Review of Double-blind Placebo-controlled Study On the GFCF Diet

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By Gita Gupta

 

Study Reports That the GFCF Diet is Nutritionally Safe  

A recent double-blind, placebo-controlled study by Hyman et al (2015) http://www.ncbi.nlm.nih.gov/pubmed/26343026 looked at the Gluten-free, casein-free (GFCF) diet and established that it is safe and does not carry any nutritional risk. The study excluded kids with ASD who have gastrointestinal symptoms. For other ASD kids, the study states that – “… the diet can be safe for other children with ASD if properly implemented and monitored for nutritional sufficiency.”

Study Reports Safety but no Behavioral Benefits From The GFCF Diet. Why?

In contrast to anecdotal reports from thousands of parents, the study found no benefits from the diet. One reason for the lack of positive results could be because the study’s approach to GFCF is very different from how the diet is implemented in real life by parents who are successful with GFCF. Other problems with the study include the following –

  • The 4-6 week period might be too short.
  • The sample is skewed – kids who might be expected to show the most benefit were excluded.
  • The sample size is too small to mean much.
  • Allowing soy may have compromised the results.
  • The study did not screen for many common food allergies and hypersensitivities, nor remove these allergy triggers from the kids’ diets.
  • The study did not screen for other known food causes of hyperactivity nor remove these from the kids’ diets.
  • The study does not measure medical measures of benefit.

A detailed discussion of these issues follows. The bottom line is that in this case, “an absence of evidence is not evidence of absence.” The study shows an absence of evidence about the benefits of GFCF, which is probably due to its many problems with study method and participant selection. It does not establish evidence that benefit is absent.

Concerns about study method, participants & outcome measures

The study admits that the 4-6 week period might be too short. The trial period of 4-6 weeks is based on findings from patients with gastrointestinal (GI) issues. This study excluded participants with known GI issues, so the 4-6 week trial period seems arbitrary and possibly too short. Even within this short study period, as many as 20 dietary infractions were recorded. As the study admits, if this period was indeed too short, then it compromises the results.

The sample is skewed – because kids who might be expected to show the most benefit were excluded. The study excludes all children who might have been expected to show the strongest positive reactions to GFCF in the study’s short timeframe – such as children with gastrointestinal issues.

The sample size is too small to mean much. The study only enrolled 14 kids. As study acknowledges – “the small sample size limits interpretation and generalizability of findings.”

The study acknowledges that allowing soy may compromise the results. According to the study, one concern with its design is that “… some investigators place equal importance on removing soy.”1 Here’s why –

  • Soy proteins have known cross-reactivity with bovine casein proteins2.
  • Soy, as well as other top IgE allergens can contribute to hyperactivity and irritability in children with autism3.

For these reasons, parents who have seen results from GFCF also remove soy from the diet. Unlike these parents, the study allowed soy – and acknowledges that this may have compromised the results.

The study did not screen for the most common food allergies. Nor did it remove these allergy triggers from the kids’ diets.

Food allergies are estimated to affect 9% of children aged 3-5 years and over 30% of these children have multiple food allergies4. Allergic reactions can cause neuropsychiatric symptoms, such as irritability and hyperactivity. Moreover, the discomfort and pain associated with allergic diseases can aggravate behavioral symptoms in ASD children.  In this study, participants were tested for allergies to milk, wheat, eggs and corn. However –

  • The study did not test for allergies to soy, peanuts (the #1 allergy in terms of prevalence), tree nuts, shellfish and other food proteins that are common allergens. Nor is there any mention of excluding these allergy triggers from the GFCF diet given to the study participants.
  • Similarly, the study design did not screen for non-IgE mediated hypersensitivities5 to food proteins, including soy.

These confounding factors probably contributed to the lack of evidence that the diet is helpful.

The study did not screen for known food causes of hyperactivity nor remove these triggers from the kids’ diets.

Hyperactivity caused by food colors has been noted in the literature in numerous studies6 as well as anecdotally by parents. Similarly, food reactions to additives and preservatives like sulfites have been reported in the literature as well as anecdotally by parents. Therefore, parents who are successful with the GFCF diet typically use homemade food free of food colors, additives and preservatives. The study does not screen for these known causes of hyperactivity, nor does it factor these concerns into the diet given to the kids in the study.

The study does not measure medical measures of benefit.

The study focuses only on overt, clinically obvious behavioral measures that show up within 4 weeks or so. It lacks before-and-after lab testing for improvements in immune or metabolic parameters that may be more gradual, and take time to manifest in terms of improved behaviors. For example, the study did not look at lab testing such as –

    • Standard measures of inflammation
    • Standard measures of gut health on blood tests and stool tests
    • Changes in gut flora
    • Changes in immune markers7

References

  1. Mathews (2008) “Nourishing Hope for Children with Autism: Nutrition and Diet Guide for Healing Our Children.”
  2. Curciarello (2014) “Targeting a cross-reactive Gly m 5 soy peptide as responsible for hypersensitivity reactions in a milk allergy mouse model” http://www.ncbi.nlm.nih.gov/pubmed/24416141
  3. Jyonouchi (2010) “Autism spectrum disorders and allergy: observation from a pediatric allergy/immunology clinic.” http://www.ncbi.nlm.nih.gov/pubmed/20441426
  4. Allergy Statistics, American Academy of Allergy, Asthma and Immunology http://www.aaaai.org/about-the-aaaai/newsroom/allergy-statistics.aspx
  5. Spergel (2006) “Nonimmunoglobulin E-Mediated Immune Reactions to Foods” http://www.aacijournal.com/content/2/2/78
  6. Schab (2004) “Do artificial food colors promote hyperactivity in children with hyperactive syndromes? A meta-analysis of double-blind placebo-controlled trials” http://www.ncbi.nlm.nih.gov/pubmed/15613992
  7. Jyonouchi (2005) “Evaluation of an association between gastrointestinal symptoms and cytokine production against common dietary proteins in children with autism spectrum disorders” http://www.ncbi.nlm.nih.gov/pubmed/15870662

2 Comments Add yours

  1. Alejandro says:

    Nicely done Gita! Thanks.

  2. jay k says:

    If you take 14 kids with NO medical issues…. of COURSE they will have no response to a GFCF diet. This is ridiculous and an absolute slap in the face to diligent research.

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