Are Autism Diet Benefits Just a Placebo Effect?

Are Autism Diet Benefits Just a Placebo Effect?
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The original randomized, controlled trials of gluten- and casein-free diets may have been complicated by parental expectation bias.

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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.

The first randomized, controlled trial to put a gluten-free, casein-free diet to the test for children with autism reported significant improvements in attention problems, less aloofness, fewer needs for routines and rituals, and improved response to learning after a year on the diet—whereas, there was no significant difference reported before or after in the control group.

Same with improvements in social and emotional factors; significantly fewer problems with relationships with their peers, less anxiety, more empathy, and more acceptance of physical contact—but again, no significant changes reported in the control group.

Significantly fewer communication problems too; more facial expression, better eye contact, responsiveness, and fewer things like meaningless word repetition in the diet group—whereas, no significant changes in the control group.

And, in terms of cognitive factors and movement, after a year on the diet, there was significant improvement in the ability to judge dangerous situations, expanded personal interests, and lower likelihood of being inordinately restless or passive.

Now, the problem with this study is that they relied mostly on parental report. They asked parents questions like these, before and after the year-long trial, to see if they detected any differences.

Why is that a problem? I mean, who better knows the day-to-day functioning of children than their parents? Yeah, they could have had some impartial observer come in before and after to make assessments, blind to which group the children were in, but those would just be like snapshots in time. Who better than the parents to know what was going on with their children?

The problem is the placebo effect. I mean, here the parents are investing “a great deal of time and effort” to maintain these strict diets. I mean, there’s wheat and dairy in so many products that it’s a big shift for most families—and so, they have this hopeful expectation of an effect. So, while the families in the control group did nothing special that year, and reported no significant changes before and after, the families in the diet group put all this work in, and so, when asked if their kids appeared better, their opinions may have been “impacted” by their expectations of benefit. In other words, “placebo effects may have been at play.”

Oh, come on, though; are parents that gullible? Well, “the power of suggestion on the part of parents can be very strong in situations affecting their children’s behavior.” For example, there was this famous study in which all the children were given “a drink with artificial sweetener,” but half of the parents were told that the drink was sweetened with a boatload of sugar. And, “[t]he parents who thought their children had received the sugar-drink rated their [own] children’s behavior as significantly worse…”

So, in these autism studies, “[it’s] possible that parents [were unconsciously] looking for positive changes in behavior and ignor[ing] or explain[ing] away negative [changes].” So, ideally, what we need are double-blind studies—where kids are given foods made to look and taste the same, but one food has gluten and casein, and the other doesn’t. The kids don’t know which is which; the parents don’t know which is which. Even the researchers, at first, don’t know which is which—until they break the code at the end. “In this way, the behaviors recorded after the [food] challenges could not be impacted by preconceived ideas or biases.”

Okay. So, why didn’t this study do that? “With regard to design”, the researchers conceded, “it might be argued that a double blind…study might have been ideal. With all children on [the] diet, gluten and casein could have been [secretly] administered, for example, in capsules [with wheat flour or powdered milk] during specific altering periods. Then, “[p]arents and caretakers would…have been blind to who was [still] on [the] diet and who” was, unbeknownst to them, actually off the diet, secretly getting gluten and casein. Then, we could eliminate the placebo effect, eliminate that expectation bias. So, why didn’t they do it?

The researchers refused to do it because they were so convinced that gluten and casein were harmful, that from an “ethical” viewpoint, they just couldn’t bring themselves to give these kids gluten or casein. The kids in the diet group seemed to be doing so much better, and they had seen cases in which kids appeared to relapse when those proteins were reintroduced back into their diet. And so, they just couldn’t bring themselves to slip them any on the sly.

I understand that, but if they were really so certain that gluten and casein were bad, then by designing a less-than-ideal study, they were potentially dooming scores of other children by failing to provide the strongest possible evidence. Thankfully, four years later, other researchers stepped in and published the first double-blind clinical trial of diet and autism. We’ll find out what they found, next.

Please consider volunteering to help out on the site.

Image credit: Providence Doucet. Image has been modified.

Motion graphics by Avocado Video

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.

