Pro-inflammatory immune cells play a pivotal role in multiple sclerosis, and the gut microbiota is increasingly recognized as a key factor shaping the immune system. This study aims to determine the impact of a dietary intervention (methionine-restricted diet-MR) on gut microbiota and inflammation in humans. A randomized interventional pilot study with cross-over intervention is conducted in 40 healthy participants. For all participants, the first two weeks (week 1+week 2) consist of baseline assessment on their usual diet, and week 3+week 4 consist of MR diet only. For group A, the week 5+week 6 are MR+1,500 mg daily supplementation of methionine and for group B are MR+placebo, with a cross-over for week 7+week 8. Usual diet is resumed for all participants during week 9+week 10. Gut microbiota, blood levels of methionine and its metabolites, as well as immune and inflammatory markers will be evaluated every 2 weeks. It is hypothesized that MR could be used in humans to prevent and alleviate the course of multiple sclerosis by shaping the gut microbiota towards an anti-inflammatory profile, and that the gut microbiota is a biomarker associated with successful dietary interventions targeting inflammation in multiple sclerosis.