While ovo lacto vegetarians usually have adequate protein supply through the remaining protein sources from eggs and milk, the protein intake is critically evaluated in a vegan diet [Clarys et al, 2014].
For vegans, the same recommendations apply for protein intake as for omnivores. However, in the case of a vegan diet, sufficient nutritional knowledge and planning are needed to ensure adequate protein supply. On the one hand, the protein quantity has to be satisfied and, on the other hand, the protein quality must be largely optimized [Marsh et al., 2012].
Animal protein provides protein of high biological value while plant protein except for e.g. soy, quinoa and amaranth have one or more essential amino acids only in small amounts. For example, the lysine content in cereals is low and therefore a limiting factor for the protein usability of cereals and cereal products. It is therefore recommended to consume several different plant protein sources throughout the day in order to improve protein quality. For this purpose, vegans are expected to cover the protein requirements for the following foods: legumes (e.g. soybeans, chickpeas, lentils, kidney beans), whole grain cereals (e.g. brown rice, buckwheat, quinoa, amaranth), soy products (e.g. soy milk, soy yoghurt, tofu) and nuts and seeds [Marsh et al., 2012].
As can be seen in the table, vegans particularly benefit from the combination of cereals and legumes. This results, in part, in a higher biological value than cereals and legumes consumed isolated [Day, 2013].
| Protein source | Biological value |
|---|---|
| Wheat | 0.42 |
| Gluten | 0.25 |
| Rice | 0.47 |
| Corn | 0.46 |
| Millet | 0.20 - 0.30 |
| Soy protein isolate | 1.00 |
| Pea protein isolate | 0.73 |
| Chickpeas | 0.73 |
| Wheat flour + Pea protein | 0.82 |
| Wheat flour + Soy protein | 0.72 |
| Rice + Peas | 1.00 |
Biological value of different plant protein sources and combinations [modified by Day, 2013]
Literature
Clarys P, Deliens T, Huybrechts I, Deriemaeker P, Vanaelst B, De Keyzer W, Hebbelinck M, Mullie P. Comparison of Nutritional Quality of the Vegan, Vegetarian, Semi-Vegetarian, Pesco-Vegetarian and Omnivorous Diet. Nutrients 2014:6;1318-1332.
Marsh KA, Munn EA, Baines SK. Protein and vegetarian diets. MJA Open 2012;1:7–10.
Day L. Proteins from land plants – Potential resources for human nutrition and food security. Trends in Food Science & Technology 2013:32;25–42.
