House CallDec/Jan 2014 Issue

Research Roundup: Rice is Safe, Intestinal Permeability, & More!

The latest medical news for people with allergies and food sensitivities.

Photo © Ufo/Rf/Amana Images/CORBIS

Rice is Safe

A new FDA-led study is easing concerns raised in recent years about arsenic levels in rice. Between 2012 and 2013, the agency tested 1,300 samples of rice and rice products for both total and inorganic arsenic levels, the most toxic form. Scientists determined that while levels varied—more processed forms like instant rice had lower levels than whole grain brown rice—they were too low to pose immediate or short-term health risks.

Many foods contain trace amounts of arsenic since the chemical element occurs naturally in soil and water. Rice soaks up more arsenic than most other crops, in part because it’s grown in water.

FDA has monitored arsenic levels in rice and other foods since 1991. However, new analytic tools now provide greater specificity about the different types of arsenic present in foods. The agency will use these new tools to study long-term exposure to very low levels of arsenic in rice and rice products.

Meantime, FDA stresses that consumers should eat a well-balanced diet and avoid overexposure to any one food. In addition to rice, gluten-free grains include amaranth, buckwheat, millet, quinoa, sorghum and teff.

Intestinal Permeability in Food Allergy

In over a third of food-allergic children, the gut wall is excessively permeable, according to a new study led by researchers at Albany Medical College in New York. Researchers determined whether the gut wall was too permeable by measuring the output of two sugars in the urine of 131 children with milk and egg allergies.

Because the children had been avoiding their trigger foods—milk or egg—and were symptom free, researchers suspect this permeability wasn’t the result of a recent allergic insult. (During an allergic reaction, inflammatory factors can cause injury to the gut lining.) Instead, they call it a “baseline defect.” However, the study didn’t demonstrate whether increased permeability was the cause for their food allergy, says lead author, Kirsi Jarvinen, MD.

Other studies have documented increased gut permeability in those with food allergy but this is the largest such study. Future research may help clarify whether this increased permeability is a cause or a consequence of food allergy. It may also elucidate why, in the new study, those food-allergic children with permeable gut walls were also shorter in stature than their food-allergic peers with intact gut walls.

The gut wall regulates what food proteins (and other molecules) enter the circulation. This, in turn, affects the ability of food proteins to trigger a systemic immune response.

The study was published online in August in Pediatric Allergy and Immunology.

Allergy Treatment Needs Work

The first long-term study of milk-allergic children treated with oral immunotherapy has yielded some disappointing results. Oral immunotherapy involves giving tiny, gradually increasing amounts of an allergic food to “teach” the immune system to ignore the food. Still considered experimental, the treatment should only be performed under careful medical supervision or in a research setting, due to the risks involved.

In the new study, researchers at Johns Hopkins Children’s Center followed 32 milk-allergic children who’d been given oral immunotherapy for an additional three to five years after treatment. At the end of the original treatment period, all but three of these children were able to consume at least some milk in their diet. But over the long term, just 8 children (25 percent) remained symptom free. Twelve children (38 percent) had frequent symptoms with milk consumption and an alarming six children (19 percent) suffered at least one episode of milk-induced anaphylaxis.

Researchers say the findings underscore that oral immunotherapy is “far from ready” for mainstream use and that more research on long-term outcomes is needed.

The study was published in June in the Journal of Allergy and Clinical Immunology.

Worse Asthma with Food Allergy

Twenty-four percent of urban school-age children with asthma also have a physician-diagnosed food allergy, according to a new study led by researchers from Boston Children’s Hospital. They investigated the relationship between asthma and food allergy in 302 asthmatic children from 20 inner-city schools.

Asthmatic children with food allergy had worse asthma; they were twice as likely to suffer daytime symptoms and twice as likely to use an asthma controller medication than their peers without food allergy. They were also twice as likely to have been hospitalized. Those with multiple food allergies had five times the rate of hospitalizations, more daytime symptoms and more unscheduled visits to the doctor for asthma symptoms. Greater asthma surveillance may be required in food-allergic children, the researchers write.

The study was published online in August in the Journal of Allergy and Clinical Immunology.

Healthy Diet Reduces Food Allergy Risk

Two-year-olds without food allergy ate significantly more fruits, veggies and home-prepared foods than their food-allergic counterparts, according to a research team from the University of Southampton in the UK. Investigators there collected food diaries from the parents of 1,140 toddlers, homing in on the diaries of 41 who received a diagnosis of food allergy during the study period. The diaries of 82 toddlers without food allergy were used for comparison.

