Dietary Supplements for Autism

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Dietary Supplements for Autism

Vitamin C, vitamin D, and omega-3 fish oil supplements put to the test to improve the core symptoms of autism spectrum disorder.


Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Dietary supplements are commonly given to children with autism. Do they do any good? One of the most common is omega-3 fats in the form of fish oil, based on studies like this that show “a marked reduction” in omega-3 blood levels among autistic children. But maybe that’s reverse causation—instead of the low omega-3s leading to autism, maybe the autism led to low omega-3s. Maybe autistic children are just pickier eaters and not eating as much fish or flax seeds. You don’t know until…you put it to the test.

Six months of 200 mg a day of DHA, one of the long-chain omega-3s, and… no effect. So here, all these kids are taking it, despite the lack of evidence that it actually does any good. Maybe they just didn’t give enough? Okay, how about a randomized, placebo-controlled trial of 1,500 mg of long-chain omega-3s. And, a high dose didn’t work either. Put all the studies together, and omega-3 supplementation simply “does not [appear to] affect autism.”

Here is a preliminary trial that was published of vitamin C supplements for autism that suggested benefit in at least some kids, but “should not be interpreted as a blanket recommendation for [vitamin C] supplementation”—especially at the whopping dose they used, which could increase the risk of kidney stones.

Bottom line, read a 2017 review in the journal of the Academy of Pediatrics: “There is little evidence to support the use of nutritional supplements” for children with autism, though they didn’t review the vitamin D data.

The vitamin D story started out, like the omega-3 story, with clear evidence that vitamin D blood levels were “significantly” lower in children with autism compared to other kids, and lower D levels correlated with greater autism severity. But vitamin D is the sunshine vitamin. Rather than vitamin D playing some role in autism, isn’t it more likely that autistic kids just aren’t out sunbathing as much?

There were some promising case reports, though. For example, this two-year-old with autism, deficient in D, whose autism seemed to improve after vitamin D supplementation. But, you don’t know if it’s a fluke until…you put it to the test.

A study on the efficacy of vitamin D supplementation in 83 autistic children, and… 80% got better, in terms of their “behavior,…eye contact,…attention span,” concluding: “Vitamin D is inexpensive, readily available,…safe,” and “may have beneficial effects.” But, this was an open-label trial, meaning no placebo control group. So, we don’t know how much of the improvement was just the placebo effect. Now sometimes, open-label experiments are unavoidable. Like, if you’re studying the effects of physical therapy or something, it’s hard to come up with like a placebo massage. But, you can stick vitamin D in a pill. Why not then do a proper randomized, double-blind, placebo-controlled trial?

The typical excuse you get is that it wouldn’t be ethical. If you have a kid who was vitamin D-deficient, how could you just stand by and give them a sugar pill? Yeah, but if vitamin D actually works, how many kids are you condemning to continue to suffer unnecessarily by publishing a less-than-ideal study design?

There are a bunch of “various tenable mechanisms” by which vitamin D could potentially help in children with autism: improvement in “DNA repair, anti-inflammatory actions,…mitochondrial protection,” etc. That’s why “randomized controlled trials are urgently needed.” But there haven’t been any such studies…until now.

A “[r]andomized, controlled trial of vitamin D supplementation in children with autism,” and it’s about time. They gave kids up to 5,000 international units a day, depending on their weight, versus a placebo. The drugs we have for autism really just help with some of the “associated symptoms.” Like, we can give kids sleeping pills or something, but there’s no drug that really touches “the core symptoms” of autism.

So, research groups around the world are looking for something better, and this group appeared to find it. “[V]itamin D supplementation revealed significant effects on the core manifestations of [autism spectrum disorder],” “significant improvements in [not only] irritability [and] hyperactivity [but] social withdrawal,” and repetitive behaviors, “and inappropriate speech”—the first double-blinded, randomized, controlled trial proving the efficacy of vitamin D in autism…patients.”

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