Frank I. Katch


Santorio experiments breakthrough
in energy metabolism


Frederick Gowland Hopkins (1861-1947)
Hopkins rose to prominence in the early 20th century by other than normal academic channels. Beginning work at age 17 for an insurance company and then a railroad, he eventually enrolled in the Royal School of Mines and assisted in a private chemistry laboratory.  Hopkins qualified for membership in the Institute of Chemistry by attending lectures at London's University College. While studying medicine, he worked as a chemistry assistant at Guy's Hospital. Following graduation, Hopkins became a demonstrator in physiology at London University.  Sir Michael Foster, renown Professor of Physiology at Cambridge University, invited Hopkins to develop a research and teaching program in chemical physiology. 

By 1901, Hopkins had devised new experimental methods to isolate uric acid (thought to be related to protein breakdown).  Subsequent experiments showed how to make pure (crystalline) preparations of this compound.  In France, physiologist Francois Magendie (mentor to experimentalist Claude Bernard) had already demonstrated that an animal would die if fed a single foodstuff such as carbohydrate. Hopkin's breakthrough discovery isolated and identified the structure of the amino acid tryptophan, for which he shared the 1929 Nobel Prize in Medicine or Physiology. Hopkin's experiments proved that "unidentified accessory food factors" prevented the development of deficiency diseases. Rats sickened and died on a purified diet of sufficient energy, but thrived when fed a supplement of either 3 ml of milk (less than 4% of the whole food eaten) or an alcoholic extract of milk. Hopkins first proved that the "accessory food factor" (later called vitamins) had organic properties indispensable for maintaining good health. He stated: 

It is possible that what is absent from artificial diets and supplied by such addenda as milk and tissue extracts is of the nature of an organic complex (or of complexes) which the animal body cannot synthesize. But the amount which seems sufficient to secure growth is so small that a catalytic or stimulative function seems more likely.

Hopkins shared his ideas (Hopkins, 1906) about the need for supplementary nutrients to promote health: 

... no animal can live on a mixture of proteins, carbohydrates, and fats, and even when the necessary inorganic material is carefully supplied the animal still cannot flourish. The animal body is adjusted to live either on plant tissues or the tissues of other animals, and these contain countless substances, other than the proteins, carbohydrates, and fats. 

Physiological evolution, I believe, has made some of these well-nigh as essential as are the basal constituents of diet. Lecithin, for instance, has been repeatedly shown to have a marked influence upon nutrition, and this just happens to be something already familiar, and a substance that happens to have been tried. The field is almost unexplored; only is it certain that there are many minor factors in all diets, of which the body takes account. 

In diseases such as rickets, and particularly in scurvy, we have had for long years knowledge of a dietetic factor; but though we know how to benefit these conditions empirically, the real errors in the diet are to this day quite obscure. They are, however, certainly of the kind which comprises these minimal qualitative factors that I am considering. 

I can do no more than hint at these matters, but I can assert that later developments of the science of dietetics will deal with factors highly complex and at present unknown.

Hopkins both produced pioneering studies in nutritional biochemistry and collaborated with physiologist Walter Morley Fletcher (mentor to future Nobel Laurette A.V. Hill) to study muscle chemistry.  Their classic 1907 paper in experimental physiology employed new methods to isolate lactic acid in muscle.  Prior studies of stimulated muscle showed large concentrations of lactic acid in both stimulated and non-exercised muscle.  Fletcher and Hopkins' chemical methods reduced the muscle's enzyme activity prior to analysis to isolate the reactions. They found that a muscle contracting under low oxygen conditions produced lactic acid at the expense of glycogen (Fletcher & Hopkins, 1907).  Conversely, oxygen in muscle suppressed the formation of lactic acid.  The researchers deduced that lactic acid forms from a non-oxidative (anaerobic) process during contraction; during recovery in a non-contracted state, an oxidative (aerobic) process removes lactic acid with oxygen present.  A.V. Hill, 1922 Nobel Prize recipient, credited this experiment as the catalyst to subsequent research in muscle chemistry through 1925 (Hill, 1926).

Hopkins won honors -- first professor of biochemistry at Cambridge; knighthood (1925); Copley Medal of the Royal Society (1926); President of the Royal Society (1931); Order of Merit (1935); highest civilian prize -- and actively researched until his retirement, an admirable exemplar for Exercise Nutrition (Baldwin, 1972; Needham & Baldwin, 1949).

Experimental animals from Hopkins' classic studies that provided the crucial information about "accessory food factors" (vitamins) indispensable for maintaining good health. 


Baldwin, E. (1972).  Frederick Gowland Hopkins.  Dictionary of Scientific Biography, VI, 498.  New York, New York:  Charles Scribner's Sons. 

Fletcher, W.M. and Hopkins, F.G. (1907).  Lactic acid in amphibian muscle.  Journal of Physiology, 36, 247. 

Hill, A.V. (1926).  Muscular activity.  The Johns Hopkins University, School of Medicine. Lectures on the Herter Foundation, sixteenth course.  Baltimore, Maryland:  Williams & Wilkins. 

Hopkins, F.G. (1906).  The analyst and the medical man. The Analyst, 31, 386. 

Needham, J. & Baldwin, E. (Eds). (1949).  Hopkins and biochemistry. Cambridge, England:  W. Heffer. 

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