Yardenman said:A little dirt never hurt anyone. But only in a generally hygenic culture.
Some nutritionists from Yale went on a field trip to China (decades ago, when that was more of an adventure). They were interested in "traditional" diets among farmers, because the variety of foods didn't seem likely to provide all the vitamins they were sure were needed.
Well, the diet of those farmers WAS as limited as the Yaleies had heard, and by all their scientific knowledge, SHOULD have given them all nutritional deficiency diseases. But they were quite healthy.
So the scientists went back to new Haven scratching their heads. They paid a bunch of undergrads to eat a test diet "exactly identical" to what the Chinese farmers ate. The kids got sick right away, exactly as predicted.
They fiddled around until they figured it out.
Their cooks were CLEANING all the vegetables very thoroughly before cooking them or serving them raw.
The farmers were only cleaning them FAIRLY well.
The small number of soil microbes in the small amount of soil remaining on the vegetables were providing the missing vitamins.
Take away the dirt, take away the vitamins.