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Pregnant women are often encouraged to supplement their folic acid intake to prevent birth defects, but too much may also carry risks, according to a new study which links excessive folate and vitamin B12 to a greater risk of autism in the child. But the findings come with important caveats.

Why it matters:

Pregnant women need adequate folate, a type of vitamin B, to promote healthy neurodevelopment of their babies. However, the effects of excessive folate haven’t been well-studied.


The nitty gritty:

From 1998 to 2013, researchers gathered data from nearly 1,400 mother-child pairs enrolled in the Boston Birth Cohort. The researchers asked women about their vitamin intake and measured their blood levels of folate and vitamin B12 after giving birth. Researchers at the Johns Hopkins Bloomberg School of Public Health subsequently analyzed that data and noted that mothers with excessive levels of these nutrients in their blood had a higher risk of their child developing autism. Women with more than four times the adequate amount of folate had double the risk, high B12 levels tripled the risk, and high levels of both increased the risk by 17.6 times. The findings were presented on Wednesday at the International Meeting for Autism Research

But keep in mind:

This research is being presented at a conference, so it hasn’t gone through peer review. That means its findings should be taken with a grain of salt.

Since the women in the study were predominantly from urban minority populations, generalizing the findings to a population level is tricky. Also, since folate levels in blood are not regularly measured in pregnant women, “we don’t at a population level know what the average amount of folic acid in a pregnant woman might be,” explained Dr. Cynthia Gyamfi-Bannerman, associate professor of obstetrics and gynecology at Columbia University Medical Center Maternal-Fetal Medicine.


What they’re saying:  

While this study adds to our understanding, the medical evidence surrounding the relationship between folic acid and autism is still inconclusive, said Gordon Ramsay, assistant professor in the department of pediatrics at the Emory University School of Medicine. Some studies have found a relationship between lower folic acid intake and risk of autism spectrum disorders, other studies found a relationship between higher folic acid intake and risk of the same. “The literature is completely inconsistent. … It means that we don’t know what the real story is,” he explained.

You’ll want to know:

Vitamins are still important during pregnancy. Researchers found that taking multivitamins three to five times a week during pregnancy was associated with a lower risk of autism.

The American Congress of Obstetricians and Gynecologists recommends that pregnant women get at least 600 micrograms of folic acid daily from all sources. “Staying within the current parameters would be both prudent and important until we have more information to confirm these findings,” said Gyamfi-Bannerman.

The bottom line:

Consuming much more folate or vitamin B12 than the guidelines may be harmful to a developing fetus, but more studies will be needed to bear that out.

  • You’re doomed if you do doomed if you don’t, my son was born with a bilateral cleft lip and palate and I had 400 iu per day, it’s over the counter. Now the recommendation would be to go for 5mg to avoid birth defects…the data isn’t clear cut.. you can try and prevent autism but might get a different condition through a deficiency… the middle ground is the best.

  • Hi..Am 30 weeks pregnant women..Am continuously taking folic acid 5mg daily till now.. 2 days back I searched google do I found out that folic acid tablets also have sideeffects..6 month onwards I am having nausea..I didn’t bother that…I thought this is a pregnancy symptoms when I stopped folic acid my nausea is completely stopped.. tomorrow 8 month is going to start…pls I is there any problem..pls reply me pls

    • You don’t have to worry as 5mg is what most maternal doctor recommends as they say not all 100% of the folic acid will be absorbed in your body with the baby. You should cut down on the folic acid since your 6 months already.

  • We know folic acid affects the neurological systems of babies.

    Consider this graph of women becoming aware of needing to take folic acid supplements:

    Awareness increased substantially after 1992.

    The FDA mandated folic acid fortification in US foods in the early 1990’s:

    Look at the increase in autism since the early 1990s:’-science-staff-2/

    In comparison to the number of Spina Bifuda rates:

    While we have reduced Spina Bifida rates from 26 kids per 100,000 in 1991 to around 5-1 today, we have increased our autism rates from 1 kid per 5000 in 1975 to around 1 kid in 59 today.

    I’m glad they’re looking into it. Like most things, I’m sure we will find that folic acid is good only in moderation.

    Also consider this on supplements:

    Most doctors have no idea what they are prescribing pregnant women. Why? Because supplements are not regulated. Your most well known brands put a percentage and an amount on the canister, and those values have been tested by outside labs and found to be consistently over and under reported by an extreme amount.

    So this may not be your doctor’s fault but the unregulated supplement company’s fault. If no outside regulatory agency is checking and verifying and collecting complaints, there’s no reason to really be accurate.

