Thousands of people hoping to stay sharp as they age take Omega-3 fish oil supplements based on information from past studies, but new research is casting doubt on those claims. 

A review of past studies found that older people who took Omega-3 supplements did not score any better on thinking and memory tests than participants who took a placebo. 

"This is a great shame," said Dr. Alan Dangour, of the London School of Hygiene & Tropical Medicine. "It would be lovely to find a solution for cognitive decline and dementia, and unfortunately, the evidence as it stands says it does not benefit cognitive function in older people."

Other experts are standing by previous claims, saying the recent study wasn't long enough and that subjects in the study weren't old enough. 

"Those were young patients by any standards," said Dr. Gisele Wolf-Klein, the director of geriatric education at North Shore-LIJ Health System. "They were in the 60s or early 70s. Today that's middle age."

Until more research is completed, it will be up to each individual to decide whether Omega-3 supplements, which include fatty acids that are an important part of a healthy diet, are worth taking. 

Dorene Lebowitz, who has taken supplements for 10 years hoping to keep her mind sharp, said she's not giving them up. 

"I've heard and read more positive things about it, so I would continue it," she said. "It doesn't seem to have anything that could be harmful."

For people who do decide to stop taking the supplements, doctors still recommend eating two servings of fish a week. Mackerel, tuna, sardines, herring and trout are all fish that are high in Omega-3 fatty acids.