The study, published in the American Journal of Geriatric Psychiatry, involved 40 adults who had mild memory complaints.
Eating turmeric daily may boost your memory and uplift your mood, a study suggests.
Found in turmeric, curcumin has previously been shown to have anti-inflammatory and antioxidant properties.
It also has been suggested as a possible reason that senior citizens in India, where curcumin is a dietary staple, have a lower prevalence of Alzheimer's disease and better cognitive performance.
"Exactly how curcumin exerts its effects is not certain, but it may be due to its ability to reduce brain inflammation, which has been linked to both Alzheimer's disease and major depression," said Gary Small, from the University of California, Los Angeles in the US.
The study, published in the American Journal of Geriatric Psychiatry, involved 40 adults between the ages of 50 and 90 years who had mild memory complaints.
They were randomly assigned to receive either a placebo or 90 milligrammes of curcumin twice daily for 18 months.
All 40 subjects received standardised cognitive assessments at the start of the study and at six-month intervals, and monitoring of curcumin levels in their blood at the start of the study and after 18 months.
Thirty of the volunteers underwent positron emission tomography, or PET scans, to determine the levels of amyloid and tau in their brains at the start of the study and after 18 months.
The people who took curcumin experienced significant improvements in their memory and attention abilities, while the subjects who received placebo did not, Small said.
In memory tests, the people taking curcumin improved by 28 per cent over the 18 months.
Those taking curcumin also had mild improvements in mood, and their brain PET scans showed significantly less amyloid and tau signals in the amygdala and hypothalamus than those who took placebos.
The amygdala and hypothalamus are regions of the brain that control several memory and emotional functions.
Four people taking curcumin, and two taking placebos, experienced mild side effects such as abdominal pain and nausea, the researchers said.
"These results suggest that taking this relatively safe form of curcumin could provide meaningful cognitive benefits over the years," said Small.