Previous studies have reported that methionine, an amino acid, may raise levels of homocysteine, a compound that is considered a risk factor for inflammation. Domenico Pratico, from Temple University (Pennsylvania, USA), and colleagues have previously demonstrated that a diet rich in methionine could increase the risk of developing Alzheimer's Disease (AD).  In new research, the team fed one group of mice a diet high in methionine and another group a regular, healthy diet. After five months, they split the group receiving the methionine-rich diet into two, with one group continuing the amino-heavy diet while the second switched to the healthy diet for an additional two months. At the conclusion of the study, the researchers found that the dietary switch reversed the cognitive impairment caused by the methionine-rich diet, as measured by fewer amyloid plaques in the animals’ brains.  In addition, the team reports that the cognitive impairment that had been observed in the mice after three months on the methionine-rich diet was completely reversed after two months on the healthier diet, and they were now able to function normally.  Writing that: “Our results demonstrate that lowering [elevated homocysteine] … is beneficial since it significantly improves behavior deficits and brain amyloidosis,” the researchers conclude that: “Our findings provide new biological insights for future clinical trials aimed at lowering this modifiable risk factor in human [Alzheimer’s Disease].”