What is the autism diet?

Actress Jenny McCarthy claims that her son Evan is recovering from autism, in part due to a special restricted diet.
Jordan Strauss/WireImage

Autism is a medical mystery -- and a highly controversial one at that. The debilitating disorder makes headlines in the news on a frequent basis, and not too long ago, it was getting press in the talk-show circuit, courtesy of actress Jenny McCarthy. McCarthy garnered attention for the disorder when she asserted that ingredients in some childhood vaccines may trigger the development of disorders on the autism spectrum (abbreviated as simply "autism" from here on out). So far, no reputable scientific study has established a connection between vaccines and autism, and removal of the ingredient theorized to be the culprit -- a preservative called thimerosal -- hasn't caused diagnosis rates to go down. Regardless of what researchers believe triggers autism, with 1 in 110 children in the United States living with the disorder (and annual increases in diagnosis), it's no wonder that the race is on to determine the cause or causes [source: CDC].

And this isn't the only controversy surrounding autism. Specialists also disagree on how to treat the disorder. Most children with autism receive some type of behavioral therapy, but they might also take medications or receive complementary therapies. McCarthy and other proponents of a special diet for autistic children claim that by changing what a child eats, you can improve his or her behavior, speech or both.


Autism is a neurological disorder, so it might seem strange that it could be affected by what's going on in the gut. However, more and more researchers are exploring the idea that some physical issues common to children with autism may be related to the symptoms they experience. According to Dr. Martha Herbert, a pediatric neurologist at Harvard, "so many autistic kids have a history of food and airborne allergies [...] or eczema, or diarrhea" [source: Neimark]. What if treating these physical issues could improve the behavioral symptoms of autism? That's the basis of the autism diet.

Like many other treatments, the autism diet isn't scientifically proven to improve symptoms or help children recover from autism. So far, there's only anecdotal evidence from parents of autistic children, which isn't enough to establish whether the diet really works. The diet usually requires excluding gluten (a protein found in wheat) or casein (a protein found in milk). Let's start with looking at why these substances -- found in so many foods and other products -- might exacerbate the symptoms of autism.


Food Allergies and Leaky Gut Syndrome

Some believe that an overgrowth of the yeast Candida albicans (which naturally occurs in the body) can damage the intestines of children with autism.
Photo courtesy CDC/Dr. William Kaplan

There are a couple of different theories as to why children with autism can benefit from a diet free from gluten and casein. One draws a connection between food allergies and behavioral problems. An allergy is essentially an extreme inflammatory response by the immune system to a substance that it sees as an invader. Allergies can manifest in a wide variety of physical symptoms, including diarrhea, vomiting, hives, wheezing and rashes.

Children with autism often have trouble communicating, so they may not be able to tell their parents that they're experiencing painful symptoms like acid reflux and stomach cramps. Instead, they scream, act aggressively and throw temper tantrums. The discomfort, pain and other physical reactions from the allergic response could trigger autistic behaviors.


­Another theory states that many children with autism have a "leaky gut," also known as increased intestinal permeability. This theory suggests that autistic children have tears and holes in their intestinal walls, possibly due to damage from toxins, antibiotic sensitivity or infections (such as an overgrowth of the yeast Candida albicans). In addition, these children may lose healthy digestive bacteria and have damage to the cells that produce enzymes needed to absorb certain proteins (such as gluten) properly.

Both leaky gut and problems with absorbing specific proteins, the theory goes, can cause intestinal contents to enter the bloodstream. This not only includes toxins and bad bacteria, but also protein molecules that haven't been fully digested. The latter may actually lead to food allergies because the immune system treats the molecules as foreign matter. It can also lead to what some autism researchers call the opioid effect.

Proponents of the leaky gut theory believe that the partially digested protein molecules from gluten and casein, also known as peptides, can reach the brain via the bloodstream. Peptides have a molecular structure similar to that of your brain's natural opioids (endorphins), so they're drawn to the brain's opioid receptors. This leads to problems with behavior, speech and social skills. Just as opioid drugs such as heroin are addictive, so are foods high in gluten and casein for children with leaky gut.

Some autism researchers have tested the urine of these children and found high levels of these peptides, which seem to support the leaky gut syndrome theory. Researcher Dr. Paul Shattock has drawn a connection between escalating levels of peptides and the most severely impaired autistic children [aource: McCandless]. However, a March 2008 study published in the Archives of Diseases in Childhood by British researchers found that children with autism didn't have a higher level of peptides than those who did not have the disorder.

