SAN DIEGO – Could increased consumption of phytoestrogens help prevent or treat asthma and allergy?
Dr. Jessica Savage, an allergist and immunologist at Brigham and Women’s Hospital, Boston, and her colleagues correlated one-time urinary phytoestrogen measurements from 7,909 subjects in the National Health and Nutrition Examination Survey, 2003-2010, with histories of physician-diagnosed asthma and self-reported wheezing.
Dr. Jessica Savage
The investigators also considered serum total and specific IgE levels obtained from a subset of 2,218 subjects. They defined atopy as having at least one positive IgE level (0.35 kU/L or above) to an aeroallergen.
Adjusting for a wide range of potential cofounders, including age, gender, race, urinary creatinine, poverty, body mass index, smoking, and smoke exposure, they found that, for every natural log increase in urinary enterolactone, the odds of asthma decreased by 8%.
Enterolactone also was significantly inversely associated with asthma prevalence and had the strongest inverse association with wheezing.
For every natural log increase in urinary o-desmethylangolensin (ODMA), there was a 7% decrease in the odds of wheeze. The odds of atopy significantly decreased with increasing ODMA levels.
"We can’t say anything about cause and effect" yet, but if the association holds up with further investigation, it might suggest a role for phytoestrogen probiotics to help treat the conditions, Dr. Savage said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
Phytoestrogens are plant-derived compounds. Gut bacteria convert lignans, which are particularly plentiful in flax seeds, into enterolactone, and the isoflavone daidzein, particularly plentiful in soybeans, into ODMA.
"Increased consumption of sources of phytoestrogens or probiotics to increase precursor conversion may help prevent or treat asthma and allergic disease," Dr. Savage said. "I was really surprised that the enterolactone signal is very strong both for asthma and for wheezing."
Although soy-derived compounds have been associated with better lung function and decreased lung symptoms in the past, "there’s really not a lot known about enterolactone," she said. "The idea is that somehow these metabolites are anti-inflammatory. Urinary levels are partly due to your diet and partly to having the right bacterial flora in your gut. Our findings could be explained by people just having different diets; they could also be explained by people with asthma having lower levels of the right kind of bacteria."
About half the subjects were female, and about 80% were over age 18 years; 70% of the study population was white. Enterolactone tertiles were defined as 0.2-178; 179-644; and 645-122,000 ng/mL urine. ODMA tertiles were defined as 0.1-1.4; 1.5-12.8; and 12.9-18,500 ng/mL urine.
The study was funded by the National Institutes of Health. The investigators reported having no disclosures.
Dr. Jennifer Cox, FCCP, comments: It is a novel idea that phytoestrogens could prevent or treat allergy and asthma. However,the this study population had few pediatric subjects, the majority of patients were white, and it was a one-time measurement. Before we recommend to our patients to increase consumption of phytoestrogens, further research to include pediatric patients, a more diverse ethnic background, and frequent monitoring of urinary levels will be helpful to document if there is a true cause and effect.