Here is interesting early 20th century research into nutrition and physical degeneration, particularly dental decay. The researcher was inspired by the superior nutrition and good dental health of people not excessively exposed to the modern industrialized food system (In the parlance of the times, “primitives”). His research showed that replacing a modern diet with good nutrition (high vitamin / lower calorie foods) creates healthy saliva that reinforces tooth enamel and gum strength in the mouth, and can even repair tooth decay.
He found it very important for human physical and mental health maintenance to eat such high-nutrition foods as are only available locally (not bred for distance shipping), from plants and animals that are well-nourished themselves.
This research write up is published at Journeytoforver.