Taking certain supplements may not reduce the risk of memory and thinking problems, according to the largest study to date on the connection.

In the study published in Neurology, researchers focused on homocysteine, an amino acid. High levels of homocysteine have previously been linked with memory loss and Alzheimer’s disease.

"Since homocysteine levels can be lowered with folic acid and vitamin B12 supplements, the hope has been that taking these vitamins could also reduce the risk of memory loss and Alzheimer's disease," study author Rosalie Dhonukshe-Rutten, of Wageningen University in Wageningen, the Netherlands, said in a news release.

Dutch researchers studied 2,919 people who had high blood levels of homocysteine. For two years participants, who had an average age of 74, took either a daily tablet with 400 micrograms of folic acid and 500 micrograms of vitamin B12 or a placebo.

Researchers administered memory and thinking skill tests at the beginning and end of the study.

At the end of the study they found that homocysteine levels decreased by more in the supplement group, but there was no difference in scores on the thinking and memory tests.

Previous observational studies showed there may be a benefit to taking folic acid and vitamin B12 for memory, but later randomized , controlled trials were less definitive.