By Jennifer Copley (Last Updated 30 March 2012)
Vitamin D is known as the sunshine vitamin because sunshine is its best-known natural source. A high prevalence rate of vitamin D deficiency in recent years, combined with rising autism rates,* have led scientists to explore a possible connection between autistic spectrum disorders and vitamin D.
Evidence for Vitamin D’s Role in Autistic Spectrum Disorders
Dr. John Cannell, a U.S. researcher, observed that autism rates have been rising in conjunction with sun avoidance, which began when medical experts started warning people to stay out of the sun due to skin cancer risk. Because vitamin D is naturally obtained via sun exposure, Cannell has put forth the theory that vitamin D deficiency among mothers and infants may be responsible for the autism epidemic in recent years (Mittelstaedt, 3 April 2009). Evidence for the theory is circumstantial thus far, but there is quite a lot of it:
- Many studies have shown that children with autism are most often born during the spring, so from the later months of pregnancy to the time of birth, their mothers get little if any sun exposure; this creates a greater risk of vitamin D deficiency (Cannell, 31 May 2011).
- Eating vitamin-D-rich fish during pregnancy (even when that fish contains some mercury) is associated with reduced autistic markers in children (Cannell, 2008).
- Meguid et al. (2010) found vitamin D deficiencies in children with autism; however, it should be noted that vitamin D deficiency may be caused or worsened by atypical eating habits associated with autism, such as eating only a small selection of foods (Zimmer et al., 2012).
- Humble et al. (2010) found lower vitamin D levels in adults with autistic spectrum disorders.
- Autism rates are far higher in areas that get less intense sunshine, including not only the poleward latitudes but also areas where there is higher precipitation or air pollution (Cannell, 2008) and urban areas with tall buildings, indoor work, etc. (Cannell, 2010).
- Premature birth increases the likelihood of autism, and mothers deficient in vitamin D are more likely to give birth prematurely (Cannell, 31 May 2011).
- High levels of vitamin D may reduce the likelihood of infection during pregnancy, which may in turn reduce the risk of autism, though these connections have not been proven (Cannell, 17 May 2011).
- Oxidative stress is a hallmark of autism, and vitamin D has been shown to reduce oxidative stress (Cannell, 31 May 2011).
- Those with Williams syndrome, which produces many symptoms that are the opposite of those associated with autism (such as extreme sociability), often have elevated vitamin D levels as infants (Cannell, 2008).
- Children who have developed rickets due to vitamin D deficiency also have certain autistic markers that are eliminated with high-dose vitamin D supplementation (Cannell, 2008).
- The hormones testosterone and estrogen impact the way vitamin D is metabolized by the body, which may be the reason why far more males than females meet the diagnostic criteria for autistic spectrum disorders (Cannell, 2008).
- Vitamin D is probably critical to brain development due to its role in neural development and protection; it facilitates the beneficial antioxidant action of glutathione (which is often used as a complementary autism therapy), and it also plays a key role in anti-inflammatory processes (Deans, 11 September 2010).
- Studies of vitamin-D deficient animals have shown brain abnormalities similar to those of autistic children (Cannell, 2008).
- Somali immigrants Stockholm, Sweden, have autism rates 3-4 times higher than those of other immigrants living in Stockholm (darker skin, which is suited to warmer climates, requires more sunlight to obtain adequate vitamin D); this effect is so pronounced that Somalis in Stockholm call autism “the Swedish disease”– autism is virtually unknown in Somalia – there is not even a word for it there (Glasser, 24 April 2009).
None of this proves that vitamin D deficiency causes autistic spectrum disorders, but there is sufficient evidence to warrant further scrutiny. There is also some preliminary evidence that vitamin D deficiency may cause of a variety of illnesses ranging from cancer to multiple sclerosis (Mittelstaedt, 3 April 2009).
Cannell (2010) notes that the vitamin D theory doesn’t negate the contribution of genetics. Rather, he suggests that vitamin D deficiency may bring out an existing genetic vulnerability that wouldn’t have been expressed otherwise.