The study is the first to suggest that overall diet composition may be an important factor in the development of food allergy. Other studies have focused on specific foods or variables, like the timing of solid food introductions. These may be an oversimplification of the complex interactions taking place, the researchers write. A number of nutritional and dietary variables might be acting on the development of food allergy in infants and toddlers, they add.

More studies are needed to confirm the new finding; it’s too early to recommend a healthy diet specifically aimed at food allergy prevention. However, there’s no risk in advocating a childhood diet rich in fresh fruits and vegetables and unprocessed foods.

The study was published online in July in the Journal of Allergy and Clinical Immunology.

Head Trauma and Celiac

In 2009, Living Without covered the story of a teen seriously injured in a jet-ski accident. Several months later, she developed celiac-like symptoms and soon thereafter was diagnosed with celiac disease. At the time, consensus from the medical experts was that while trauma itself is unlikely to trigger celiac disease, increased medical attention in the months following an accident could lead to the detection of previously undiagnosed celiac disease.

Now a new study suggests there may, in fact, be a small increased risk of developing celiac disease following head trauma. In the study, those with celiac disease were 10 percent more likely to report an earlier head trauma than those without it. The first year after trauma was associated with the highest risk of a celiac diagnosis.

It’s possible heightened medical surveillance may explain the finding. Or, say researchers, head trauma could set off an autoimmune reaction against an enzyme in the brain, tissue transglutaminase 6 (TG6), which is closely related to a key player in celiac disease, tissue transglutaminase 2 (TG2). In either case, trauma could only trigger celiac disease in those with the genetic predisposition for it.

Conducted at the Karolinska Institute in Sweden, the research involved a nationwide sample of 29,096 people with celiac disease and 144,522 without it. The study was published in August in BMC Neurology.

Antibiotics and Celiac Disease

Researchers from the Karolinska Institute in Sweden have linked antibiotic use with the onset of celiac disease. The study is the first to make such a connection. Investigators used data from a Swedish drug registry to compare antibiotic use in 2,933 Swedes with celiac disease and 28,262 without the autoimmune disorder.

Those with celiac disease were much more likely to have used antibiotics in the year before their diagnosis than those without it (25 percent versus 19 percent). They were also more likely to have used multiple courses of antibiotics. When researchers looked at a subset of individuals whom they dubbed “early celiacs” (i.e., they had celiac antibodies or intestinal inflammation but not the hallmark flattening of the intestinal villi), they also found a higher likelihood of recent antibiotic use.

Antibiotics may significantly change the gut environment, which may play a role in the development of celiac disease, say researchers. However, it’s hard to know exactly when celiac disease starts. It’s also possible the antibiotics may have been prescribed for symptoms related to undiagnosed celiac disease. More research is needed to tease apart these issues.

The study was published in July in BMC Gastroenterology.

Reason to Repeat a Celiac Biopsy

Doctors used to perform a follow-up intestinal biopsy after a celiac patient was on the gluten-free diet for a time in order to confirm intestinal healing. But since the development of more reliable blood testing, this practice has become less common.

Now a new study from the Celiac Disease Center at Columbia University has found the repeat biopsy can provide useful information about a patient’s risk of lymphoma, an uncommon but serious cancer linked with celiac disease.

Lymphoma risk is not equally distributed among all patients with celiac disease, explains study author Benjamin Lebwohl, MD, in an interview with the National Foundation for Celiac Awareness. Those patients whose intestinal villi had healed at the follow-up biopsy had a significantly lower risk of lymphoma, approaching that of the general population, while those with persistent villous atrophy had nearly four times the risk. (The overall incidence of lymphoma was still low in all groups of celiac patients.)

Practice guidelines don’t mandate a routine follow-up biopsy but the new study provides strong rationale for it, in part because blood testing isn’t perfect; results can be normal despite ongoing intestinal damage. Lebwohl considers repeating the biopsy in his celiac patients approximately two years after they start the gluten-free diet.

This research looked at 7,625 celiac patients in Sweden who had follow-up biopsies performed between six months and five years after their initial biopsy. The study was published in August in the Annals of Internal Medicine.

Senior medical correspondent Christine Boyd lives in Baltimore.

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