A Lecture ON THE PRACTICAL IMPORTANCE OF VITAMINES
Authors: F. G. Hopkins
Journal: BMJ (1919)

IN many departments of humian knowledge the teaching and guidance of science are accepted as final because in Ihese departments the knowledge arose in the first instance froimi scientific studies and from tllese alone.Progaress in suclh categories dependcs entirely upon controlled and re- e,orded observation or upon experiment, -ad these are tlle methods of science.It is otherwise, one inight be tempted to say, in regions wlhere mlankind can claim -abundant and-wcoumulated emppirical experience.In connexion witlh Ihis own nitri- ,tion man's experience lhas, nedless to -siy, been co- terminous with -his whole existence.Scienice may explain *hat experience, but is.unlikely, it might seem, to imaprove upon experience as a guide.It mnay stipply thcory, but where experience has been so great and so continuious it seems unlikely that it could do much-to guide practice.This consideration, consciously or subconsciously, accounts, I thiink, for a widespread feeling that the teachings of seience about our food supply are of academic interest 'enly.I am to deal, however, with some facts which indicate that, in one direction1 at least, practice, for lack of know- ledge, hias for a lonig time been in danger of going wrong.Experience mnight douibtless lhave eventually corrected the error; but it may be hoped that in this case scientific study will forestall experience, whicl is a much slower and more expensive teacher.So long as a commuunity can command not only a .ufficienicy of food, but also a variety of foods, and uses these foods in freslh condition, as nature ade tlhem, appetite and instincts (if unperverted) are usually sufficient to secure efficient nutrition for the individual.But whlen atural foodstuffs are treated artificially-whieni, for in- *tance, one kind 6f food material is fractionated, and the Aonsuimer presented witlh a part of it only; or when Aether n-mterial is dried or lheated for preservative or other purposes; or, again, when natural foods are sealed ep and kept for long periods, it by no means follows that the food materials any longer subserve proper nutrition, even tlhough they are eaten in sufficient quantity and satisfy the appetite.Now questions of diet are proverbially liable to stimulate quackery, and if I were hebre tb discuss the merits of natural " foods without giving objective facts I might be imspected of merely supporting certain doctrinaires-self, dubbed "food reformers "-whose--zeal outruns, their knowledge.There are facts, however, wlhich support the view thiat where commercial or otlher .enterprisestupplies tje public witlh articles of diet whicli have been treatecd *er "refined " so as to please the eye or to accord with a Lashion or convenience, it may be encouraging very wrong praetice.Related facts show that tlle public, when em- Aoying tinned or dried or preserved foods, should use them with discretium, and suppleEment them properly.ITo the naive view that the one important factor in 44trition is the quantity.eaten, the science of thle last oentury added one discrimiinative fact -namely, that quality must be considered as w'ell as quantitv, in so far that tlhe food eate m-ust in any case contain a certain wininimum of protcin.It tanglht that;..he esseutial con- mtituents of a diet which promotes proper nutrition are protein, carbohydrate, fat, and mineral salts, the organic aterials being always provided in rfcient amount to I supply the demands of the bodY for energy.WhIat we have lately learnt-though it is remarkable bow slowly came a recognition of the facts-is that, in addition to the above constituents.which our diets always ojntain in tangible and easily ascertainable amounts, an effieient diet mut also comprise other substances, of whiclh the elharacteristie is that thieir nutritive importance is out, '*_ elivered in the course of Imperial Studies Lectures on Physiology and National Needs.atKing's College.London., February 19tlh. 1919.