Mixed Message on Methionine

Methionine is an essential amino acid that is required for the absorption, transportation, and bioavailability of zinc and selenium in the body. Previously, some studies have reported that supplementary methionine may increase homocysteine levels – a known risk factor for cardiovascular disease,  Anuradha Kalani, from the University of Louisville (Kentucky, USA), and colleagues fed mice a diet containing high amounts of methionine and low amounts of folate and vitamins B6 and B12. They measured the mice's memory capability along with netrin – protein important for maintaining the brain, and brain levels of methylation – a process that causes excessive silencing of genes. The team observed that the longer the mice were on the diet, the less netrin was expressed and the more the netrin gene was methylated , and the investigators submit that a high-methionine diet induces learning and memory defects and that memory loss may be associated with reduced levels of netrin because of its over-methylation.  The study authors report that: " Our findings suggest that an excess methionine diet caused memory impairment and hyper-methylation that affected netrin expression, which is a protein important in maintaining synaptic plasticity and involved in axonal guidance and neurogenesis.”