Folate and autism risk

Folic acid is added to all refined flour

Folic acid is added to all refined flour

The phrase “autism risk” is certain to grab the attention of pregnant women and new parents.  We always assume this type of risk is linked to bad-sounding things like chemicals, bad diet or substance abuse.  But what happens when something healthy turns out to carry risk?  That’s the case with a new study that found a potential link between blood folate levels and autism risk.

Folate is a B-vitamin, essential for health and critical for pregnant women because it plays a key role in cell division and fetal growth.  Spina bifida, a birth defect caused by defects in neural tube development, was linked to poor folate intake many years ago.  Neural tube defects can be prevented easily by adequate folate intake during pregnancy.  Unfortunately, plenty of pregnant women have poor intake of folate-rich foods like fruits and vegetables.  So once the link to spina bifida was established, health experts tried to by-pass poor food choices by adding folate to a food that most everyone eats: flour.  This fortification, using the folic acid form of the vitamin, has been in effect since 1998.  The impact was immediate: average daily intake increased to 350 micrograms/day (the recommended intake is 400 mcg) and blood folate levels increased for everyone.  Incidence of neural tube defects in newborns dropped.

Now we seem to have a new problem.  The implication is that high blood folate would be caused by excess intake.  But it’s not always the case that a person’s intake of a nutrient impacts blood levels.  The human body has control systems to prevent toxic levels of many nutrients.  Water soluble vitamins, like C and B’s, are flushed out by the kidneys very quickly.  Mineral absorption from the intestines can be increased or decreased according to need.  Folate is a water-soluble vitamins, so you could assume excess levels would be excreted.  So why would blood levels be elevated?

One theory is that those women consumed too much folate, from supplements and from food.  But the study didn’t conclude that.  Some of the women who took supplements had normal blood folate.  For women who took prenatal supplements 3-5 times/week, risk for autism in their children was actually lower.

Another possibility is that some women have a tendency to higher blood folate, for reasons that have nothing to do with intake.  Vitamin metabolism and utilization could be impacted by genetics.  There could be some more basic issue that increases risk for autism, and one sign of this is high blood folate.  In other words, the folate isn’t the cause, it’s a sign.

There’s a non-genetic cause of high folate that has not been mentioned in this study: Small Intestinal Bacterial Overgrowth.  SIBO is overgrowth of bacteria in the upper GI tract, where they don’t belong.  It can be an ongoing problem for some people, or a complication of some other medical problem.  It causes lots of unpleasant symptoms, and one unusual clinical feature is elevated blood folate.  Why? Because the overgrowing bacteria actually make folate, which is then absorbed, leading to elevated levels.  While SIBO isn’t linked to pregnancy or autism, I’m presenting this as an example of how blood level of a vitamin may have no relationship to how much a person consumes.

There’s one more twist on this particular study.  B12 levels were also measured and the children of women with elevated B12 and folate were most at risk for developing autism.  Unlike folate, B12 is not added to foods.  And it’s not produced by bacterial overgrowth.  B12 absorption is tightly controlled by a molecule called Intrinsic Factor.  So this finding is even more mysterious.

The main point is, for pregnant women, adequate folate is important for fetal development.  You should not avoid folate or B12 because you’re worried about autism.  If you’re concerned, you should discuss the issue with your obstetrician and come up with a plan.  Perhaps you will have your blood tested, or keep track of your total folate or B12 intake.  Prenatal supplements have both these vitamins, and fortified foods have folic acid.  B12 is found exclusively in animal-sourced foods like meat, dairy and eggs.  Foods naturally high in folate are fruits and vegetables, which you should be eating more of anyway, such as:

  • green leafy vegetables like spinach
  • asparagus
  • broccoli
  • peas
  • tomatoes
  • oranges
  • kidney beans and other legumes
  • cantaloupe melon

Here’s the thing that annoys me about folic acid fortification: if you eat a healthy diet and get plenty of folate from fruits and vegetables, you are literally forced to eat even more from foods made with fortified flour.  You cannot avoid it.  And to further complicate the picture, folic acid (used for fortification) is more biologically potent than folate present naturally in fruits and vegetables.  Folic acid fortification was meant to protect the infants of women who can’t be bothered to eat high folate foods, but we all have to participate in this solution.

What does it all mean for a pregnant woman?

There’s nothing in this study that says high folate/B12 causes autism.  It’s an association.  More research is needed to clarify what’s going on.  We do know that both B12 and folate are essential for health and very important for pregnant women.  Eating foods high in natural folate and B12 is important.  Prenatal supplements will have both of these nutrients.  You may chose to avoid products with excessively high levels of either.  You should discuss the options with your doctor or better yet, consult with a registered dietitian about your diet and nutrient intake.

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