Nutrition and Physical Degeneration - Weston Price
I think everyone alive should read this book.
This is one of the most important historical texts about natural nutrition. Long before the age of supplements, Price showed that nutritional deficiencies caused by processed foods destroyed the health of "primitive" populations.
Price documented exactly how healthy people were compromised by modern foods, particularly processed flour and sugar. His work will probably never be replicated because uncontacted populations are extremely rare now. He showed up at the perfect time where several well-established populations were changing their food sources.
Understanding how primitive populations were able to remain healthy is an excellent comparison to modern government-funded healthcare.