Protein is made from amino acids. Our bodies can make some of them, while the essential amino acids have to come from food. Plant foods contain all of the essential amino acids, but the proportions vary: a grain may be relatively low in one amino acid while a pulse supplies more of it.
Complementary proteins are foods whose amino-acid profiles balance each other. Familiar combinations include:
- beans with rice
- dhal with flatbread or rice
- hummus with pitta
- peanut butter on wholegrain toast
- lentil soup with bread
Legumes are generally rich in lysine, which is often present in lower amounts in cereals. Combining a varied range of foods therefore improves the balance across the diet.
Do they have to be eaten together?
No. You do not need to carefully pair complementary proteins at every meal. The British Dietetic Association says that essential amino-acid needs can be met across the day. The more useful habit is simply to eat enough food and include a variety of protein sources over time.
That might mean porridge and nuts at breakfast, hummus at lunch, and a lentil curry with rice for dinner. They do not need to be combined in one perfect plate for your body to make use of them.
What to focus on
Aim for variety rather than amino-acid arithmetic. Beans, lentils, chickpeas, tofu, tempeh, peas, nuts, seeds and whole grains can all contribute. The NHS recommends including beans, pulses and other proteins as part of a varied and balanced vegan diet.
People with higher protein requirements, restricted diets, poor appetite, or medical conditions may need individual advice from a registered dietitian.