diets aren't great in first world countries. hence the public health focus on correcting systemic problems that create huge economic burdens due to preventable chronic diseases.
multivitamins don't necessarily cut it - not all are created equal, and it depends what a person is eating in combination with said multi.
there are well researched deficiencies that are experienced by athletes. I can link you up to a long history of chats on that topic here at tims, if you are interested in the details. I've coached a personal friend through this exact situation as well. I have a copy of the bloodwork showing the problems manifesting from her outwardly healthy lifestyle. in the end it all came down to food choices (multi and all) paired with excess exertion.
lots of people would say they ate healthily growing up but that they have learned that what they thought was healthy was not necessarily balanced enough for good health.
many would suggest that the latitude piece is linked to vit D, which would tend to be low in everyone at northern latitudes, so why don't we all have ms closer to the poles? and why is japan an exception to the rule when it comes to ms in particular? because it's not just micronutrients, it's macronutrients, personal habits, combinations, ratios, genetics, all mixed up together.
and as for genetics - what about epigenetics? genetic expression is certainly influenced by nutrition.
on average, vegetarians and vegans have parallel nutrient issues to those seen in ms patients. I had amazing benefits with just a dumbed down easy version of the klenner protocol for ms. it hits on a bunch of different nutrients that are known to be subpar in ms patients (it misses vit D but that's because it's older)
as for the saturated fat idea, that is probably a thing for some ms patients, but certainly not all. i ended up with an ms dx in spite of no saturated fat or red meat in my diet whatsoever. as a vegan I certainly would have had insufficient protein and a crap omega 6 to omega 3 fatty acid ratio.
dietary protein is a good tie in to enzymes...
enzymes bring us back to diet and nutrition again.. where exactly do enzymes come from, and how are we able to use them (or not)?
I could go on in detail with supporting research ad nauseum, but I have some academic deadlines to worry about and shouldn't really be here at all today