Cannell’s theory answers many frequently asked questions about autism, such as:
- Why are there prevalence differences between girls and boys and among different races?
- Why are autistic children at greater risk for infections and seizures?
- Why are mothers who eat seafood while pregnant less likely to have autistic children?
- Why do some autistic children make miraculous recoveries, particularly in response to fish oil or vitamin supplements?
- Why have autism rates increased so dramatically, particularly in North America and Europe, while remaining low near the equator?
- Why do autism symptoms tend to come on around the time that children are weaned from vitamin-D-rich breast milk or formula?
See the Vitamin D page for information on supplements, natural food sources of vitamin D, and obtaining vitamin D from sunshine.
Some parents of autistic children choose to supplement with vitamin A or cod liver oil. However, Dr. Cannell (10 August 2010) notes that this can interfere with the metabolism of vitamin D and recommends getting vitamin A from natural sources, such as colourful produce (yellow and orange vegetables and dark leafy greens tend to be the best sources).
The Vitamin D Council is a non-profit organization that is working to end the worldwide epidemic of vitamin D deficiency. To learn more about this organization’s work or make a donation, visit VitaminDCouncil.org.
Other Autism Supplements
For more on the effectiveness of various supplements for treating autistic spectrum disorders, see the main Autism Supplements page. For a full list of articles on autism and Asperger’s syndrome, visit the main Autistic Spectrum Disorders page.
*Some experts don’t believe that the autism rate has increased; instead, they argue that the rate has remained similar over the years, but heightened awareness and a loosening of the diagnostic boundaries has led to more children being diagnosed than in the past.
This article is not intended as a substitute for medical consultation or care. Health concerns should be referred to a doctor.
- Cannell, J.J. (2008). “Autism and Vitamin D.” Medical Hypotheses, 7(4), 750-759.
- Cannell, J.J. (2010). “On the Aetiology of Autism.” Acta Paediatrica, 99(8), 1,128-1,130.
- Cannell, J.J. (10 August 2010). “A Mother, Her Autistic Son, and Vitamin D: Case Summary.” Vitamin D Council, VitaminDCouncil.org.
- Cannell, J.J. (31 May 2011). “Introducing the Vitamin D Theory of Autism.” Vitamin D Council, VitaminDCouncil.org.
- Cannell, J.J., Vitamin D Council. (22 August 2011). “Autism – Patient-Friendly Summary.” VitaminDCouncil.org.
- Deans, E., MD. (11 September 2010). “Autism and Vitamin D.” Evolutionary Psychiatry, EvolutionaryPsychiatry.blogspot.com.
- Glasser, G. (24 April 2009). “What if Vitamin D Deficiency Is a Cause of Autism?” Scientific American, ScientificAmerican.com.
- Humble, M.B.; Gustafsson, S.; & Bejerot, S. (2010). “Low Serum Levels of 25-Hydroxyvitamin D (25-OHD) Among Psychiatric Out-Patients in Sweden: Relations with Season, Age, Ethnic Origin and Psychiatric Diagnosis.” Journal of Steroid Biochemistry and Molecular Biology, 121(1-2), 467-70.
- Meguid, N.A.; Hashish, A.F.; Anwar, M.; & Sidhom, G. (2010). “Reduced Serum Levels of 25-Hydroxy and 1,25-Dihydroxy Vitamin D in Egyptian Children with Autism.” The Journal of Alternative and Complementary Medicine, 16(6), 641-645.
- Mittelstaedt, M. (6 July 2007). “Researcher Sees Link Between Vitamin D, Autism.” The Globe and Mail, TheGlobeandMail.com.
- Zimmer, M.H.; Hart, L.C.; Manning-Courtney, P.; Murray, D.S.; Bing, N.M.; & Summer, S. (2012). “Food Variety as a Predictor of Nutritional Status Among Children with Autism.” Journal of Autism and Developmental Disorders, 42(4), 549-556.