Vitamin D and Multiple Sclerosis: Separating Evidence from Expectation

But if we think about epidemiological evidence to start with, what has that told us about the relationship between vitamin D and the risk of developing MS? Debbie, maybe I'll start with you.

Okay, just like to say that I'm very much a clinical person.

I don't do a lot of lab stuff.

And so I come to this question quite a lot from a sort of a clinical approach.

I think one of the things that it's really important to recognize is the role of vitamin D in a person in developing MS and as opposed to its role as a disease-modifying treatment.

And one of the things I think that has been sort of confusing in this space is that Some of the work is around people who already have MS or at very high risk of MS probably do have MS, as opposed to the factors that may make people at risk of developing the disease compared to somebody who doesn't develop MS.

And I think that that's important.

There's no doubt that vitamin D deficiency is important a factor in developing MS, that sufficiency is important and protective for MS.

And the factors that sort of decide whether a person develops or is vitamin D sufficient is things like latitude, environmental factors, dietary factors, genetic factors, probably UVB exposure.

And also from our research, we've come across the fact that timing is also very important.

So we did the prevalence study 2006, and we identified every person in New Zealand with multiple sclerosis on Census Day.

And the two things that we found very striking in that was, one, we have a very robust latitude gradient between our northern people and our southern people, which is a three-fold difference across a relatively small latitude.

But we also did diaries on every person from the time that they were born to when they developed MS.

And we found that actually that latitude gradient was most profound actually in their early years, long before they were diagnosed.

And the gradient at about the age of 12 started to drop.

So I think this gives us an idea that there may be factors involved in the development and very early that actually make our risk high.

Then, of course, there's a whole lot of factors around whether if you are going to get MS or if you've got MS, whether vitamin D supplementation changes the course of the disease itself.

Yes, of course.

I think it's very interesting because, yes, indeed, the risk of MS has been confirmed in relationship with the vitamin D deficiency, but maybe there are more profound reasons for that.

The nutrition is important, of course, but the genetics brings maybe some causality link with the Mendelian studies that have shown that If you think about the levels of vitamin D determined by your genetic profile, it is related to the risk of MS, suggesting that low vitamin D is causal in MS.

And that's some very important research results.

And also another comment on what you said is about UV exposure.

It seems that UV exposure has a relationship, of course, with the circulating vitamin D levels, but it might also have some intrinsic pathways and action on the immune system that are different from those of vitamin D.

They are connected, of course, but they might bring some complementary effects on the risk of MS. Diaries in childhood and adolescence are very useful and indeed showed that the risk is at a certain period of the development of the people, especially when the immune system is maturing and during childhood and adolescence.

So these are for me the key facts that must be kept in mind about this relationship between the risk of MS and vitamin D deficiency.