And in a study published last year, researchers in Australia showed in a double-blind, placebo-controlled trial that subjects with suspected gluten sensitivity had substantially fewer symptoms on a gluten-free diet than control subjects who unknowingly ingested gluten.

WSJ: New Guide to Who Really Shouldn't Eat Gluten

E, the second another (as yet unannounced) compound suspected of having anti-Alzheimer's properties, and the third an inert placebo as a control.

ECONOMIST: Disposing of dementia

One such, carried out in the British city of Durham, was controversial in that it was funded by a maker of children's omega-3 supplements and did not include a control group being given a placebo.

ECONOMIST: Eat your way to a better brain

In the double-blind, randomized control trial, half the women got tenofovir gel and half got a placebo.

CNN: Gel cuts HIV transmission rate in study