The production and use of leaf protein.

The proposal that a new foodstuff should be made and used encounters different forms of scepticism from different groups of people. But every proposal will meet scepticism in some form. Although irrational scepticism, or ‘instant opposition’, may in practice be the most troublesome, it may be disregarded in the context of this meeting and the remaining forms may be arranged as a quasi-logical sequence of questions: Is a novel food needed? Would the one proposed contribute significantly to meeting the need? How would it be made? What would it be made from? How would it be used? What is its relationship to other comparable proposals? The first question is answered by the fact that we are holding this meeting and by Woodham’s paper, the second can be subdivided into three parts: Would the product be available in places where it is actually needed? Would it be feasible to make enough of it to be of practical importance? \%‘hat evidence is there about its nutritional value? Most of the people who are now in greatest need of extra protein live in the wet tropics. Furthermore, they do not live in urban areas, or even in the shanty-towns that are insidiously growing around them, but in country districts with poor communications. One very important practical need is therefore for a method of producing protein from a local source. The quickest and most practical way to increase the use of leaf protein in these regions is to encourage the use of leafy vegetables. Nevertheless, although most communities could with advantage eat more vegetables, an upper limit is set by human physiology. This limit can be circumvented by separating protein from fibre mechanically. Quantitatively, this method of making protein would be unrivalled in tropical regions with regular heavy rainfall. Even in Britain we can get 1-4 tons of extracted protein from a hectare in a year; this is as good as the protein yields claimed for soya or groundnuts in climates adapted to them, and we expect to reach 2 tons. In Mysore, 3 tons per hectare has already been reached. There has as yet been little agronomic work on leaf protein production and no work at all on breeding plant strains suited to this purpose. The amino acid compositions of protein samples from leaves of different species, ages and cultural background are similar (e.g. Pleshkov & Fowden, 1959; Chibnall, Rees & Lugg, 1963; Gerloff, Lima & Stahniann, 1965). I am uiiconvinced that any of the apparent differences are greater than the possible error in the determinations. This is not unexpected because what is loosely called leaf protein is a mixture