Are Dietary Supplements to Blame for Allergies and Asthma?
Recent data have shown that the prevalence of asthma and allergic diseases is again on the rise—and many scientists suspect that dietary changes may partially explain this uptick.
Augusto A. Litonjua, MD, MPH, and Sunita Sharma, MD, MPH, both of Brigham & Women’s Hospital and Harvard Medical School in Boston, conducted a review of the existing literature to look specifically at the effects of folic acid and other B vitamins on the development and worsening of asthma and allergies.
There have only been a few small trials to date with regard to folic acid and methyl donors, but as a whole, they found a considerable amount of conflicting evidence.
One reason for this lack of definitive results is “that the role of diet in the development of atopy is complex, difficult to measure, and limited by a dearth of interventional trials,” the authors write in their review, which appears in the May issue of the Journal of Allergy and Clinical Immunology.
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“A murine model of asthma showed that offspring mice from mothers who were fed a diet rich in folate and methyl donors developed features that could be interpreted as asthma-like,” Litonjua says. “However, human studies that have investigated the amount of folic acid and methyl donors in the diet have not shown definitive results.”
Although differences in study design partially explain the varied findings, the researchers identified two issues that have been largely overlooked in these studies and need further investigation:
• It appears that methyl donor nutrients affect one of many pathways and occur in many of the same foods, suggesting there may be interrelationships.
• It is becoming clear that the human intestinal microbiome is involved in the metabolism and production of B vitamins and other methyl donor nutrients.
“We feel that asthma and allergies are disorders for which there are multiple causes—genetic, behavioral (lifestyle), and environmental,” Litonjua says. “Thus, in Western populations that are generally nutritionally replete, supplementation of single nutrients may not add much on a population level. The story may be different in countries where malnutrition is rampant.”
He and Sharma are currently conducting a trial to determine if vitamin D supplementation could play a role in asthma prevention. “We think vitamin D is different from these other vitamins and nutrients because most populations have insufficient vitamin D,” he says.
As for patients who are currently taking supplements to combat their asthma and allergies, Litonjua suggests primary care providers let them know that current research doesn’t support dietary supplements designed to boost the levels of single nutrients.
“(However), in many cases, patients have already made up their minds to take these supplements even before coming to their primary care providers,” Litonjua says. “If they insist on taking supplements, then the role of the primary care provider is to make sure that they are not taking more than the recommended amounts of these supplements.” He also recommends reiterating the value of a healthy diet and exercise regimen.
—Colleen Mullarkey
Reference
Sharma S, Litonjua A. Asthma, allergy, and responses to methyl donor supplements and nutrients. J Allergy Clin Immunol. 2014 May;133(5):1246-54.