In the 1920s and 30s, a Chicago pediatrician named Clara Davis did a remarkable experiment/demonstration: Letting young children choose their own food. About eleven children chose from a list of 30 little-processed foods — including sour milk, the only bacteria-rich food on the list — and could eat as much of each one as they wished. The choices included peaches, beef, carrots, beets, barley, bone marrow, pineapple, cabbage, lettuce, potatoes, and sweet breads. Many of the foods were supplied both raw and cooked. The experiment lasted about 6 years.

The main result was that the children were very healthy:

There were no failures of infants to manage their own diets; all had hearty appetites; all thrived. Constipation was unknown among them and laxatives were never used or needed. Except in the presence of parenteral infection, there was no vomiting or diarrhea. Colds were usually of the mild three-day type without complications of any kind. There were a few case of tonsillitis but no serious illness among the children in the six years.

Some of them were malnourished at the start of the experiment; all recovered. One had rickets and was offered cod liver oil. He drank a little bit of it while sick but after he recovered never drank it again.

Davis’s observations support the idea that we have inborn desires that help us choose what to eat. Davis emphasized that there was great variation from one child to another in what they ate — as Weston Price noted a great variation from one healthy community to the next in what they ate. She didn’t give details, however. The notion that our desires, given Stone-Age surroundings, help us choose a healthy diet is what led me to the umami hypothesis. It started with the idea that in the Stone Age our liking for complex, sour, and umami flavors caused us to eat food with more bacteria than fresh food. High-bacteria food tasted better than low-bacteria food; it was more sour, more umami, and had a more complex flavor. Suggesting that we need to eat bacteria to be healthy.

In a clever series called 10 Mysteries of You: Ten things we don’t understand about humans in New Scientist, Australian science writer Emma Young includes some obvious ones (blushing, altruism, dreams, art) but ends her list with a surprise: nose-picking. This had not occurred to me:

It is possible that ingesting nasal detritus might help build a healthy immune response – after all, researchers investigating the hygiene hypothesis have built a large body of evidence indicating that lack of exposure to infectious agents can increase one’s susceptibility to allergic diseases.

This seems to be Young’s idea rather than that of the scientist she spoke to. She has her hygiene hypothesis stuff wrong. The original hygiene hypothesis was indeed that lack of exposure to infectious agents can increase allergies — but the data later collected did not support this. More infections in childhood did not correlate with less allergy. What did seem to help was exposure to dirt. Apparently the dirt was helpful whether or not it was infectious (= contained something that could make you sick). The nose-picking data (kids pick their nose a lot and sometimes eat the stuff) does make sense given my umami hypothesis, which says that exposure to bacteria is good for us. You couldn’t get sick from eating what comes out of your nose but as it leaves your nose foreign bacteria grow on it; so eating your snot is a way to introduce foreign bacteria into your digestive system. Which the umami hypothesis says is needed for health.

Do kids who eat more fermented food eat less snot? As I posted earlier, since I started eating lots of fermented food, my desire for fancy restaurant food has gone way down.

Thanks to JR Minkel.