hi there, well at this stage in my thinking process, i think it's a combination of genetics and environment. and i'm not just talking about ms but any chronic illness.
more specifically, i think of disease as a combination of genetic predisposition and environment (environment being the nutrient/toxin/stress conditions experienced by a human being from its earliest conception, with the nutrient status of the parents influencing initial genetic composition, and the body of the mother providing a more or less nuturing landscape/ecosystem within which the fetus develops).
resulting humans are delivered from that ecosystem with more or less structural and functional capacity for health, and are born with a smaller or larger stockpile of the raw materials for keeping that system functional.
in some cases the initial 'account' might be great, at least sufficient to protect an individual from his or her inherited genetic frailties, and the patient might life life such that stocks are not depleted, and stay healthy longer.
in other cases stocks may be initially poor, and through life the individual might have to deal with structural or cognitive birth defects, experience more illness, be at higher risk for genetic expression leading to disease, and might have to work within limitations to build up the raw materials for maintaining a system in the best possible way.
in yet other scenarios, a patient might start out with poor status, then experience an emotionally, physically or nutritionally toxic environment early in life, or make poor lifestyle choices later on, and end up sickest of all. just thinking out loud
i agree with you that diets are not necessarily the best solution, especially diets without science. anyway i'm sidetracked from some important business day errands right now, so will be back later