Many people think that it is difficult to obtain sufficient protein whilst following a vegetarian diet. However, this is simply not true, as there are plenty of excellent protein sources for vegetarians, and in actual fact most meat-eaters consume much more protein than their bodies require.
Protein requirements for humans are 40g-50g per day. However, the World Health Organization (WHO) is among many organisations to suggest that in the West we now consume considerably more protein than is considered necessary or optimal for health. A typical UK protein intake is 60-80g of protein a day. According to the Healthy Planet Eating Report published in 2010 (based on research carried out at Oxford University) meat eaters get more protein than is recommended, vegans get less than is recommended, whereas pescatarians and vegetarians’ diets are in line with protein recommendations. We therefore shouldn’t be too concerned about whether or not we are getting enough protein as the vast majority of us will have a perfectly adequate intake. However, it’s important to note that not all protein sources provide the same ‘quality’ of protein. I’ll therefore give a quick biology lesson to explain what protein is and how different proteins differ.
Proteins are basically long chains of amino acids. Different proteins are made up of different combinations of amino acids. Living organisms require 20 different amino acids to make the proteins necessary for survival. The human body can make some of these amino acids itself but the others have to be obtained from food. Consequently, the ‘quality’ of dietary protein depends largely upon which amino acids it contains. A protein can be considered to be higher quality if it contains a higher proportion of the eight ‘essential’ amino acids that have to be obtained from food. Proteins that contain all the essential amino acids are said to be ‘complete’ or ‘first class’ proteins.
Plant proteins are less complex than animal proteins which means they generally contain fewer essential amino acids. Vegans may therefore benefit from combining different plant protein sources, for example, by eating baked beans on toast, or a bean and nut salad, or a lentil soup served with bread. Of all the vegan proteins, soya is one of the few which is ‘complete’ – so this should be an important part of any vegan diet.
A numerical measure of protein nutritional quality is given by the Protein Digestibility-Corrected Amino Acid Scoring (PDCAAS) method. This takes into account the essential amino acid profile of a food, its digestibility, and its ability to supply essential amino acids in amounts required by humans. Egg white, chicken and Quorn pieces all have the optimum score of 1. Soya protein is one of the highest quality plant proteins, with a score of 0.94.
Below I’ve listed the top eight vegetarian protein sources and have given an indication of protein concentration and quality for each. The protein contents were obtained direct from food package labels. For some of the more general products like cheese and soya burgers, I gave an average of the labels I could find, since different products will vary slightly.
For example: Quorn mince (15g/100g), Quorn pieces (14g/100g) Quorn sausages (7g per sausage)
The mycoprotein found in Quorn products was discovered by scientists looking for a new protein source back in the 1960s, when they were looking for a solution to predicted global food shortages. Although the mycoprotein itself is vegan, all Quorn products contain a small amount of egg white, and most also contain milk ingredients, so they are not vegan. Quorn is a complete protein since it contains all eight essential amino acids. The PDCAAS for mycoprotein is 0.91, fractionally behind beef at 0.92. Because of the egg albumen in Quorn pieces, the PDCAAS for these is 1.
For example: Milk (4g/100ml), cheese (21g/100g), yoghurt (6g/100g)
These products are known as ‘first class’ protein foods because they contain all eight essential amino acids. The PDCAAS for casein, the protein found in milk, is 1. Milk is also a good source of calcium, vitamin A, vitamin B12 and vitamin D.
One egg provides about 7g of protein. Like dairy products, eggs contain all the essential amino acids. The amino acid profile of egg protein is considered to be optimum and therefore the PDCAAS is 1. Eggs also contain vitamin A, vitamin D and vitamin B12. There is no longer a recommended limit on the amount of eggs you should consume per week, since it was discovered that consuming saturated fat causes cholesterol to accumulate in our bodies (not consuming cholesterol, which is found in eggs).
4. Soya products
For example: Tofu (17g/100g), soya burgers (10g/burger), soya sausages (8g per sausage), soya milk (3g/100ml)
Soya protein is one of the few plant proteins that contains all of the essential amino acids. It has a high PDCAAS of 0.94. Soya products are great for vegetarians and vegans, as they provide high quality plant protein and are generally low in fat.
For example: Hazelnuts (17g/100g), cashews (20g/100g), walnuts (15g/100g), peanuts (14g/100g), peanut butter (24g/100g)
These do not contain all eight essential amino acids but can be complemented by other foods. Nuts are also good sources of vitamins E, vitamin B2, folate, fibre, and important minerals.
For example: Baked beans (19g per standard-size can of Heinz), chickpeas (7g/100g), lentils (5g/100g), Houmous (7g/100g)
These contain a higher proportion of protein than most other plant foods and they are low in fat. Their PDCAAS is usually between 0.5 and 0.7. As well as being high in protein they are also a great source of fibre, vitamins and minerals. They can also count as one of your five-a-day! However they are deficient in the essential amino acid methionine so do not provide ‘complete’ protein.
For example: Bread (4g per slice), pasta (12g/100g), cous cous (15g/100g), oats (11g/100g), rice (8g/100g), Flapjack (6g/100g)
The proteins found in grains and cereals tend to be deficient in the essential amino acid Lycine. The PDCAAS for these products tends to be between 0.4 and 0.6. However, most people tend to eat a lot of bread, pasta and cereal products, so we generally obtain a lot of protein from these sources.
For example: Pumpkin seeds (33g/100g), seasame seeds (18g/100g), sunflower seeds (20g/100g), linseeds (22g/100g)
Seeds are also good source of vitamin E and contain a range of other useful vitamins and minerals.