Many doctors don't believe that leaky gut syndrome exists. Some children with autism do have food allergies when tested, but not all. But for their parents, some don't mind that there's not science-based evidence to back up the autism diet. What matters is that it worked for their child. We'll look at exactly what a gluten-free/casein-free (GFCF) diet entails, as well as avoiding salicylates and other foods, next.


Gluten-free, Casein-free Diet

Gluten turns up in the most unlikely places. In 2006, McDonald's was sued because it hadn't informed the public that gluten and casein were used to make its french fries.
Scott Olson/Getty Images

A 2008 survey conducted by the Autism Research Institute showed that out of the 2,500 cases in which a gluten-free, casein-free (GFCF) diet was used in the treatment of autism, 66 percent of children showed improvement. Fifty-two percent of the more than 6,300 cases in which parents just eliminated casein also got better. However, not all children with autism experience benefits from special diets.

It's pretty challenging to avoid all gluten and casein, and it's important to discuss any dietary changes with a doctor. Most parents begin with removing casein, which is easier to do. Going on the full GFCF diet is generally a slow process that involves eliminating one food at a time, and most believe that the child should be casein-free for about a month to see if there are improvements. Once gluten is removed, the trial period should last at least four months.


Removing all casein and gluten from a child's diet means paying a lot of attention to ingredient lists. The obvious foods containing casein include milk, all forms of cheese, yogurt, ice cream and butter. However, it can also be found in cookies, hot dogs, vitamins, cream soups and salad dressing. If the ingredient list includes casein, caseinate, sodium caseinate, lactose or whey, then it's not allowed on a casein-free diet.

Gluten is even more prevalent. In addition to being in anything made with wheat (bread, crackers, baked goods, pasta), it can also be found in other grains, such as rye, barley and oats. Soy sauce contains gluten, and so do hot dogs, lunch meats, seasonings and spices, licorice, tea (if the tea bags are sealed with wheat paste) and a host of other prepackaged foods. Gluten is even used in nonfood items like toothpaste, lip balm and lotion, so parents must read those labels, too. Those who have gotten positive results from the diet stress the importance of eliminating all casein and gluten and claim that accidental slip-ups have resulted in a return of autism behaviors.

So what do children on GFCF diets eat? There are lots of gluten-free foods available in grocery stores and health-food stores due to the numbers of people with celiac disease, an autoimmune disorder affecting the small intestine that results from a reaction to a specific type of gluten. Most children on these diets eat a lot of lean protein, fruits and vegetables.

Although the GFCF diet is the most common autism diet, some parents take it a step further and remove other foods as well. Those who believe that yeast overgrowth can cause autistic behavior restrict sugar intake because sugar is food for yeast and encourages its growth. The yeast-free diet prohibits any fermented foods (such as vinegar) as well as any foods that may contain molds, like mushrooms.

Other diets may remove artificial colorings, flavorings and preservatives because they can contain salicylates, a plant compound also found in some fruits. The connection between artificial colorings, flavorings and preservatives and behavior disorders isn't new; a similar diet has been used to treat children with ­ADHD since 1979 (and has also been controversial).

For a more in-depth look at autism, related disorders and the issues surrounding it, try the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Autism Information Center: Centers for Disease Control and Prevention http://www.cdc.gov/ncbddd/autism/index.html
  • Autism is Treatable: Autism Research Institutehttp://www.autism.com/treatable/index.htm
  • GFCF Diethttp://www.gfcfdiet.com
  • Kirk, Sally. "Hope for the Autism Spectrum." Jessica Kingley Publishers, 2008.
  • Neimark, Jill. "Understanding Autism: The Answer May Lie in the Gut, Not in the Head." Discover Magazine, April 2007.
  • McCandless, Jacqueline. "Children with Starving Brains." Bramble Books, 2007.
  • McCarthy, Jenny and Jim Carrey. "My Son's Recovery From Autism." CNN.com, April 4, 2008.http://www.cnn.com/2008/US/04/02/mccarthy.autsimtreatment/index.html
  • "Research Focuses On Which Foods May Affect Autistic Behavior." ScienceDaily, August 9, 2008.http://www.sciencedaily.com­ /releases/2008/08/080807175440.htm