Significantly reducing dietary levels of the amino acid methionine could slow onset and progression of multiple sclerosis in high-risk individuals, according to a new study.

While many cell types in the body produce methionine, the immune cells responsible for responding to threats like pathogens do not. Instead, the methionine that fuels these specialized cells, called T cells, must be ingested through food consumption. Although methionine is found in most foods, animal products such as meat and eggs contain particularly high levels.

During an immune response, T cells flood the affected area to help the body fend off pathogens. Van Andel Institute's Metabolic and Nutritional Programming group researchers found dietary methionine fuels this process by helping "reprogram" T cells to respond to the threat by more quickly replicating and differentiating into specialized subtypes. Some of these reprogrammed T cells cause inflammation, which is a normal part of an immune response but can cause damage if it lingers, such as the nerve damage that occurs in MS.

The researchers also found that significantly reducing methionine in the diets of mouse models of MS altered the reprogramming of T cells, limiting their ability to cause inflammation in the brain and spinal cord. The result was a delay in the disease's onset and slowed progression.

Researchers said that restricting methionine in the diet is essentially removing the fuel for this over-active inflammatory response without compromising the rest of the immune system.

The researchers caution the findings must be verified in humans before dietary guidelines can be developed. The team also plans to investigate whether new medications can be designed that target methionine metabolism.

The findings were published in Cell Metabolism.