Vitamin D Deficiency During Pregnancy Raises Your Child’s Risk for Autism

Story at-a-glance

  • Recent research shows vitamin D deficiency during pregnancy is associated with an increase in autism-related traits in 6-year-old children. Deficiency was defined as vitamin D level below 25 nmol/L (10 ng/mL)
  • Vitamin D regulates a gene responsible for conversion of tryptophan into serotonin. Serotonin is crucial during fetal brain development. When vitamin D is lacking, low serotonin can produce neurological defects
  • Vitamin D optimization during pregnancy may also cut your risk of premature birth in half, and lower your child’s risk of multiple sclerosis


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

There has been a dramatic and concerning increase in the rates of autism spectrum disorder (ASD) over the last 30 years and experts believe the rates will continue to increase.

When I was in medical school more than 35 years ago, the incidence of autism was 1 in 10,000.

According to a 2013 report by the U.S. Department of Health and Human Services (DHHS) and the Centers for Disease Control and Prevention (CDC), data collected from the 2007 and 2011–2012 National Survey of Children's Health suggested 1 in 50 children between the ages of 6 and 17 had ASD.1,2

In April 2016, the CDC reported an ASD rate of 1 in 68.3 However, that rate is only based on 8-year-olds in 11 states (Arkansas, Arizona, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, South Carolina, Utah and Wisconsin).

Despite that limitation, the 1 in 68 prevalence is the one listed on the CDC's Autism Data and Statistics website,4 and the one most frequently reported in the news. Meanwhile, a government survey issued in 2015 claims the ASD rate may be as high as 1 in 45 children between the ages of 3 and 17.5,6

What's Causing the Rapid Rise in Autism?

Disturbingly, the CDC also reports that an astounding 1 in 6 children have some form of developmental disability, ranging from speech and language impairments to more serious intellectual disabilities, including autism and cerebral palsy.7

According to projections by Stephanie Seneff, Ph.D., a senior research scientist at MIT, within the next two decades, half of all children born will have some form of autistic disorder if the current trend continues unabated.8

If this projection ever materializes it spells the end of our country. Without some sort of advanced artificial intelligence there is no way any country can survive, let alone thrive, with half of the adults being autistic. So what is responsible for this epidemic?

Mounting research indicates that brain disorders are the result of excessive exposure to toxins, including the commonly used weed killer Roundup, both during pregnancy and after birth.

Two other critical factors appear to be related to damaged gut microbiome and vitamin D deficiency, the latter of which is the focus of this article.

Vitamin D Deficiency During Pregnancy Raises Autism Risk

For a time, the idea that vitamin D deficiency might play a role in autism was little more than a logical suspicion, based on the fact that the human brain contains vitamin D receptors, suggesting vitamin D is important for proper brain development and function.

Mounting research is now starting to validate this hypothesis. Most recently, a large multi-ethnic population-based cohort study9 published in Molecular Psychiatry found that vitamin D deficiency during pregnancy was associated with an increase in autism-related traits in 6-year-old children.

The study, which has garnered wide international media attention,10,11,12,13,14,15,16,17 is the first study examining the association between gestational vitamin D deficiency and autism or autism-related traits in general population samples. According to the authors:

"[T]hose who were 25OHD [25-hydroxyvitamin D] deficient had significantly higher (more abnormal) SRS [Social Responsiveness Scale] scores.

The findings persisted (a) when we restricted the models to offspring with European ancestry, (b) when we adjusted for sample structure using genetic data, (c) when 25OHD was entered as a continuous measure in the models and (d) when we corrected for the effect of season of blood sampling …

It is feasible that a safe, cheap and publicly accessible vitamin D supplement in at risk groups may reduce the prevalence of this risk factor.

Just as prenatal folate supplementation has reduced the incidence of spina bifida, we speculate that prenatal vitamin D supplementation may reduce the incidence of autism."

Two Important Considerations

All of the mothers enrolled in the study gave birth between April 2002 and January 2006. The children were then followed until the age of 6.

Vitamin D levels were assessed at mid-gestation (between 18 and 25 weeks) from maternal blood samples, and cord blood at birth. There are two points I'd like to highlight regarding this study.

1. Vitamin D deficiency was defined as a 25OHD concentration below 10 nanograms per milliliter (ng/mL) or 25 nmol per liter (nmol/L). A vitamin D level between 10 to 19.96 ng/mL (25 to 49.9 nmol/L) was deemed insufficient, while a level of 20 ng/mL (50 nmol/L) or more was sufficient.

Other leading vitamin D researchers have produced compelling evidence showing that anything below 40 ng/mL (100 nmol/L) is insufficient, and anything below 20 ng/mL (50 nmol/L) is a deficiency state.

If these higher levels had been used here, it could potentially have resulted in an even greater correlation between ASD symptoms and vitamin D status. For a healthy pregnancy and baby, I strongly recommend making sure your vitamin D level is between 40 and 60 ng/mL (100 and 150 nmol/L).

