We have known for over 60yrs of the association of lack of sun exposure (marker for low vitamin d status) and MS incidence.
Only those determined to put themselves at increased risk of MS, DIABETES, Alzheimer's, Cancer, Heart Disease, Depression, and virtually every condition that involved inflammation and/or infection will choose to continue to remain vitamin d deficient.
Only health professionals who put their own financial wellbeing above the best health interests of their patients will continue not to test 25(OH)D levels and continue to use Vitamin D2 in place of the natural human form D3
Rather than call for further research, the presumption should be that the natural 25(OH)D pale skinned human bodies naturally attain and maintain given regular full body non burning sun exposure and at which human milk is a Vitamin D3 complete food for human babies, should be the standard.
We should not adopt the definition of deficient or insufficient status as the lowest those with a vested financial interest in profiting from treating vitamin d related conditions can get away with.
We should also bear in mind that preventing a condition is different from treating a condition.
Those with MS (or any other vitamin d related condition) still need to correct vitamin d deficiency/insufficiency (by my definition that means keeping everyone in the 50~70ng/ml ranges and involves regular 25(OH)D testing until you are confident you understand the daily sun/uvb/supplement combination your body requires) but they shouldn't expect that closing the stable door after the horse has bolted will return the horse to the stable.
For those on the way to Alzheimer's we may know that low vitamin d3 levels are associated with mild cognitive impairment (precusor condition for AD) correcting vitamin d3 (and melatonin) levels can only slow the progression at that point and will not repair all the damage caused by being vitamin d deficient for the 20~30 preceding years over which the damage has progressively built up.
But with both MS/ALZHEIMER'S we know sufficient about the genes involved to appreciate that these genes are only switched on when the deficiency exists. So maintaining an adequate vitamin d3 melatonin level throughout life keeps those with the genetic potentiality for MS AD Diabetes etc safe.
We SHOULD NOT be calling for more research BEFORE we correct vitamin D deficiency. We should put common sense and personal health before the financial well-being of of the corrupt drugs industry and greedy health professionals.