Vitamin D Intake and Incidence of Multiple Sclerosis
Vitamin D intake and incidence of multiple sclerosis NEUROLOGY, January 13, 2004;62:60-65
K. L. Munger, MSc, S. M. Zhang, MD ScD, E. O'Reilly, MSc, M. A. Hernán, MD DrPH, M. J. Olek, DO, W. C. Willett, MD DrPH and A. Ascherio, MD DrPH
A protective effect of vitamin D on risk of multiple sclerosis (MS) has been proposed, but no prospective studies have addressed this hypothesis.
Dietary vitamin D intake was examined directly in relation to risk of MS in two large cohorts of women: the Nurses' Health Study (NHS; 92,253 women followed from 1980 to 2000) and Nurses' Health Study II (NHS II; 95,310 women followed from 1991 to 2001). Diet was assessed at baseline and updated every 4 years thereafter.
The pooled age-adjusted relative risk comparing women in the highest quintile of total vitamin D intake at baseline with those in the lowest was 0.67 [This means that those with the greatest vitamin D has a 33% reduced risk of developing MS].
Intake of vitamin D from supplements was also inversely associated with risk of MS; the relative risk comparing women with intake of >or=400 IU/day with women with no supplemental vitamin D intake was 0.59 [This means that those who supplemented with at least 400IU vitamin D per day had a 41% reduced risk of developing MS].
Intake of vitamin D from supplements was inversely associated with risk of MS.
No association was found between vitamin D from food and MS incidence.
These results support a protective effect of vitamin D intake on risk of developing MS.
THESE AUTHORS ALSO NOTE:
"The incidence of multiple sclerosis (MS) is low in the tropics and increases with distance from the equator in both hemispheres."
"One hypothesis is that sunlight exposure and the resulting increase in vitamin D may exert a protective effect."
"Vitamin D has strong immunoregulatory effects, and vitamin D supplementation prevents experimental autoimmune encephalo-myelitis (EAE), an autoimmune disease in animals that is used as a model of MS."
"Studies on vitamin D and MS have found that individuals with MS tend to have insufficient vitamin D levels and that periods of low vitamin D precede the occurrence of high lesion activity, whereas periods of high vitamin D precede low lesion activity, as detected by MRI."
These authors used the data from two large prospective cohorts to examine whether or not high vitamin D intake reduces the risk of MS.
This study analyzed two groups of nurses in the US, one having 92,253 women and the other having 95,310. They assessed vitamin D intake from food and supplements.
The food items that mostly contributed to vitamin D intake were skim/low-fat milk and fish.
Use of vitamin D supplements was collected. Analyses were conducted to examine the separate effects of vitamin D from foods or from supplements.
"Total vitamin D intake was inversely associated with risk of MS."
The authors "found no associations between vitamin D intake from food only and risk of MS." [Very Interesting]
"Vitamin D intake may be more important for women living in regions at high latitude where winter sunlight is insufficient."
The duration of use of multivitamins with vitamin D further reduced MS risk, with a 59% reduction of risk if using these supplements for more than 10 years.
"In this large prospective study, we found that women who used supplemental vitamin D, largely from multivitamins, had a 40% lower risk of MS than women who did not use vitamin D supplements."
"A protective role of vitamin D has been proposed to explain the well-known latitude gradient in MS incidence and prevalence."
The positive effects of vitamin D may be related to its ability to inhibit the production of proinflammatory cytokines.
Vitamin D can also lower the risk of type 1 diabetes if supplemented in the first year of life.
These authors note that the protection against MS may be due to other components of multivitamins, such as vitamin E, folic acid, zinc, and vitamins B1, B2, B6, and B12. [Important] However, previous studies found no associations between the use of multivitamin supplements and risk of MS. "Therefore, a protective effect of vitamin D seems a more likely explanation of the observed associations."
These authors found "a 40% reduction in risk of MS among women who use supplemental vitamin D, primarily in the form of multivitamins, compared with women who do not use supplements."
KEY POINTS FROM DR. DAN MURPHY
1) The incidence of multiple sclerosis (MS) is low in the tropics and increases with distance from the equator in both hemispheres. Sunlight exposure and the resulting increase in vitamin D may exert a protective effect against MS.
2) Vitamin D intake may be more important for women living in regions at high latitude where winter sunlight is insufficient.
3) Individuals with MS tend to have insufficient vitamin D levels.
4) Periods of low vitamin D precede the occurrence of high MS lesion activity, and periods of high vitamin D precede low MS lesion activity, as detected by MRI.
5) This study found that women who used supplemental vitamin D had a 40% lower risk of MS than women who did not use vitamin D supplements.
6) Taking vitamin D supplements for more than 10 years lowered the risk of developing MS by 59%.
7) There was no reduced risk of MS with increased vitamin D intake from food. It had to be in the form of supplements.
8) Vitamin D supplements in the first year of life, reduces the risk of type-1 diabetes.
9) Vitamin D has strong immunoregulatory effects.
10) These results support a protective effect of vitamin D supplement intake on risk of developing MS. [Recent studies are advocating that we all supplement with 1000 IU of vitamin D per day.]