The first randomized, controlled trial to put a gluten-free, casein-free diet to the test for children with autism reported significant improvements in attention problems, less aloofness, fewer needs for routines and rituals, and improved response to learning after a year on the diet—whereas, there was no significant difference reported before or after in the control group.

Same with improvements in social and emotional factors; significantly fewer problems with relationships with their peers, less anxiety, more empathy, and more acceptance of physical contact—but again, no significant changes reported in the control group.

Significantly fewer communication problems too; more facial expression, better eye contact, responsiveness, and fewer things like meaningless word repetition in the diet group—whereas, no significant changes in the control group.

And, in terms of cognitive factors and movement, after a year on the diet, there was significant improvement in the ability to judge dangerous situations, expanded personal interests, and lower likelihood of being inordinately restless or passive.

Now, the problem with this study is that they relied mostly on parental report. They asked parents questions like these, before and after the year-long trial, to see if they detected any differences.

Why is that a problem? I mean, who better knows the day-to-day functioning of children than their parents? Yeah, they could have had some impartial observer come in before and after to make assessments, blind to which group the children were in, but those would just be like snapshots in time. Who better than the parents to know what was going on with their children?

The problem is the placebo effect. I mean, here the parents are investing “a great deal of time and effort” to maintain these strict diets. I mean, there’s wheat and dairy in so many products that it’s a big shift for most families—and so, they have this hopeful expectation of an effect. So, while the families in the control group did nothing special that year, and reported no significant changes before and after, the families in the diet group put all this work in, and so, when asked if their kids appeared better, their opinions may have been “impacted” by their expectations of benefit. In other words, “placebo effects may have been at play.”

Oh, come on, though; are parents that gullible? Well, “the power of suggestion on the part of parents can be very strong in situations affecting their children’s behavior.” For example, there was this famous study in which all the children were given “a drink with artificial sweetener,” but half of the parents were told that the drink was sweetened with a boatload of sugar. And, “[t]he parents who thought their children had received the sugar-drink rated their [own] children’s behavior as significantly worse…”

So, in these autism studies, “[it’s] possible that parents [were unconsciously] looking for positive changes in behavior and ignor[ing] or explain[ing] away negative [changes].” So, ideally, what we need are double-blind studies—where kids are given foods made to look and taste the same, but one food has gluten and casein, and the other doesn’t. The kids don’t know which is which; the parents don’t know which is which. Even the researchers, at first, don’t know which is which—until they break the code at the end. “In this way, the behaviors recorded after the [food] challenges could not be impacted by preconceived ideas or biases.”

Okay. So, why didn’t this study do that? “With regard to design”, the researchers conceded, “it might be argued that a double blind…study might have been ideal. With all children on [the] diet, gluten and casein could have been [secretly] administered, for example, in capsules [with wheat flour or powdered milk] during specific altering periods. Then, “[p]arents and caretakers would…have been blind to who was [still] on [the] diet and who” was, unbeknownst to them, actually off the diet, secretly getting gluten and casein. Then, we could eliminate the placebo effect, eliminate that expectation bias. So, why didn’t they do it?

The researchers refused to do it because they were so convinced that gluten and casein were harmful, that from an “ethical” viewpoint, they just couldn’t bring themselves to give these kids gluten or casein. The kids in the diet group seemed to be doing so much better, and they had seen cases in which kids appeared to relapse when those proteins were reintroduced back into their diet. And so, they just couldn’t bring themselves to slip them any on the sly.

I understand that, but if they were really so certain that gluten and casein were bad, then by designing a less-than-ideal study, they were potentially dooming scores of other children by failing to provide the strongest possible evidence. Thankfully, four years later, other researchers stepped in and published the first double-blind clinical trial of diet and autism. We’ll find out what they found, next.

Please consider volunteering to help out on the site.

Image credit: Providence Doucet. Image has been modified.

Motion graphics by Avocado Video

Doctor's Note

This is the fourth video in a six-part series on the role of gluten- and dairy-free diets in the treatment of autism. Here are the first three:

Stay tuned for:

I will continue to have autism videos coming out through 2018. Catch all of the latest here.

For videos about gluten-free diets in general, see Is Gluten Sensitivity Real? and How to Diagnose Gluten Intolerance.

If you haven’t yet, you can subscribe to my videos for free by clicking here.

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