A healthy diet, crossword puzzles and regular exercise may help the brain, but there isn't enough evidence they delay or reduce the severity of Alzheimer's disease, a panel of experts in the U.S. says.

An independent panel of 15 experts in geriatrics, neurology, psychiatry, human nutrition, nursing and other fields was convened by the U.S. National Institutes of Health to assess the latest evidence on preventive measures for Alzheimer's.

"We wish we could tell people that taking a pill or doing a puzzle every day would prevent this terrible disease, but current evidence doesn't support this," said Dr. Martha Daviglus, conference panel chair and professor of preventive medicine and medicine at Northwestern University in Chicago.

While there is little evidence such measures lessen cognitive decline, some are not necessarily harmful and may offer other benefits.

The panel, however, said the public needs to understand such strategies are at best only loosely associated with an improved outcome.

The cause-and-effect relationship, if any, is unclear, Daviglus said.

"Are people able to stay mentally sharp over time because they are physically active and socially engaged, or are they simply more likely to stay physically active and socially engaged because they are mentally sharp?"

In Wednesday's report, the panellists also made recommendations on research to fill in gaps in understanding of cognitive decline and Alzheimer's. They hope to create registries for Alzheimer's to learn more about the history and progression of the disease.

Amyloid plaques are found in the brains of people with the disease, but it is unclear whether the plaques cause Alzheimer's or are a symptom of it.

Alzheimer's is the most common form of dementia and affects one in 20 Canadians over 65 — about 290,000 people.