Study under review: The Gluten-Free/Casein-Free Diet: A Double-Blind Challenge Trial in Children with Autism
Interest surrounding gluten-free/casein-free (GFCF) diets for children with autism spectrum disorder (ASD) has been growing for decades. The first trial to test a gluten-free diet on children with ASD was published in 1971. A few years later, a 1977 case study from The Johns Hopkins University School of Medicine was the first to eliminate both milk and gluten products from the diet, in this case of a 9-year-old boy with ASD.
Since then, GFCF diets have become one of the most popular dietary treatments chosen by parents who have children with ASD. Many surveys have attempted to determine the prevalence of GFCF diets as an alternative treatment, but results have been wide ranging. An average of these rates gives us an estimated 35% prevalence of GFCF diets, including both current and previous use. Parents with ASD children on a GFCF diet often report seeing improvements in behavior.
The prevailing concept in support of a GFCF diet is the ‘opioid-excess theory’ of ASD, depicted in Figure 1. This theory states that the incomplete breakdown of gluten and casein proteins into excess opioid peptides can trigger symptoms in people with ASD. Gluten proteins are found in products like wheat, barley, and rye, while casein proteins are found in dairy products. When ingested, gluten and casein are broken down into peptides (short chains of amino acids) such as gluteomorphin/gliadorphin or beta-casomorphin. These peptides could potentially cross through an abnormally permeable intestinal border, often referred to as a ‘leaky gut’, fully intact and undigested. If sufficient quantities were produced, these peptides could theoretically cross the blood-brain barrier, affecting the central nervous system and interfering with brain development, attention span, learning capacities, and cognitive function in people with ASD. It is therefore hypothesized that removal of these proteins from the diet could cause the behavioral symptoms of ASD to improve.
Like any theory, the opioid-excess theory of ASD does have its weak points. The biggest issue is a lack of consistent results. For example, some studies have noted an increased presence of gut permeability in people with ASD, while others have seen no difference. Further trials have seen increased gut permeability, but only in a specific subset of children with ASD. Additional doubt has been cast on this theory due to the consistent lack of detectable concentrations of opioid peptides in urine samples of patients with ASD using highly-sensitive measurement techniques. If significant amounts of opioid peptides were making it past the gut and into the bloodstream, urine tests would reveal their high levels as the body worked to eliminate them.
Regardless of the points for or against the opioid-excess theory, the biggest question is: does the dietary elimination of casein and gluten actually help to alleviate symptoms in people with ASD? The present rigorously-controlled study aims to shed further light on that matter.
Gluten-free/casein-free (GFCF) diets are a popular alternative treatment among parents who have a child with autism spectrum disorder (ASD). Many parents have reported seeing behavior improvements when their child is on a GFCF diet. The opioid-excess theory of ASD proposes that the opioid peptides produced from incomplete breakdown of gluten and casein proteins cross into the body and alter brain functions, causing the symptoms of ASD. The study under review uses rigorous methodology to test if a GFCF diet can provide ASD symptom relief.
Other Articles in Issue #13 (November 2015)
What are you feeding your bacteria?
While probiotics get most of the press, prebiotics arguably have more potential for altering one’s microbiome. This study looks at a promising type of prebiotic supplement to see if it might impact appetite and inflammation.
Breakfast: A disempowering nutritional dogma
By Martin MacDonald, Msc
Return of the globule: milk fat strikes back
Milk fat is structurally different than most other fats, and the milk fat globule membrane has been looked at previously (twice in Study Deep Dives, in fact) for its impact on chronic disease. But could it also impact response to exercise?
Studies have shown that supplement buyers generally trust the supplements they buy. That might not be the safest assumption, as dietary supplements that are presumed helpful or neutral may sometimes cause serious side effects, as quantified by this study.
Probiotics and the propensity for portliness
When you eat a meal, your gut bacteria also eats a meal. And gut bacteria are increasingly looked at for their influence on chronic disease. This study looks at the effect of a specific probiotic blend on weight gain.
The espresso effect: caffeine and circadian rhythm
Your daily rhythms are influenced by “zeitgebers” such as light and exercise. But until now, we haven’t known the exact impact of late-day caffeine intake on melatonin and circadian rhythms.
Money, time, and the science that suits us
By David Katz, MD, MPH
Human eating patterns ... there’s an app for that
Eating throughout the day has become quite normal, given the ubiquitous availability of snack foods. Partly due to this, diet research has been plagued by inaccurate self-reports. This study used an app to get around that issue.
Does marijuana actually boost creativity?
Ancedotally, weed has been claimed as a creativity booster for decades. With THC having an effect on dopamine, a plausible mechanism exists. This randomized trial puts marijuana to the test.