Metformin has been prescribed for more than sixty years, and nobody can agree on how it works. The liver was the standard answer. Then the gut made a strong case. Last year, a team at Baylor College of Medicine added a third candidate that got the most attention of the three, because it was the least expected: the brain.
The finding is real, and the experiments are careful. But it carries a complication that most coverage skipped past, and it is not a small one. Metformin is a positively charged, water-loving molecule that does not readily cross into the brain, and the experiments that most directly implicate the brain delivered the drug straight into the ventricles, bypassing the barrier entirely.
