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Mild cognitive impairment (MCI), an intermediate state between normal brain function and dementia, is considered to be a precursor to Alzheimer’s disease (AD). Previous studies have suggested that both folic acid and the omega−3 fat docosahexaenoic acid (DHA) may benefit cognitive function in patients with MCI. Although the mechanisms that cause dementia are not well understood, there may be links to increased amyloid-β (Aβ) levels. Although both DHA and folic acid have been shown to individually reduce Aβ levels in cell and animal studies, this hasn’t been thoroughly tested in humans.

The study

In a 6-month randomized controlled trial, 138 patients (>60 years of age) with MCI were randomized into four different intervention groups: folic acid (0.8 mg/day) + DHA (800 mg/day), folic acid alone (0.8 mg/ day), DHA alone (800 mg/ day), or a placebo. Cognitive function (as assessed by a battery of tests) and amyloid-β levels in the blood were measured at baseline and after the 6-month intervention. Cognitive function was also assessed at a 12-month follow-up (6 months postintervention) to determine whether any improvements in cognitive function caused by the intervention were maintained.

The results

Folic acid alone improved the full-scale intelligence quotient (FSIQ), arithmetic, and picture complement scores. In the DHA-alone group, the FSIQ and information, arithmetic, and digit span scores improved. Folic acid + DHA improved arithmetic and digital span scores. At the 12-month follow-up, most measures of cognitive function declined relative to those measured immediately postintervention. DHA lowered levels of the 40-amino-acid Aβ40 peptide (Aβ40), while folic acid + DHA reduced Aβ42 and Aβ40 levels more than DHA alone. These results indicate that 6 months of combined folic acid and DHA supplementation can improve cognitive function in older adults with MCI, but the improvements in cognition may not be maintained after stopping supplementation.

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This Study Summary was published on May 4, 2021.