2. The 25OHD concentration in this study was defined as the sum of 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3), measured in blood.

This means it included all sources of vitamin D, be it from sun exposure, supplements and/or foods. Vitamin D2 would be from irradiated plant sources and D3 is from animal sources.

However, when it comes to raising your vitamin D level, there's reason to suspect that swallowing vitamin D (either as D3 or D2, the latter of which has actually been shown to have significant drawbacks or side effects18) may not provide the same benefits as sensible sun exposure.

To learn more about this difference, please see my previous interview with Seneff. If you, for whatever reason, cannot obtain sufficient sun exposure year-round to raise or maintain optimal levels, then a vitamin D3 supplement is certainly advisable.

It's better than nothing, but ideally, to obtain ALL the benefits of vitamin D, aim for sensible ultraviolet (UV) exposure while being very careful not to get sunburned.

Remember that vitamin D is an indirect biologic marker of UVB exposure and you are likely to disrupt important and many as-yet-undiscovered mechanisms if you trick your body by obtaining vitamin D without sun exposure.

One that we are currently aware of is that you will miss the near-infrared radiation from sun UVB exposure, which balanced the UVB and has many important functions. Near-infrared radiation will activate cytochrome C oxidase in your mitochondria and help to optimize ATP production among many other important functions.

How Vitamin D Influences Autism

Biological scientist Rhonda Patrick, Ph.D., has published two papers19,20 that present a truly elegant hypothesis for how vitamin D may influence autism. To understand why vitamin D plays such an important role in brain function (and dysfunction), it's important to understand that vitamin D actually gets converted into a steroid hormone (other steroid hormones include estrogen and testosterone).

As a steroid hormone, it regulates over 1,000 different physiological processes, and is thought to control at least 5 percent of the human genome. When you have enough vitamin D in your body, it binds to vitamin D receptors located throughout your body, thereby acting like a key that opens the proverbial door.

The vitamin D receptor complex can go deep inside the DNA, where it recognizes the tell-tale sequence of code that instructs the vitamin D receptor complex to either turn the gene on (making it active), or off (making it inactive).

Patrick's research identified a vitamin D-regulated gene that encodes a foreign enzyme called tryptophan hydroxylase (TPH). TPH is responsible for converting tryptophan (which you get from dietary protein) into serotonin, a neurotransmitter involved in both mood regulation and brain development.

You have two different TPH genes in your body — one in your brain and one in your gut. The one in your brain makes serotonin in the brain, and the one in your gut converts tryptophan into serotonin in the gut, and the latter cannot cross the blood-brain barrier to get into your brain.

This is an important point because, while many understand that the majority (about 90 percent) of the serotonin in your body is produced in the gut and not the brain, the thinking has been that the gut serotonin will automatically influence brain function.

Since it's unable to cross the blood-brain barrier, this is not the case. The two serotonin systems are completely separate. Your gut serotonin plays a role in blood coagulation, which is an important benefit. On the other hand, too much gut serotonin will activate T-cells, causing them to proliferate and promote inflammation.

Vitamin D Keeps Gut Serotonin in Check

What Patrick discovered is that, in the gut, vitamin D deactivates the gene responsible for making TPH (the enzyme that converts tryptophan into serotonin). In this way, vitamin D helps combat inflammation in your gut caused by excessive serotonin levels.

Meanwhile, in the brain, the tryptophan hydroxylase gene has a sequence that causes the opposite reaction. Here vitamin D activates the gene, thereby increasing serotonin production! Needless to say, when you have sufficient amounts of vitamin D, two things happen simultaneously:

  1. Gut inflammation is reduced, courtesy of deactivating the gene associated with serotonin production.
  2. Serotonin levels in the brain are increased by gene activation, and in the brain, serotonin plays an important role in mood, impulse control, long-term planning, long-term behavior, anxiety, memory and many other cognitive functions and behaviors, including sensory gating — the ability to filter out extraneous or unimportant stimuli.

Since the publication of Patrick's first paper21 in 2014, an independent group at the University of Arizona has biochemically validated her findings, confirming that vitamin D does activate the tryptophan hydroxylase 2 (TPH2) gene in a variety of neuronal cell types.

Prior to the publication of that paper, this simply wasn't known, and it's a significant finding that can help shed a great deal of light on vitamin D's influence in autism, as a majority of autistic kids have not only brain dysfunction, but also gut inflammation. Her research clearly shows how important it is to have enough vitamin D to prevent and treat both of these problems. To learn more, please listen to Patrick's interview, included above for your convenience.

Low Vitamin D Associated With Multiple Sclerosis

Vitamin D is crucial during pregnancy for many other reasons as well. Research has shown that children born of women with adequate levels of vitamin D have a lower risk for multiple sclerosis (MS) and other autoimmune conditions like inflammatory bowel disease and type 1 diabetes, in childhood and later life.

