Another study links sunshine, vitamin D and multiple sclerosis risk

In February I wrote about low vitamin D levels and the risk of relapse in multiple sclerosis patients, I also mentioned a study which linked season of birth to risk for the development of multiple sclerosis.  A study recently published in the British Medical Journal (1) indicates that sunlight exposure, possibly linking to vitamin D, during pregnancy might impact the risk of multiple sclerosis in the child.

Multiple sclerosis is the most common disabling neurological condition affecting young adults. Around 100,000 people in the UK have multiple sclerosis.  For more information about the condition please visit the MS society website.  The MS Society is the UK’s largest charity for people affected by multiple sclerosis.  Multiple sclerosis is the result of damage to myelin, a protective sheath surrounding nerve fibres of the central nervous system.  When myelin is damaged, this interferes with messages between the brain and other parts of the body.  Multiple sclerosis, often called MS, is categorised as a type of autoimmune disorder where the body’s own defence system breaks down the protective myelin around nerve fibres. 

This recent Australian study (1) found that children whose mothers had low sunlight exposure during their first three months of pregnancy might have a higher risk of developing multiple sclerosis later in life.  The authors of the study postulate that the risk is linked to low vitamin D levels which have previously been linked to a higher risk of MS development.  It is thought that low vitamin D, due to lack of sunlight exposure, might be having an effect on the developing foetus’s immune system or central nervous system and hence increasing the risk of it developing MS later in life.  There was about a 30% higher risk of multiple sclerosis in those who were born in the early summer months when their mothers would have had lower sunlight exposure during early pregnancy (the first trimester). 

Higher exposure to ultraviolet radiation (sunlight), higher vitamin D intake, and also higher serum vitamin D concentrations seem to be associated with a reduced risk of onset of multiple sclerosis. This evidence comes from various studies and indicates that age of operation for such a protective effect might include both childhood and early adulthood.  Pregnancy is a vulnerable time for vitamin D deficiency because of increased physiological needs and reduced maternal outdoor activity.  Although human evidence pertaining to foetal development has been difficult to obtain, the body of related evidence to date has led some to recommend antenatal supplementation with vitamin D to prevent multiple sclerosis(1).

Vitamin D may be particularly important for the development of the foetus’s central nervous system.  The authors write (1)Vitamin D supplementation for the prevention of multiple sclerosis might also need to be considered during in utero development“.  The findings are supported by previous studies which also found more cases of MS among people whose mothers probably had little exposure to sunlight in their first trimester of pregnancy.  The researchers of this study conclude “Region of birth and low maternal exposure to ultraviolet radiation in the first trimester are independently associated with subsequent risk of multiple sclerosis in offspring in Australia(1).

The study is important and interesting but ultimately it is only an association study and does not directly examine vitamin D status of foetus or mother.  Further work is necessary to look deeper at the associations and the potential for vitamin D supplementation in pregnancy and beyond.  The authors of this study (1) do write about the potential use of vitamin D supplementation in pregnancy, childhood and adolescence as a means of preventing auto-immune diseases including multiple sclerosis and I look forward to seeing further work in this area.

Vitamin D has been heavily researched over the last 3 years and exciting results have been found with regards many conditions from cancer to heart disease, for more information please visit my past posts on Vitamin D.  Recently I also wrote about a group of researchers who recommend vitamin D supplementation in pregnancy, to read this piece pleace click here.  What is known, as mentioned in my previous posts, is that many people in the UK do not get enough vitamin D and have insufficient/deficient blood levels.  There is no current consensus about the amount of daily vitamin D intake necessary to maintain blood levels at around 40-50nmol/l (which is currently seen as optimal by many medical practitioners).  There is some suggestion that most adult (age 18 and over) individuals in the UK would require a supplement of around 2000iu vitamin D daily.  Higher doses (up to 5000iu daily) may well be useful but I would not recommend such a regimen unless under the supervision of a medical doctor who can monitor blood levels regularly.  Pregnant women should not take any nutritional supplements without checking with their GP and/or midwife first.

 

(1) Judith Staples J et al.  2010.  Low maternal exposure to ultraviolet radiation in pregnancy, month of birth, and risk of multiple sclerosis in offspring: longitudinal analysis.  BMJ.  340:c1640  doi:10.1136/bmj.c1640

Written by Ani Kowal

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