From The Dorito Effect by Mark Schatzker
. . . perhaps the most striking proof of such nutritional wisdom comes from a 1939 study in which a group of toddlers were put in charge of feeding themselves. They were offered 34 nutritionally diverse whole foods, including water, potatoes, beef, bone jelly, carrots, chicken, grains, bananas and milk. What each child ate, and how much, was entirely up to him or her.
The results were astonishing. Instead of binging on the sweetest foods, the toddlers were drawn to the foods that best nourished them. They ate more protein during growth spurts and more carbs and fat during periods of peak activity. After an outbreak of mononucleosis, curiously, they consumed more raw beef, carrots and beets. One child with a severe vitamin D deficiency even drank cod liver oil of his own volition until he was cured. By the end of the experiment, one doctor was so impressed with the toddlers’ health that he described them as “the finest group of specimens” he’d ever seen in their age group.
CBC radio interview with Mark Schatzker http://www.cbc.ca/player/AudioMobile/The%2BCurrent/ID/2666612993/