For people with the 'right' genetic background – those predisposed to developing MS because of a strong family genetic tendency to MS – certain environmental factors increase the risk of developing the disease. These factors include:
- Low levels of vitamin D while still in utero
- Low levels of sun exposure during childhood (particularly in winter and ages 6-15)
- High cow’s milk consumption as a child and adolescent
- High body-mass index during adolescence
- Smoking (including passive smoking)
- High saturated fat diet
Once a person has MS, only environmental factors affect the progression of the disease, not genetics. Note that one cannot 'catch' MS from a family member or anyone else.