Discussing protein in the diet
Meat, fish, eggs, milk and cheese contain proteins with broadly the same amino acid composition as those found in our bodies. Digestion breaks these proteins down into amino acids, which are then available for reuse in roughly the proportions we need to build new proteins.
If particular amino acids are in short supply in our diet, we can make some of them from other molecules we eat. However, humans cannot make ten so-called ‘essential’ amino acids, so they come only from our diet. Essential amino acids include phenylalanine and tryptophan.
Vegans do not eat anything derived from animals, which means they have to get essential amino acids from other food sources. Some plant foods – including soya, quinoa and hemp – contain all the essential amino acids.
Meat is an important source of protein for many people around the world (download our ‘Probing proteins’ infographic). The global appetite for it is growing, which is putting more pressure on food production: feeding crops to animals is much less efficient than eating crops ourselves. For example, the least energy-efficient plant food uses around one-tenth as many fossil fuels as the most energy-efficient factory farming of meat.
The search is on for supplements or substitutes for meat that could help humans to avoid eating animals, ease pressure on cropland or simply offer healthier alternatives – especially to red meat, which includes saturated fat as well as protein. You can already buy meat substitutes made from a protein-rich fungus. In 2013, the first burger grown from cow stem cells was cooked and eaten. Protein powder made from farmed insects could also be a protein source of the future.
Questions for discussion
- Can you list three pros and three cons of using land to raise livestock?
- Are lab-grown burgers a promising innovation or an expensive diversion from feeding the world?
- Billions of people already eat insects regularly. Would you? Why?
- Proteins issue v2 [PDF 15MB]