September 17, 2008
New Study Links Heart Disease to Bisphenol A Past Research Showed Chemical’s Effects on Infants
By JOHN FAUBER
Adults with higher levels of the common chemical bisphenol A in their urine had significantly increased risk of heart disease, diabetes and liver abnormalities, according to the first large study of human exposure to the substance.
And while animal research had suggested a possible diabetes and obesity risk in humans, the heart disease finding was somewhat unexpected, though the chemical is present in more than 90% of people.
The study did not find any statistically significant increased risk of cancer, arthritis, respiratory disease or stroke, although the lead author said it was not adequately designed to look for cancer risk.
The research, which was released online Tuesday, is likely to fire up the debate over the chemical, which is used in baby bottles and to line food and beverage containers, and may provide more ammunition for those who feel the substance should be banned in some products.
On the one hand, the study raises new concerns about the chemical, including in adults exposed to low levels. However, the methodology used in the research is not definitive and the study did not provide proof that bisphenol A was the cause of the increased disease risk.
"A lot of the concern about BPA until now has centered on children," said lead author Iain Lang, an epidemiologist and researcher at Peninsula Medical School in Exeter, England. "Our research group is concerned with health and disease in middle-aged and older people."
Those in the study, men and women aged 18 to 74, were divided into four groups based on the levels of bisphenol A in their urine.
Almost 3 times higher
Those with the largest amount of the chemical in their urine were 2.9 times more likely to have cardiovascular disease than those in the bottom group. For diabetes, the risk was 2.4 times greater. Higher levels of the chemical also were associated with higher concentrations of abnormal liver enzymes, a sign of potential liver toxicity.
The researchers noted that the amount of bisphenol A found in the study subjects was much lower than what generally is considered safe, about 3,250 micrograms a day for a 143-pound adult.
For instance, those in the top quarter of the study had bisphenol A exposure levels of about 50 micrograms a day, compared with those in the lowest quarter, about 10 micrograms a day.
"This is the most important study on bisphenol A published to date," said Shanna Swan, an epidemiologist and professor in the department of obstetrics and gynecology at the University of Rochester School of Medicine and Dentistry in New York.
She said its findings are consistent with the large amount of laboratory and animal research that already has been compiled.
Swan, who was not a part of the study, said the findings now will make it impossible for the U.S. Food and Drug Administration to conclude that bisphenol A is safe for humans. An FDA committee on bisphenol A held a hearing Tuesday on the use of the chemical in food and beverage containers.
And since the study found increased disease risk in adults who were exposed to low levels of the chemical, it suggests that the potential adverse effects on children and fetuses is even more concerning, said Swan, who does research on how so-called endocrine disruptors -- environmental agents that mimic hormones -- affect human growth and development.
An analysis late last year by the Journal Sentinel reviewed 258 scientific studies of bisphenol A. An overwhelming majority of those studies showed the chemical is harmful -- causing breast cancer, testicular cancer, diabetes, hyperactivity, obesity, low sperm counts, miscarriage and a host of other reproductive failures in laboratory animals.
Study has limitations
However, the American Chemistry Council said the JAMA study has design flaws and significant limitations.
For instance, the study does not make a distinction between Type 2 diabetes and Type 1, which is believed to be more likely caused by genetic factors, the council said.
"While properly designed and executed statistical studies on this and other compounds can bring valuable new insights with respect to human health, sometimes they do not, and sometimes they merely claim 'false associations' that add little to and even confuse the body of science," the council said in a statement.
Indeed, the study does not prove cause and effect, it only shows an association between bisphenol A levels in urine samples and various self-reported diseases.
Such association studies can fail to find possible confounding factors.
For instance, it's possible that people who eat a lot of junk food and other unhealthy processed foods are exposed to higher levels of bisphenol A because of food packaging.
It could be that it is the junk food and not the bisphenol A that is causing their heart disease, said Michael Widlansky, an assistant professor of medicine and pharmacology at the Medical College of Wisconsin in Wauwatosa.
"You have to be careful about reading causal implications into this," said Widlansky, a cardiologist who practices at Froedtert Hospital.
He noted that years ago, animal and epidemiological studies suggested that hormone replacement therapy protected women against cardiovascular disease, but when rigorous studies were done, the opposite was found.
He said caution is needed in deciding to ban bisphenol A.
"We don't want to switch to something that is just as bad," he said.
Calls for ban
Still, the study suggests there is a potential for health problems, and if it were to be confirmed by another large study, that could be enough to consider removing the chemical from food packaging, he said.
Lead author Lang said the study alone is not enough to warrant a ban on the chemical's use in food packaging. He said replicating it with other groups of people still needs to be done, including understanding more about how bisphenol A acts in people.
However, others who have researched the chemical say there already was plenty of evidence to support a ban prior to the JAMA study.
Just last month, a separate study offered a possible clue as to how the chemical might increase heart disease risk.
Using fat tissue removed from people, researchers exposed those cells to bisphenol A. They found that low doses of the chemical suppressed levels of adiponectin, a hormone produced in the fat cells that improves insulin sensitivity and reduces inflammation. Adiponectin also is known to protect people from metabolic syndrome, a condition that substantially increases the risk of developing heart disease.
That study, which was funded by the National Institutes of Health, was published in Environmental Health Perspectives.
Rep. John D. Dingell (D-Mich.), chairman of the Committee on Energy and Commerce, said the JAMA study adds to the growing concern about the chemical, especially its effects on infants and fetuses.
"To date, the Food and Drug Administration has ignored the totality of research available to it and instead focused myopically on industry-funded research," he said in a statement.
"One would hope that the FDA will take careful notice of this new research during its Science Board meeting on bisphenol A. The committee will be watching carefully to determine whether that meeting is a legitimate and open discussion based on all of the available science, or a continuation of FDA's pattern of refusing to take into account the totality of publicly available scientific research on bisphenol A."
The cumulative evidence from hundreds of animal and lab studies now is supported by a solid study in people, said Jerry Heindel, a science administrator with the National Institute of Environmental Health Sciences, part of the NIH.
"It's all coming together," he said. "How much data do you need before you say something has to be regulated?"
Although the study does not prove causation, "It tells us what happens in animals, happens in humans," said Ana Soto, an endocrinologist with Tufts University.
She said she was already swayed by the animal studies.
"The cumulative evidence is very strong," she said.
WHAT YOU CAN DO
There are some relatively simple things you can do to minimize your exposure to bisphenol A. Many scientists say you can start by focusing on things you eat or put in your mouth that come in contact with the chemical. Other suggestions include:
- Read labels. If a company goes to the trouble of making a plastic product that does not contain bisphenol A, the maker is likely to label it.
- Use plastics that have the recycling numbers 1, 2 or 5. Avoid those labeled with recycling numbers 3 (polycarbonate) or 7 (PVC).
- Don't heat foods or drinks in plastic, regardless of their recycling numbers. Use glass or ceramic.
- Use glass baby bottles or plastic baby bottles labeled "bisphenol A-free." Born Free is one company that makes plastic bottles without bisphenol A. Another option: plastic baby bottle liners made with polyethylene, such as the Playtex Nurser System.
- Before storing heated foods in plastic containers, wait until the food cools.
To read the Journal Sentinel's series on the chemical bisphenol A, go to www.jsonline.com/chemicalfallout.
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