Scientists believe that eating a Mediterranean diet may reduce the chances of needing Alzheimer's disease care.
The diet has been widely recommended in recent years following a flurry of studies showing its benefits for health.
Followers eat plenty of fruit, vegetables, fish, olive oil and dairy, while avoiding too much red meat and saturated fat.
The latest research, which appears in the Archives of Neurology, suggests that people who eat a Mediterranean diet are less likely to develop mild cognitive impairment, while those who already have mild cognitive impairment can reduce their risk of developing Alzheimer's disease.
The researchers, who are based at Columbia University Medical Centre, wrote: "Potentially beneficial effects for mild cognitive impairment or mild cognitive impairment conversion to Alzheimer's disease have been reported for alcohol, fish, polyunsaturated fatty acids (also for age-related cognitive decline) and lower levels of saturated fatty acids."
Rebecca Wood, chief executive of the Alzheimer's Research Trust, commented: "Diet almost certainly plays a part in every person's Alzheimer's risk - and diet remains a magnet for research because it could offer a relatively inexpensive way to fight a disease that ruins countless lives."