    Want to see how outlandish these companies are in recording what is actually in their supplements? Go here and read the reports on prenatal vitamins from top brands in the US:

    Read this article written by a well regarded lab that tests supplements

    “Folic acid is a synthetic form of the B vitamin folate (B9) which naturally occurs in foods, such as green leafy vegetables. Folate can help reduce the risk of your baby being born with spina bifida (a leading cause of childhood paralysis) and other birth defects. While most adults need 400 mcg of folate daily, pregnant women need 600 mcg. To be sure you get this, it’s suggested that you take a supplement with 400 mcg of folic acid and that you get the rest of your folate from your diet — from foods such as dark green leafy vegetables, oranges, and grain products enriched with folic acid.

    Unfortunately, many prenatal supplements provide 800 mcg or more of folic acid — double the recommended amount from a supplement. That’s not all. Folic acid is absorbed much better (about 70% better) than folate from foods. This means that a prenatal supplement with 800 mcg of folic acid gives you the equivalent of 1,360 mcg of folate. (Labels will start making this clear 2018, but current labels don’t). On top of this, many manufacturers put in extra folic acid (30% or more is not uncommon), so it’s quite possible that your supplement which lists 800 mcg of folate from folic acid is giving you the equivalent of about 1,800 mcg of folate. Add to that the 300 to 400 mcg of folate you’re likely already getting from foods and you can see that this can easily total of over 2,000 mcg of folate per day!

    The upper tolerable intake level (UL) for folate is 1,000 mcg (which applies only to that consumed from supplements and fortified foods from synthetic forms like folic acid) — so any supplement with more than 586 mcg of folic acid will cause you to exceed the limit. It’s best not to exceed this because prolonged intake of excessive folic acid can cause kidney damage and can complicate the diagnosis of vitamin B-12 deficiency (folic acid supplementation can mask a symptom of vitamin B-12 deficiency). Of particular concern to pregnant women is that excessively high blood levels of folate (>59 nmol/L) in their blood was found to be associated with an approximate twofold increased risk of autism in their children according to an observational study in Baltimore in which 10% of women exceeded this level (Raghavan, International Meeting for Autism Research 2016). The study also found that when blood levels of both folate and vitamin B-12 were excessively high, the risk of autism was 17.6 times greater. (Note: Getting adequate folate during pregnancy may reduce the risk of autism; the concern is with getting too much).

    So what should you do? has tested and compared many prenatal supplements and other multivitamins. Unfortunately, most on the market tested by CL to-date have too much folic acid (more will be tested in mid-2017). For now it may be safest to skip a “prenatal” vitamin with 800 mcg of folic acid and, instead, choose a daily multivitamin which provides 400 mcg of folic acid. The multi should also provide other nutrients of particular importance during pregnancy such as iodine (150 mcg), vitamin D (600 IU), and calcium (1,000 mg per day is the daily requirement, but don’t take more than 500 mg at a time from a supplement). A challenge, however, is getting adequate iron, since the daily requirement during pregnancy (27 mg) is higher than for other pre-menopausal women (18 mg). A women’s multi can provide all the nutrients listed above, but typically just 18 mg of iron, so you’ll need to get extra iron from your diet. Alternatively, you can choose another multi and take a separate iron supplement providing about 27 mg of iron.”

  • I took folic acid with my first 1mg/day regularly and she is bright and healthy. There is alot about Autism we don’t understand yet so jumping to a quick conclusion doesn’t serve much good. As with everything too much can be harmful.

  • I have been saying for 15 years that there has to be a connection between autism and folic acid. I believe that there is a goldilocks zone with folic acid where too little and too much are not good for you. I saw studies were lab animals were given too much folic acid and their necropsies showed abnormal brains. I wish I wrote down the name of the scientist but I’m sure it can be found. My nephew has autism and my sister took folic acid religiously. Her second child doesn’t have it probably because she didn’t take the vitamins. I didn’t take vitamins for both my pregnancies and both my children are fine. I hope someone sees this.

    • Thank you for you comment i had concerns about vitamins with my pregnancy. If you are taking the vitamins regular and also eating foods with folic acid then that is putting you over recommended value for the day which is putting you at risk. I believe we are safer to just eat healthy like most women do any way. Why suppliment something that we take in on daily basis anyway.

    • This is really sad because I took folic acid prenatal vitamins when I was pregnant my son and he does have a speech delay no diagnosis yet with my now pregnancy I took it for the first 7 months I recently stopped after I seen these post and YouTube videos about folic acid I feel betrayed by the doctors and nurses for not notifying me and other mother’s about the rest of too much folic acid causing autism .thank you!

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