Does vitamin D have role in autism?

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Hippocrates aptly stated, All disease begins in gut."

Vitamin D deficiency has been described as rising to epidemic proportions; however, not everyone agrees. Kikewise, recommendations for what is “normal leves” as well as indications for vitamin D supplementation are controversial.

Vitamin D status in health and disease

Vitamin D deficiency has been implicated in causation of multiple diverse diseases including neuro-psychiatric disorders like schizophrenia.

• Evidence supports a role of suboptimal vitamin D levels in depression.
• Autism shares many of the in-utero risk factors with schizophrenia.

Vitamin D and risk of autism

Recently several investigators have implicated vitamin D deficiency in increasing risk for autism [Cannell JJ 2010; Glasser 2009; Currenti 2010; Dealberto MJ 2011].

However evidence is circumstantial and studies examining direct cause-effect linkage are lacking.

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How vitamin D could affect autism risk and manifestations

1. Body does not wish to express all the genes present in the body all the time. Vitamin D plays an important role in gene regulation and its deficiency could initiate or expose the underlying genetic risk or induce genetic mutations.
2. Vitamin D plays an important role in DNA repair and its deficiency could impair reparative processes and increase risk for mutations.
3. Vitamin D has been shown to be neuroprotective. A deficient vitamin D state would increase the risk of brain injury during otherwise easier to manage acute problems during pregnancy like infections etc. or obstetric complications during delivery.
4. Vitamin D receptors are present in the central nervous system. Vitamin D deficiency would affect neurosignaling by its effects on neurotransmitters.
5. Vitamin D affects brain development via its neurotrophic effects. A deficiency would affect development of some or all parts of brain.
6. Calcitriol (the active vitamin D hormone) affects numerous neurotransmitters and neurotrophic factors, relevant for mental disorders.
7. Vitamin D enhances immune system and reduces viral infections. Vitamin D protects against Influenza which has been shown to damage brain. Putting these two together suggests that vitamin D may protect against infection and consequently reduce risk of harmful effects on brain.

Autism and vitamin D levels

Low levels of vitamin D have been documented in children with autism [Meguid 2010] as well as with other psychiatric problems including depression as compared to controls [Humble MB 2010]. A recent article in Mayo Clinic Proceedings (2011)documented correlation between  low vitamin D levels and depressive symptoms.

• In contrast, some studies have reported no difference in maternal vitamin D levels.
• The studies showing lack of relationship have been criticized for being too small to detect differences and for not examining prenatal levels or testing during pregnancy.

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Epidemiology of autism and vitamin D deficiency

Some data suggests vitamin D deficiency as a risk factor

• Parallel with increase in autism over the last few decades has been an increasing emphasis on protecting skin from sun’s ultraviolet rays thus reducing vitamin D synthesis and  causing increasing risk for vitamin D deficiency
• Children of mothers from outside Europe, America and Australia are at a greater risk for autism [Dealberto] and authors hypothesised  potentially lower vitamin D levels as potentially a causative factor.
• Others have argued that such ethnic/immigrant differences involve increased risk of allergic and autoimmune disorders and increased prevalence of autism may be immune dysfunction rather than vitamin D levels [Goines 2007].
• In contrast, another study comparing vitamin D levels found that the autism rates and vitamin D levels were similar in immigrant mother of kids with and without autism [Furnell 2010].
• There is no effect of paternal ethnicity.

Is It Leaky Gut or Leaky Gut Syndrome?

Nutritional epidemiology

• Exclusively breasts fed infants consume less thiamine, riboflavin, and vitamin D than the minimal daily requirements and have been shown to be at greater risk for autism as compared to mothers participating in nutritional programs.
• A controlled study found that autistic kids have lower intake of vitamin D, protein, calcium, and vitamin B12 as compared to controls.

Autism and skin color

• Higher risk in kids of dark skinned mothers may in part be explained by reduced vitamin D levels since darker skin requires greater sun exposure for vitamin D synthesis and the risk is exacerbated in moms who have migrated to colder, higher altitude areas.
• Effect of season of birth and effective latitude suggest role of maternal vitamin D in risk for autism. 

Dr. Minocha's comments on data and what to do?

In the absence of large randomized controlled trials, the issue remains open to debate.

The balance of data favors the hypothesis of involvement of vitamin D deficiency in pathogenesis of autism.

Given the limited data and widespread role of vitamin D in many organs including nervous system, it is prudent to maintain adequate levels of vitamin D.

• Note however, that what constitutes "normal" is mired in scientific debate.
• I recommend that all patients with low or low normal vitamin D levels receive vitamin D supplementation.
• Always talk to your doctor prior to taking such supplements.

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