A recent article from NBC News discusses a new study published in the Journal of the American Medical Association that suggests BPA exposure may contribute to obesity in children. The study measured levels of BPA in the urine of nearly 3,000 children and teens, and found that kids with higher levels were 2.6 times more likely to be obese compared with kids exhibiting lower levels of BPA in their urine.
The researchers noted that BPA in the urine was associated with the possibility of obesity in children regardless of the amount of calories they consumed, which led them to hypothesize that something happens to their metabolisms. Some experimental studies have shown that BPA increases the size of fat cells and can inhibit a hormone involved in lowering the risk of heart disease. In addition, BPA may disrupt estrogen and testosterone balance, which can adversely affect caloric balance.
Manufacturers use BPA to line the inside of cans to prevent metals from leaching into foods and to prevent foods from having a metallic taste. The Food and Drug Administration has banned the use of BPA in some products including baby bottles and sippy cups, but has indicated the need for more research because of “some concern about the potential effects of BPA on the brain, behavior and prostate glands of fetuses, infants, and children.”
Experts not affiliated with the research believe the study was carefully conducted, but caution that it is only one study and more research is needed to conclusively link BPA exposure to obesity. In addition, experts feel that the study may lead parents to stop buying canned fruits and vegetables altogether, thereby limiting nutritious options especially among low-income populations.
To better understand the significance of this study, we enlisted the help of Dr. Bruce Chassy, professor of food microbiology and nutritional sciences with the University of Illinois who previously provided Best Food Facts with information regarding the effects of exposure to BPA on human health, and Dr. Carl Winter, a food toxicologist with the University of California-Davis.
Dr. Bruce Chassy
Dr. Chassy: “This is one study that has not been corroborated or repeated and as such should be considered no more than an interesting observation that may merit watching the follow-up research and analysis. I say ‘may’ because there is no obvious mechanism one can think of that should associate BPA in urine in children with obesity unless it is the obvious one that obese children consumer greater amounts of food and beverages.”
“We do consume tiny amounts of BPA every day at levels far below those that would be expected to do harm. It just may be the levels of excreted BPA and its metabolites are higher in obese children because they consume more and therefore excrete more. It is important to note that none of this speaks to harm since these levels are far below those which would be considered harmful. As we like to say, the dose makes the poison.”
Dr. Chassy points out several issues with the study:
- No cause and effect relationship was shown between BPA and obesity.
- The effect was noted only in Caucasian children, which is difficult to explain and may indicate the finding is the result of random variation.
- A single urine sample is like a snapshot in time, and there is no way of knowing whether the same results would have been seen by repeated testing over a longer period of time.
- If the result itself is reproducible, it could easily be that the higher levels were a by-product of overweight conditions and the lifestyle associated with obesity rather than a cause.
Dr. Chassy: “It has become stylish in some circles to blame every malady imaginable on the chemical that is currently in the news and under scrutiny. Part of this occurs because scientists have a natural curiosity. If claims are made about a chemical doing liver damage and they study obesity, it is logical to see if a chemical has an impact on obesity. These odd associations are also found because scientists can get grants to study chemicals of current interest.”
Dr. Carl Winter
Dr. Winter: “The results in this paper are similar to one published by Lang, et al in 2008. As is typical with epidemiological studies, results suggest a correlation between BPA urinary excretion and obesity in children, but do not represent a cause-and-effect relationship. One could equally well relate the apparent difference in metabolic activity in obese children with the unique ability to metabolize BPA more rapidly than non-obese children, resulting in higher levels of BPA urinary metabolites. (The causation here would be that obese people are more likely to quickly metabolize BPA.)”
“More appropriately, we still need to consider the amount of BPA exposure rather than epidemiological correlations in determining safety. Health Canada recently came out with a conclusion that BPA exposure from food packaging is not expected to pose a health risk.”
“So from my perspective, it is quite a stretch to go from the conclusion that urinary BPA levels and obesity are correlated to the conclusion that BPA causes obesity. It would be nice to have these relationships examined more closely through more science, but it is much too early to make any cause/effect conclusions.”