all living cells and tissues, a deficiency leads to various disorders of bodily functions. In adults, an insufficient supply of protein can lead to a weakened immune defence, reduced wound healing, and a reduction in muscle mass.6 During childhood, mental impairment can also occur. However, protein deficiency is extremely rare in developed countries, although it is more common in developing countries whose populations are affected by malnutrition.7 Foods rich in proteinAmong vegetables, pulses (lentils, peas, and beans – and, above all, soya beans) and cereals (rice, oats, millet, wheat, spelt, rye) are of particular importance as protein sources. Soya products such as tofu and tempeh are also regarded as foods that are high in protein. Pseudocereals (amaranth, buckwheat, quinoa), nuts, almonds, and seeds also contain especially high amounts of protein.8FoodProtein content per 100 gFoodProtein content per 100 gSoya productsCereals and pseudo cerealsTextured soya protein21 gOats17 gTempeh20 gRye flour (whole grain)11 gTofu, firm15 gWheat flour (whole grain)9.5 gSilken tofu7 gQuinoacooked: 4.5 g (raw 14 g)Soya yoghurt4 gAmaranthcooked: 4 g (raw: 13.5 g)Soya milk4 gMilletcooked: 3.5 g (raw 11 g)PulsesNuts & seedsSoya beanscooked: 11 g (raw 36.5 g)Hemp seeds, hulled31.5 gLentilscooked: 9 g (raw: 25 g)Pumpkin seeds30 gChickpeascooked: 9 g (raw: 25 g)Peanuts26 gBlack turtle beanscooked: 9 g (raw: 24 g)Almonds21 gWhite beanscooked: 8 g (raw: 24 g)Sunflower seeds19 gGreen peascooked: 6 g (raw: 23 g)Cashews18 gKidney beanscooked: 5.5 g (raw 22.5 g)Sesame seeds17 gMiscellaneousNutritional yeast43 gPortobello mushrooms4 gSource: United States Department of Agriculture: USDA Food Composition Databases9 Quality of food proteinsThe contribution that protein from food makes to human nutrition depends on several factors. In addition to the protein content of the food, the digestibility and amino acid composition of proteins are important as well.10Biological value of proteinBoth animal and vegetable proteins contain all essential amino acids. They differ, however, in terms of the amounts they contain.11 The more the composition of amino acids corresponds to the human organism’s needs, the higher the biological value of a food protein. If the biological value of a protein is higher, less of it needs to be consumed in order to meet protein requirements as it is better suited to be converted into the body’s own protein.12 13 On average, proteins from animal products have a higher biological value than vegetable products, with exceptions including, for example, soybeans, potatoes, rice and rye.14 15 However, the biological value is increased considerably by combining different foods, as their respective amino acids complement each other. What is important is not the profile of amino acids in a single meal, but rather the distribution of amino acid supply across the whole day.16 17 If, during the course of their day, a person consumes enough protein from a wide variety of vegan protein sources – such as pulses and wholemeal cereals, or pulses and nuts or seeds – as well as enough calories,18 protein requirements can easily be met with plant foods.19 20 Digestibility of vegetable protein sourcesA useful measure of digestibility is the ‘protein digestibility-corrected amino acid score’ (PDCAAS), which takes into account not only the amino acid composition of the protein but also its digestibility.21) The higher the PDCAAS, the more easily and more completely the protein can be digested and the less protein needs to be consumed in order to cover protein requirements. Proteins of animal origin are usually more digestible than vegetable proteins as dietary fibre and robust cell walls contribute to the reduced digestibility of most vegetable proteins.22 However, the digestibility of many plant sources of protein is still relatively good and can be significantly increased by higher processing and proper chewing. The following methods of preparing pulses and cereals, for example, increase their digestibility and thus the absorption of vegetable protein:
- Cooking (cooking time varies depending on the type of pulse/cereal; cooking in a pressure cooker is particularly effective in terms of enhancing digestibility)
- Shredding, for example, in a food processor or blender
- Soaking in water (the soaking time and amount of water varies, depending on the type of pulse/cereal)23 Plant-based sources of protein are healthier than their animal counterpartThe biological value and digestibility of food are almost meaningless when it comes to determining how healthy a particular food is. Vitamins, minerals, dietary fibre, phytochemicals, carbohydrates, and unsaturated fatty acids also play an important role. In this regard, plant protein sources usually have an edge over animal-based proteins, as the latter often contain many unhealthy saturated fatty acids. According to a study published by Harvard Medical School in 2016, an increase in the intake of vegan protein was associated with a lower mortality rate. By increasing the amount of calories sourced from plant protein by just 3%, participants decreased their risk of all-cause mortality by 10% during the study period. Solely in relation to cardiovascular diseases, the mortality risk dropped by another 2 percentage points. On the other hand, the risk of the subjects dying from cardiovascular disease increased by 8% if the intake of animal protein in their diet increased by 10%.24Researchers at the University of Massachusetts also recently discovered that the source of protein – whether it is meat, fish, dairy products or pulses – is irrelevant in terms of building muscle strength and muscle mass.25 Protein supply for vegans and vegetariansLacto and ovo-lacto vegetarians consume ample amounts of essential amino acids if they consume the recommended amount of protein and calories. Similarly, the US-based Academy of Nutrition and Dietetics has stated that a well planned vegan diet can meet all dietary recommendations and ensure an adequate protein supply.26Various nutritional associations from other countries – such as the National Health and Medical Research Council in Australia27 and the Portuguese National Programme for the Promotion of Healthy Eating28– also share this view. Since vegans usually consume less food energy than omnivores and lacto or ovo-lacto vegetarians, their consumed protein amounts are usually closer to the recommendations of nutritional associations – the average person in western industrialized countries often exceeds the recommendations.Although there is a risk of protein deficiency if too few calories are consumed on a vegan diet, protein requirements can certainly be met by plant-based proteins. The consumption of a wide range of plant foods and a sufficient intake of calories are key. ProVeg tips for optimal plant-based protein supply
- A vegan diet can provide a sufficient supply of protein if a broad selection of vegetable protein and a sufficient intake of calories is ensured.
- Pulses – especially soya products – constitute important sources of protein in a plant-based diet and should be eaten daily. In combination with proteins from cereals and nuts or seeds, they help to provide an optimal amino acid profile. It is sufficient to eat the different sources of protein throughout the day, rather than during a single meal.
- The different methods of preparation (cooking, mixing, soaking) of vegetable foods increase their digestibility and thus the absorption of vegan protein.
- There is an increasing awareness that plant proteins are healthier than animal proteins. The consumption of plant protein instead of animal protein is associated with lower mortality rates.
|1.||↑||Institute of Medicine of The National Academies (2005): Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids, p. 593|