In the 1970s, Danish researchers studying Inuit metabolism proposed that omega-3 fatty acids found in fish were protective. Those conclusions eventually led to the recommendation that Westerners eat more fish to help prevent heart disease and sent tens of millions scrambling for fish oil pills.

Today, at least 10 percent of Americans regularly take fish oil supplements. But recent trials have failed to confirm that the pills prevent heart attacks or stroke. And now the story has an intriguing new twist.

Rasmus Nielsen, a geneticist at the University of California, Berkeley, and an author of the new study, said that the discovery raised questions about whether omega-3 fats really were protective for everyone, despite decades of health advice. “The same diet may have different effects on different people,” he said.

Read the article “Unless You’re Inuit, Maybe Omega-3 Fatty Acids Don’t Help After All” on nytimes.com.