Have you ever considered undergoing brain-thickening surgery, only to find that such a thing does not exist? And that the guy in the van was probably not actually a surgeon? Well, consider fish.

Dr. Cyrus Raji, a resident radiologist at UCLA, appreciates value beyond the cosmetics of a thick cerebral cortex. He's the lead researcher in a new study in the current American Journal of Preventive Medicine that found that people who regularly eat fish have more voluminous brains than those who do not—in such a way that stands to protect them from Alzheimer's disease.

"Understanding the effects of fish consumption on brain structure is critical for the determination of modifiable factors that can decrease the risk of cognitive deficits and dementia," Raji and colleagues write. The team has previously shown gainful effects of physical activity and obesity on brain structure.

This study found that eating fish—baked or broiled, never fried—is associated with larger gray matter volumes in brain areas responsible for memory and cognition in healthy elderly people.

"There wasn't one type of fish that was the best," Raji told me by phone, probably while eating fish. "All that mattered was the method of preparation." Fried fish had a unique dearth of benefits to the brain.

"If you eat fish just once a week, your hippocampus—the big memory and learning center—is 14 percent larger than in people who don't eat fish that frequently. 14 percent. That has implications for reducing Alzheimer's risk," Raji said. "If you have a stronger hippocampus, your risk of Alzheimer's is going to go down."