Australian study finds multiple sclerosis risk 30% higher in kids whose first trimester occured during winter months: scientists suspect mothers' consequent lack of vitamin D
by Craig Weatherby
Multiple sclerosis (MS) is a disease in which the fatty myelin sheaths around the nerve fibers of the brain and spinal cord are attacked by the body’s immune system.
The damage caused by this “autoimmune” response to the body’s own nerves leads to a wide range of symptoms, including weakness, loss of vision, tremors, unsteadiness, and often, permanent disability.
The disease usually strikes adults in their 30's but MS can afflict children, and it is more common in girls and women than in males.
Importantly, MS is more common in countries that lie further from the equator, which get less sun, in terms of both the amount and strength of the UV rays that create vitamin D in the skin. But genetics must also play a role, because ethnic groups within the same region can have very different MS rates.
And growing research suggests that a consequent lack of vitamin D explains the link between getting less sun and being at higher risk for MS.
Like MS, childhood (type I) diabetes is an autoimmune disease, and previous research found that young children who took vitamin D pills were 29 percent less likely to develop childhood (type I) diabetes (See “Vitamin D May Deter Childhood Diabetes).
Now, a population study from Australia bolsters the idea that lack of vitamin D either causes MS directly, or promotes it in people who are genetically predisposed to developing the disease (Staples J et al. 2010).
Researchers examined the birth records of 1,524 MS patients born between 1920 and 1950, and found that more were born in November or December.
Since Australia is in the southern hemisphere, this means that their first trimester occurred during Australia’s winter months of April to June, when temperatures drop and expectant mothers may spend more time indoors.
In contrast, far fewer MS patients were born in May and June, and therefore spent their first trimesters in Australia’s warmer months of September to November, when mothers would be more likely to be outdoors.
“The risk of multiple sclerosis was around 30 percent higher for those born in the early summer [colder, darker] months of November and December compared to the months of May and June,” the researchers wrote in a statement.
Their findings resemble those of studies conducted in the northern hemisphere, which found more cases of MS among people whose first trimester during autumnal months.
Why would vitamin lack lead to MS... and what should be done?
It’s not clear why vitamin D in pregnancy may protect a developing fetus, but researchers suspect it may work in any of three ways related to prevention or amelioration of the autoimmune responses behind MS:
Induce healthy nerve growth.
Exerting a positive, protective effect on the developing immune system.
Reduce the inflammation response in mothers who suffer an infection, which can damage the fetal nervous system.
Earlier research by some members of the same scientific team also found that MS risk was associated with having a particular variation in the gene that affects vitamin D receptors (Dickinson JL et al. 2010).
The researchers noted that although Australian women live in a sunny climate, they mostly have indoor jobs and spend leisure time indoor on the weekends.
And they said that even in southern Australia, it takes 2 to 3 hours of sunlight exposure per week on your face, hands, and arms to get enough vitamin D.
The Canadian Pediatric Society recommends pregnant women in that country take up to 2000 IU vitamin D during winter months.
Despite ample evidence that this higher level is both safe and necessary, the recommended intake for American and Australian mothers remains at a mere 200 IU.
In 2008, the American Academy of Pediatrics (AAP) doubled the amount of vitamin D it recommends for infants, children, and adolescents, from 200 IU per day to 400 IU per day.
But most experts say that the minimum daily allowance from adolescence on—and probably much earlier—should be 1,000 to 2,000 IU per day (see “Kids’ Daily Vitamin D Allowance Doubled”).
As the investigators wrote, “Overall, epidemiological studies support a protective role for vitamin D in autoimmune disease, particularly in childhood and adolescence, and vitamin D supplementation in early adulthood effectively reduces the risk of multiple sclerosis; therefore, supplementation of adolescents and young adults could be effectively used for prevention.”
And they broadened their recommendation to include very young children: “The findings here provide the first population based evidence… to indicate that vitamin D supplementation for the prevention of multiple sclerosis might also need to be considered during in utero development” (Staples J et al. 2010).
Indeed, vitamin D supplements should be a routine part of pre-natal nutrition for mothers, and for children from infancy onward.
- Lewis S, Lucas RM, Halliday J, Ponsonby AL. Vitamin D deficiency and pregnancy: From preconception to birth. Mol Nutr Food Res. 2010 May 3. [Epub ahead of print]
- Dickinson JL, Perera DI, van der Mei AF, Ponsonby AL, Polanowski AM, Thomson RJ, Taylor BV, McKay JD, Stankovich J, Dwyer T. Past environmental sun exposure and risk of multiple sclerosis: a role for the Cdx-2 Vitamin D receptor variant in this interaction. Mult Scler. 2009 May;15(5):563-70. Epub 2009 Apr 21.
- Staples J, Ponsonby A, Lim L. Low maternal exposure to ultraviolet radiation in pregnancy, month of birth, and risk of multiple sclerosis in offspring: longitudinal analysis. BMJ 2010;340:c1640 Published 29 April 2010, doi:10.1136/bmj.c1640