A recent Danish study22,23 showed that newborns with vitamin D levels above 20 ng/mL (50 nmol/L) were 47 percent less likely to develop MS by the age of 30 compared to those with vitamin D levels below 12 ng/mL (30 nmol/L) at birth. MS is a chronic, neurodegenerative disease of the nerves in your brain and spinal column, caused through a demyelization process. It has long been considered a "hopeless" disease with few treatment options.

A study24,25 presented at the annual meeting of the American Association of Neuromuscular and Electrodiagnostic Medicine26 (AANEM) in 2014 showed that vitamin D deficiency is surprisingly prevalent among those diagnosed with MS and other neuromuscular conditions. Here, vitamin D deficiency was defined as a 25OHD3 level of 30ng/mL (75 nmol/L) or less.

Of patients diagnosed with a neuromuscular condition, 48 percent were deficient in vitamin D. Only 14 percent were above "normal," which here constituted a vitamin D level of 40 ng/mL (100 nmol/L). According to one of the authors:

 "While the connection between vitamin D deficiency and neurologic disease is likely complex and not yet fully understood, this study may prompt physicians to consider checking vitamin D levels in their patients with neurologic conditions and supplementing when necessary."

Besides this one, about a dozen other studies27 have also noted a strong link between MS and vitamin D deficiency. For example, a number of studies have confirmed that your risk of MS increases the farther away you live from the equator, suggesting lack of sun exposure amplifies your risk.

Vitamin D Optimization May Slash Risk of Premature Birth in Half

Each year, more than half a million preemies are born in the U.S., and it's the No. 1 killer of newborns.28 Research shows that half of these premature births could be easily prevented simply by raising pregnant women's vitamin D levels.29 Among African-American and Hispanic populations, as much as 70 to 75 percent of all preterm births might be prevented.

Similar findings have been documented among twin births, which tend to have a higher risk for preterm birth. A 2013 study30 found that women carrying twins who had a minimum vitamin D level of 30 ng/mL (75 nmol/L) in their late second trimester had a 60 percent reduction in preterm births.

According to a 2015 paper31 produced by researchers from GrassrootsHealth and the Medical University of South Carolina, women with vitamin D levels of 40 to 60 ng/mL (100 to 150 nmol/L) have a 46 percent lower preterm birth rate than the general population. Women with a vitamin D level at or above 40 ng/mL (100 nmol/L) by their third trimester had a 59 percent lower risk for premature birth than those with levels below 20 ng/mL (50 nmol/L).

Moreover, as noted in a press release:32 "Another key finding was a steady increase of gestation time (how long the baby stayed in the womb) correlating to the rise of vitamin D up to around 40 ng/mL where it reached a plateau."33 In other words, 40 ng/mL or 100 nmol/L is "the magic level" for the prevention of premature birth. Yet another 2015 study34 found the following correspondences between vitamin D levels and premature birth (less than 37 weeks of gestation):

  • Among women with a vitamin D level of less than 20 ng/mL (50 nmol/L) the incidence of preterm birth was 11.3 percent
  • Among those with a vitamin D level of 20 to 29.96 ng/mL (50 to 74.9 nmol/L) the preterm birth rate was 8.6 percent
  • Among those with 30 ng/mL (75 nmol/L) or greater, the preterm birth rate was 7.3 percent

Vitamin D — A Simple, Inexpensive Way to Improve Your and Your Child's Health

In the video above, Glen Depke interviews Dr. Carol Wagner, a neonatologist and lead principal investigator for Protect Our Children NOW!, a public health campaign aimed at raising global awareness about the importance of optimal vitamin D levels for women's and children's health. In it, Wagner cites research done by her team showing that 4,000 international units (IUs) of vitamin D3 per day appears to be an ideal amount for pregnant women.

That said, your requirement may be higher or lower depending on your current status, so please make sure you get your vitamin D level tested — ideally before you get pregnant and routinely during pregnancy and breastfeeding — and take whatever amount of vitamin D3 you need to reach and maintain a level of 40 to 60 ng/mL (100 to 150 nmol/L). Certainly, it should be no lower than 40 ng/mL (100 nmol/L).

I strongly suggest taking this information to heart, and to share it with anyone that might benefit. Optimizing your vitamin D is one of the easiest and least expensive ways to reduce your risk of complications and premature birth. It can also significantly reduce your child's risk of ASD, MS and other chronic health conditions.

The vitamin D test you're looking for is called 25(OH)D or 25-hydroxyvitamin D. This is the officially recognized marker of overall D status, and is most strongly associated with overall health. The other vitamin D test available, called 1,25-dihydroxy vitamin D (1,25(OH)D), is not very useful for determining vitamin D sufficiency.

While sunlight is the ideal way to optimize your vitamin D, winter and work prevent more than 90 percent of those reading this article from achieving ideal levels without supplementation. Just remember to also increase your vitamin K2 and magnesium intake, either from food or supplements and seek to move or vacation for long periods in the subtropics to get vitamin D naturally from sun exposure.


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