Korean researchers have found another small piece of evidence that the chemical BPA might affect health — this time by temporarily raising people's blood pressure.
People who drank out of cans lined with resins containing BPA had a brief increase in their blood pressure, Dr. Yun-Chul Hong of Seoul National University College of Medicine in South Korea and colleagues found.
Environmental groups have been lobbying for years for the Food and Drug Administration to ban bisphenol A, also known as BPA. The FDA has said that BPA can leach out of the plastic that it's used to make, and most people have some BPA in their bodies. The dispute is over whether it's harmful. The FDA continues to say all the evidence shows it's safe.
But several studies have suggested a link between BPA and heart disease or obesity.
For the latest study, published in the American Heart Association journal Hypertension, Hong and colleagues studied 60 people, mostly elderly women. They drank soy milk out of either a can or a bottle, and the researchers measured how much BPA was in their urine and also measured heart rate and blood pressure.
Each volunteer came back three separate times and each drank out of a glass bottle, which contained no BPA, a can lined with a compound containing BPA or one of each. It was the same brand of soy milk and the drinks were stored at the same temperature whether in bottles or cans.
"The urinary BPA concentration increased after consuming canned beverages by more than 1,600 percent compared with that after consuming glass bottled beverages," Hong's team wrote in their report.
"Systolic blood pressure adjusted for daily variance increased by 4.5 mmHg after consuming two canned beverages compared with that after consuming two glass bottled beverages, and the difference was statistically significant." Systolic blood pressure is the "top" reading, and people should aim for a reading of 120 or below.
Blood pressure can vary naturally during the day, and a four-point difference is within that variable range, so it's not clear if there would be any health effects of the rise. Heart rate was not affected by BPA.
"While a 4.5 mmHg difference sounds small, and this study does not tell us how long that elevation might last, when you translate that difference to a large population it could have real meaning in terms of heart attacks, strokes and heart failure for people who drink such beverages frequently," said Dr. Donald Lloyd-Jones at Northwestern University in Chicago, who was not involved in the study.
"Maybe (it's) one more reason not to drink canned beverages — sugar-sweetened, diet or other."
And a small increase could be a problem for people who already have high blood pressure, Hong said. "A 20 mmHg increase in systolic blood pressure doubles the risk of cardiovascular disease," he said.
Other studies have suggested a possible link between BPA and heart disease. It's hard to tell, because people who eat a lot of canned food or drinks may have other habits or risk factors that affect their health.
For instance, in 2012 researchers reported in the Journal of the American Medical Association that kids with the highest levels of BPA in their urine were twice as likely to be obese as those with low levels of the chemical.
The new study may fuel the debate over BPA, which the food industry is gradually removing from cans anyway because of consumer demand. The FDA has barred the use of the chemical in baby bottles and children's sippy cups, but is not yet convinced that BPA must be completely banned.
The compound can help keep food fresh. It helps harden plastic and can help a lining do a better job of sealing out bacteria.
In 2008, the Natural Resources Defense Council asked the FDA to prohibit the use of BPA in human food packaging. The FDA refused.
"In the fall of 2014, FDA experts from across the agency, specializing in toxicology, analytical chemistry, endocrinology, epidemiology, and other fields, completed a four-year review of more than 300 scientific studies," the agency says in its latest update on BPA.
"The FDA review has not found any information in the evaluated studies to prompt a revision of FDA's safety assessment of BPA in food packaging at this time," it added. "Pharmacokinetic and biomonitoring data continue to support our understanding that BPA is quickly and efficiently metabolized once ingested." In other words, FDA says the body excrete the compound.
"FDA's current perspective, based on its most recent safety assessment, is that BPA is safe at the current levels occurring in foods."