The headaches would usually come on gradually and then build, causing excruciating pain and pressure behind her left eye that would culminate in her vomiting or visiting the emergency room. The ordeal would often leave her feeling weak and exhausted for days afterward.

“Anytime I had a migraine I’d be wiped out for three or four days,” said Ms. Kamka, 58, a post office clerk who lives near Fort Bragg, N.C. “I missed a lot of work because of migraines.”

But a few years ago, Ms. Kamka and 181 other people who routinely experience migraine headaches joined a clinical trial, sponsored by the National Institutes of Health, which was designed to test whether a special diet could alleviate their frequent headaches. The diet that Ms. Kamka was assigned to follow emphasized foods that contain large amounts of omega-3 fatty acids, the oils found in some fish, while limiting foods that are rich sources of omega-6 fatty acids, such as many vegetable oils.

Omega-3s and omega-6s are both considered essential fatty acids — critical for health, and because our bodies can’t make them, they must be obtained from foods. Historically humans consumed roughly equivalent amounts of both fatty acids. But the typical American diet today tends to contain a much larger proportion of omega-6 fats. Some health authorities see this as a good thing: Vegetable oils and other rich sources of omega-6 fats have been found in many studies to be beneficial for cardiovascular health. But others argue that this could be problematic because omega-6 fats have been shown to promote pain and inflammation, while omega-3 fats tend to have the opposite effect in studies, helping to reduce pain and inflammation.

The authors of the new study wanted to know: Could a diet that boosts omega-3 fats while lowering omega-6 fats make life easier for people burdened by frequent migraine headaches?

For Ms. Kamka, the benefits of a change in diet were striking: After a few months of increasing her fish intake and avoiding many common vegetable oils, she noticed that her headaches had all but disappeared. Other people on the new diet also reported fewer headaches. Although the trial ended after 16 weeks, Ms. Kamka has remained on it ever since. Gone are the days when she ate foods like fried chicken, French fries and potato chips that were cooked in vegetables oils rich in omega-6 fats. She now makes a point of eating foods like cod, tuna, sardines, spinach salads, hummus and avocados, and she cooks with olive oil instead of corn, soybean and canola oils.