Since its discovery in the early part of this century, we have learned a great deal about vitamin A. Among other things, we now know that this once-mysterious compound is essential for normal growth and development, that it plays a central role in maintaining the body's skin and epithelial cells, and that it forms part of the two pigments needed by the retina to help the eye adjust to varying degrees of light. Yet, as late as 1907--when a young biochemist named Elmer McCollum arrived at the University of Wisconsin to take an instructor's post--very few scientists even suspected the existence of such compounds.
Scientists knew relatively little about nutritional needs in those days. True, in the 1880s a few researchers had already begun investigating the link between diet and certain diseases, such as beriberi. And by 1906, the English biochemist, Frederick Gowland Hopkins, was looking into what he termed "accessory food factors." But in general, the scientific community believed that all dietary needs could be met by proper amounts of carbohydrates, proteins, fats, minerals and water. The concept of trace nutrients was largely unknown.
At the time, McCollum himself had no particular interest in nutrition. Born and raised in Kansas, he'd recently received his doctorate from Yale University. McCollum's primary interest, however, was inorganic chemistry. He'd switched to biochemistry (then known as agricultural chemistry), simply because no position was immediately available in his chosen field.
In 1907, when McCollum reported to the University's Agricultural Experiment Station, the department was headed by Stephen Babcock (1843-1931), one of the country's most widely respected biochemists, then close to retirement. A research study was already in progress, one designed by Babcock to study the effects of different single-grain diets on dairy cattle. Because the three grains being tested were chemically similar, it was assumed they would have similar dietary effects. To the research team's surprise, however, only the corn-fed cows remained healthy; those fed wheat or oats failed to thrive. McCollum, the newest member of the team, was immediately intrigued. Even in foods that seemed similar, he reasoned, there might be some undiscovered difference in their fundamental structures.
Before long, McCollum was designing his own nutritional studies. Because he felt that dairy cattle were too cumbersome to work with, he set up a colony of albino rats, the country's first such colony devoted to experimental research. In his own laboratory--and with the help of a recent University of Wisconsin graduate named Marguerite Davis --began the studies that were soon to make him famous.
By 1913, McCollum was able to report that laboratory rats eventually stopped growing when put on diets in which lard or olive oil was the only source of fat. These same rats, however, quickly resumed normal growth when fed "the ether extracts of eggs or butter." McCollum concluded that butterfat and egg yolks must contain some growth-promoting factor missing in other fats. His findings were very similar to those of another research team-- Lafayette B. Mendel (1872-1935) and Thomas B. Osborne at Yale University--but, since his paper was submitted earlier and contained several crucial steps missing from the Mendel and Osborne findings, he is generally credited with the discovery.
Within two years, McCollum had isolated the growth-promoting factor and named it fat-soluble A to distinguish it from a water-soluble factor (previously discovered by Christiaan Eijkman in rice polishings) that he termed water-soluble B. Fat-soluble A was soon to be known as vitamin A--the first vitamin actually to be named and described. Water-soluble B is now known, of course, as vitamin B.
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