I often focus on the bigger facets of the disease of civilization. Things like cardiovascular disease and cancer, which are major killers and the subject of intensive research. But the disease of civilization is a spectrum of disorders that affects the body in countless ways, large and small.
I recently read an interesting paper written by an all-star cast, including Loren Cordain, Staffan Lindeberg and Boyd Eaton. It's titled "Acne Vulgaris: A Disease of Western Civilization". The paper presents data from two different groups, the Kitavans of Papua New Guinea and the Ache hunter-gatherers of Paraguay. Both were systematically examined by doctors trained to diagnose acne. Out of 1,200 Kitavans and 115 Ache of all ages, not a single case of acne was observed. Hunter-gatherers and other healthy non-industrial cultures have nice skin. I dare you to find a pimple in Nutrition and Physical Degeneration.
In Western societies, acne is a fact of life. The paper states that 79 to 95% of modern adolescents suffer from some degree of acne, along with about 50% of young adults. That's an enormous difference.
The paper presents a very Cordain-esque hypothesis to explain the high incidence of acne in Western societies. In sum, they state that the Western diet causes hyperinsulinemia, which is thought to promote acne. This is due to insulin's effects on skin cell proliferation, its interference with the retinoid (vitamin A) signaling pathway, and its effect on sebum production.
They then proceed to point the finger at the glycemic index/load of the Western diet as the culprit behind hyperinsulinemia. It's an unsatisfying explanation because the Kitavans eat a diet that has a high glycemic load due to its high carbohydrate content, low fat content, and relatively high-glycemic index foods. I think the answer is more likely to reside in the specific types of carbohydrate (processed wheat) rather than their speed of digestion, with possible contributions from refined vegetable oil and an excessive sugar intake.