VITAMIN-D AND MULTIPLE-SCLEROSIS

Recently, it has been clearly demonstrated that exogenous 1,25-dihydro xyvitamin D-3, the hormonal form of vitamin D-3, can completely preven t experimental autoimmune encephalomyelitis (EAE), a widely accepted m ouse model of human multiple sclerosis (MS). This finding has focused attention on the possible relationship of this disease to vitamin D. A lthough genetic traits certainly contribute to MS susceptibility, an e nvironmental factor is also clearly involved. It is our hypothesis tha t one crucial environmental factor is the degree of sunlight exposure catalyzing the production of vitamin D-3 in skin, and, further, that t he hormonal form of vitamin D-3 is a selective immune system regulator inhibiting this autoimmune disease. Thus, under low-sunlight conditio ns, insufficient vitamin D-3 is produced, limiting production of 1,25- dihydroxyvitamin D-3, providing a risk for MS. Although the evidence t hat vitamin D-3 is a protective environmental factor against MS is cir cumstantial, it is compelling. This theory can explain the striking ge ographic distribution of MS, which is nearly zero in equatorial region s and increases dramatically with latitude in both hemispheres. It can also explain two peculiar geographic anomalies, one in Switzerland wi th high MS rates at low altitudes and low MS rates at high altitudes, and one in Norway with a high MS prevalence inland and a lower MS prev alence along the coast. Ultraviolet (UV) light intensity is higher at high attitudes, resulting in a greater vitamin D-3 synthetic rate, the reby accounting for tow MS rates at higher altitudes. On the Norwegian coast, fish is consumed at high rates and fish oils are rich in vitam in D-3. Further, experimental work on EAE provides strong support for the importance of vitamin D-3 in reducing the risk and susceptibility for MS. If this hypothesis is correct, then 1,25-dihydroxyvitamin D-3 or its analogs may have great therapeutic potential in patients with M S. More importantly, current research together with data from migratio n studies opens the possibility that MS may be preventable in genetica lly susceptible individuals with early intervention strategies that pr ovide adequate levels of hormonally active 1,25-dihydroxyvitamin D-3 o r its analogs.