Q: I read not so long ago that BPA may cause childhood obesity. Can you tell me if that is true and what should I do to limit my child's exposure to BPA?
A: BPA is the abbreviation for Bisphenol A, a breakdown product of coatings that prevent metal corrosion in food and beverage containers. It is used to manufacture polycarbonate resins. For a number of years, experts have become increasingly concerned that it may be unhealthy - especially to the very young. BPA was banned from baby bottles and sippy cups a few years ago.
However this chemical is still found in canned foods, some food packaging and polycarbonated-bottled liquids.
In a study published in the Journal of the American Medical Association on Sept. 9 researchers from the New York University School of Medicine found a significant association between BPA concentrations and obesity. The study was the first of its kind in children, making it a provocative and perhaps a landmark study.
It involved 2,838 participants between the ages of six and 19 years and subjects were randomly chosen, nationwide. The study was conducted between 2003 and 2008. The authors specifically looked at the urinary concentrations of BPA and obesity prevalence. (BPA in the urine does not rapidly decline with fasting time).
After controlling for the many other variables which contribute to obesity, such as race, ethnicity, age, caregiver education, poverty-to-income ratios, gender, caloric intake and television watching, the authors concluded that urinary BPA was significantly associated with obesity in children and adolescents.
The study specifically looked at obesity by using statistical methods and the body mass index (BMI z score) and did not research the association with being overweight. Typically obesity refers to a child whose BMI exceeds the 95th percentile while overweight refers to a child whose BMI is between the 85th and 95th percentile.
The study also looked at other chemicals and found that obesity was not associated with other environmental chemicals commonly used in consumer products such as soaps and sunscreens.
I have been the pediatrician at the Calgary Pediatric Weight Clinic for the past eight years and it has been my honour to help children reach their healthy weights for more than a few decades. When I see studies like this, and hear other experts debate it, I cannot help but wonder if the smoke indeed indicates there may be a fire. There may be an association, but it is too early to say it is a cause. We must remind ourselves that this was the first study in children.
In adults the association between BPA exposure and adult diabetes, cardiovascular diagnoses and abnormal liver functioning has been published previously. Most of the BPA children are exposed to come from dietary sources. After exposure, BPA gets stored in fat tissue and researchers call the relationship between BPA exposure and urinary BPA concentrations "complex."
Data in the U.S. suggest associations between urinary BPA and consumptions of sodas in cans, school lunches and meals prepared outside the home, but not bottled water or canned tuna.
We are not sure if the timing of the exposure matters. It may be that earlier exposure sets the stage. It may be that there are also different responses to BPA based on genetic or epigenomic characteristics. In the New York study published a few weeks ago, among white children the association between urinary BPA and obesity was particularly strong and significant. Estrogen levels in males are associated with obesity and BPA has a mild estrogenic effect, increasing the estrogen levels in males.
The fact that BPA was banned from baby bottles and sippy cups is significant. Turtles don't end up on posts on their own and banning BPA exposure to babies and toddlers did not just happen overnight.
Much research and debating preceded that decision - which in fact took place in Canada before it took place in the U.S. Last year the FDA declined to ban BPA in aluminum cans and other food packaging, but they noted that "we will take reasonable steps to reduce human exposure to BPA in the human food supply and continue to consider evidence on the safety of the chemical."
My advice for now to the patients I see in the Pediat-ric Weight Clinic and in my community-based office is to be aware of this study. It is a start. As the authors themselves admit, there are limitations and we are not yet 100 per cent sure how exactly BPA may play a role, if at all.
Dr. Nieman is community pediatrician and the founder of www.healthykids.ca. He is a marathon runner and has completed 82 marathons thus far. He is the president of the Alberta Chapter of the American Academy of Pediatrics. Dr. Nieman posts resources on twitter @drpeternieman
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