Patients say keto helps with their mental illness. Science is racing to understand why

Iain Campbell, a researcher in Scotland, has lived with bipolar disorder since he was young. After trying the ketogenic diet, he discovered profound improvements in his symptoms — and now wants to learn if it can do the same for others. He shared his recent findings at the Metabolic Health Summit in Clearwater, Fla., on Jan. 25, 2024. (Tina Russell for NPR)

Iain Campbell was gazing out the bus window on his way to work when he first sensed something radical was reshaping how he experienced the world.

The inkling emerged from an altogether ordinary observation: He felt peaceful, maybe even happy as he watched the trees along the road pass by.