Babcock teamed up with fellow UW researchers Edwin B. Hart, Harry Steenbock and E.V. McCollum to find out what was missing. The team found that when milk, butter or cod liver oil were added to the inadequate diets, cows were healthier. The question was, why?
McCollum analyzed the milk and butter. He extracted the fats, the lipid-soluble fraction, from the water. As we now know, some vitamins dissolve well in water. Other vitamins dissolve in fat.
McCollum named the lipid-soluble part "A" and the water-soluble part " B." Those names remain with us today. Vitamin A was the first vitamin discovered in the fats. The first water-soluble vitamin was named B1, also known as thiamin.
As a glance at the nutrition facts on a box of breakfast cereal will tell you, many more vitamins were subsequently discovered. Other important fat-soluble vitamins include E, D and K. Many of the B vitamins are numbered, like B6 and B12, and also carry other names (pyridoxine, cobalamin).
A century after Hart's group published their discovery, researchers are still putting together the vitamin puzzle. For example, we know that we need vitamin D for strong bones, but we are still learning how it is important to the immune system and even to mental health. UW-Madison researchers Margaret Clagget-Dame, Hector F. Deluca, Colleen Hayes and J. Wesley Pike and others are still working to understand just how vitamins like A and D work in the human body.
Those long-ago cow studies led to great strides in human nutrition. But what did they tell us about the needs of cows?
As it turns out, with their more complex digestive systems, cows can manufacture many of the vitamins that we have to get from food. Like humans, cows make vitamin D just by spending time in the sun. Bacteria in the cow digestive tract make many B-vitamins. Cows' livers and kidneys produce vitamin C. So, vitamin-wise, cows clearly have a leg up.
Of course, as that early research showed, cows need to get some vitamins from their feed. Vitamins A and E are especially important. Adequate (but not higher) amounts of vitamin A may improve the health of mammary glands. Vitamin E has been linked to decreased mastitis.
Source: UW-Madison CALS