EVENING DISCOURSES. 



FIRST EVENING DISCOURSE 

 Friday, September 3, 1937. 



GRASS AND THE NATIONAL FOOD 



SUPPLY 



BY 



Dr. R. E. SLADE. 



From earliest times men must have found considerable difficulty in the 

 food supply when living in large communities. As man has become more 

 civilised, and his life has become more organised, he has made mistakes in 

 dietetics — mistakes which a committee of the League of Nations has 

 investigated and now reported upon. 



There is now a ' newer knowledge ' of nutrition which will guide us in the 

 selection of our food — for the quality of our food is perhaps of greater 

 consequence to us than is the quantity. 



To the chemist Lavoisier belongs the credit of having first approached 

 human nutrition from the fundamental scientific aspect. His discovery 

 that the animal body is essentially a kind of furnace, in which the food 

 digested undergoes slow combustion and is ultimately converted into heat, 

 remains the chief corner-stone of the modern science of dietetics. 



Foods may be roughly classified into ' body workers and warmers ' 

 (essentially carbohydrates and fats), ' body builders ' (essentially protein), 

 and ' body protectors ' (essentially vitamins and minerals). The first are 

 required to maintain the body temperature above that of the surrounding 

 air, to supply the body with energy for carrying on the internal operations 

 of digestion, etc., and for doing external work. 



Proteins are needed for building up cellular tissues, both in growth and in 

 repair ; and the newer work on nutrition has demonstrated not only the 

 superiority of certain proteins for body building, but also something of the 

 role of vitamins and minerals for the efficient functioning of individual 

 organs, and for co-ordinating their activities. 



A food is evaluated as a supplier of energy by measuring the heat it gives 

 out when it is oxidised in the body. The chief suppliers of energy are the 

 carbohydrates (sugars and starch) and fats, though the proteins also 

 contribute their quota. The total energy value of human food is usually 

 measured in terms of calories, but for foods given to useful domesticated 

 animals like cows, sheep and pigs, a larger unit is employed — that of i lb. 

 of starch. The starch value, or ' starch equivalent ' of a food is a number 

 expressing how much of it acts as starch during digestion. 



Thus the S.E. of linseed cake is 72, i.e. 100 parts by weight of it supply 

 the same amount of energy as 72 parts of starch. One pound of starch is 

 equivalent to 1,861 calories. A similar unit is used for proteins. The 

 ' protein equivalent ' of a food expresses the percentage of the food which 

 plays the same part in the animal economy as pure digestible protein. 

 Thus linseed cake has a protein equivalent of 24, i.e. 100 parts of linseed 

 cake are equal in body-building value to 24 parts of pure digestible protein. 



