A new study has found that persons with Laron Syndrome (a kind of dwarfism) get almost no acne. Persons with this syndrome, because of a mutation, are insensitive to growth hormone. As a result, they produce much less IGF-1 (insulin-like growth factor) than normal. When given synthetic IGF, they may develop acne; when the dose is reduced, the acne goes away. The authors say: “The findings suggest that an interaction between IGF-1 and androgens is necessary for the development of acne.” This is great progress because people with Laron Syndrome are different from everyone else in just one tiny way (albeit a tiny way with many consequences).
The first important step in understanding the cause of acne was finding two (“primitive”) groups of people with no acne. This suggested that acne has an environmental cause. There were thousands of differences between the lifestyle of those people and “modern” people, so this was just a start. It was hard to know which differences mattered. The Laron Syndrome finding is consistent with the earlier result (no acne in two groups of “primitive” people) because a “Western diet with [its] high intake of hyperglycemic carbohydrates and insulinotropic dairy over-stimulates IIS” (insulin-like/insulin signaling).
This view predicts that if you replace hyperglycemic foods with foods lower in glycemic index acne should be reduced. This study did that and, indeed, acne decreased (compared to a control group) after ten weeks. The study ended after ten weeks. The patient who reduced his/her glycemic index the most saw the greatest decrease in acne. A second study found the same thing: a low-glycemic-index diet reduced acne. It lasted twelve weeks. With longer follow-up, there might have been even more improvement.
Thanks to Paul Nash.