People have small increases in blood pressure after drinking from cans lined with material that includes a common chemical, South Korean researchers say.
When can linings contained bisphenol A - more commonly known as BPA - systolic blood pressure (the top number) went up by about 5 millimetres of mercury (mm/Hg), researchers found.
"I would like to recommend consumers use fresh foods or glass bottled foods rather than canned foods," said Dr. Yun-Chul Hong, the study's senior researcher from the Seoul National University College of Medicine. "I also hope manufacturers develop and use healthy alternatives (instead) of BPA for inner lining of the can containers."
BPA, which is found in many plastic bottles and the lining of cans, has been used in food packaging since the 1960s, according to the U.S. Food and Drug Administration (FDA). The chemical may migrate from packaging into foods, says the agency.
The FDA considers the chemical to be safe at current levels, and continues to "support the safety of BPA for the currently approved uses in food containers and packaging."
Read: Beware of BPA in baby bottles
Measurable amounts of the chemical are thought to be found in the vast majority of Americans. Preliminary studies also tie BPA to a number of conditions, including heart disease.
The researchers write in the journal, Hypertension, that BPA may affect blood pressure through its impact on the body's processing of the hormone oestrogen.
BPA levels and systolic blood pressure
For the new study, Hong and his colleagues had 60 people over age 60 come to their medical centre three times, with a month between each visit. Each time, they drank soy milk from cans or glass bottles. Tests showed that the soy milk in the cans had much higher BPA levels than the soy milk in the bottles.
Based on urine samples taken two hours after each drinking session, the researchers found that BPA levels in urine were highest after participants drank soy milk from cans.
There was no difference between overall blood pressure readings after participants drank from cans or glass bottles. There was, however, a difference in systolic blood pressure, the reading that measures the pressure when the heart pumps blood out to the body.
Read: BPA shown to disrupt thyroid function
Systolic blood pressure was about 5 mm/Hg higher after participants drank soy milk from cans than when they drank soy milk from bottles.
While a 5 mm/Hg is small and may not mean much to the average person, Dr. George Thomas told Reuters Health that this magnitude of an increase could translate into more heart disease and deaths over a large number of people.
Thomas, a blood pressure and kidney specialist at the Cleveland Clinic in Ohio, said the average person shouldn't be worried about BPA in cans until more studies are done.
"I think what's needed is bigger studies - more follow up," said Thomas, who wasn't involved with the new study. "What's really key is if this has any long-term impact."
Among the limitations of the study is that it only looked at one moment in time, Thomas said. Also, he pointed out, it was conducted on a small group of people at one medical centre. Furthermore, BPA concentrations may differ between South Korea and other regions.
"I would say it's intriguing, but more needs to come out of it prior to people just getting scared from cans or plastic bottles," he said. "I don't think it should be blown up to the point where people get scared from something we don't really know."
He does advise people stick to fresh fruit and vegetables, however, because canned foods tend to be high in sodium, which may increase blood pressure.
In a statement to Reuters Health, the American Chemistry Council (ACC) said the study inappropriately concerns and confuses consumers.
Read: BPA raises risk for childhood asthma
"This study's claim that BPA, which is safely used in can linings to protect food and beverages from contamination, 'may pose a substantial health risk' is a gross overstatement of the findings, an incredible disservice to public health, and runs contrary to years of research by government scientists," says the ACC, which is a trade organization based in Washington, D.C.
Hong said in an email that other studies found BPA exposure from canned foods and several papers found harmful effects linked to the chemicals.
"So, I think it is not too early to say that this level of BPA is harmful," he said.
Hong did say more studies are needed to see if the chemical influence blood pressure over a longer period of time.
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Image: Crumpled aluminium can on white background from Shutterstock