This content originally appeared on Everyday Health. Republished with permission.

By Ross Wollen

Medically Reviewed by Anna L. Goldman, MD

Bisphenol A (BPA), a chemical that leaches into food from plastic packaging and metal cans, can significantly reduce insulin sensitivity according to experts. The chemical, which is pervasive in our food supply, may be a contributor to rising rates of type 2 diabetes.

What Is BPA?

BPA is an industrial chemical that is used extensively in the manufacturing of polycarbonate plastics, which are frequently used as food packaging, and the epoxy resins that line the interior of food cans. BPA is not intended to be eaten, but small amounts can contaminate food and beverages, especially when the packaging material is warmed up.[1]

Because BPA is found in such a vast number of food products, most of us are consuming measurable levels of the chemical. Over 90 percent of Americans have been found to have detectable amounts of BPA in their urine.[2]

How BPA Disrupts the Endocrine System

BPA is an endocrine-disrupting chemical (EDC). EDCs interfere with the proper functioning of hormones in a variety of ways, such as by mimicking hormones, blocking them, or altering their concentration in the body.[3]

BPA’s strongest endocrine-disrupting effect is its tendency to mimic estrogen. BPA, which is structurally similar to estrogen, competes with estrogen to bind to special receptors in fat cells, provoking both inflammation and cell growth. Some experts fear that this effect leads to an increased risk of cancer, among other long-term health issues.[4]

Insulin, another hormone, binds to the same fat cells. When BPA drives fat cell dysfunction, it also reduces the body’s ability to respond to insulin. In short, BPA causes insulin resistance and high blood sugar, a signature cause and feature of type 2 diabetes.

BPA and Insulin Sensitivity

Unpublished data presented at the 2024 American Diabetes Association’s Scientific Sessions conference has shown that BPA consumption triggers insulin resistance directly and rapidly. While many previous studies have found a correlation between BPA levels, insulin sensitivity, and type 2 diabetes, this was the first randomized controlled trial to study the chemical’s immediate effects in humans, says Todd Hagobian, PhD, a professor of kinesiology at California Polytechnic State University in San Luis Obispo.

The study, which had yet to be peer-reviewed at the time of the conference, evaluated BPA consumption in 40 healthy young adults. Every day, each of these volunteers ate a vanilla cookie. Half of the cookies were sprinkled with the maximum “safe” amount of BPA, as determined by the United States Environmental Protection Agency (EPA). The volunteers otherwise ate a balanced diet for seven days.

At the beginning and end of the weeklong session, all volunteers submitted to a glucose clamp test, a complex technique that is the gold standard for measuring insulin resistance. This test measures how much glucose is required to keep blood sugar levels steady at a healthy level. The participants who consumed BPA experienced “about a 9 percent decrease in peripheral insulin sensitivity,” says Dr. Hagobian.

The result may confirm what many researchers have long suspected. Many larger observational studies across the world have found significant correlations between BPA levels and markers of insulin resistance or type 2 diabetes:

Women with a higher concentration of BPA in their urine have higher fasting blood glucose and more insulin resistance.[5]
Adults with more BPA in their blood have more insulin resistance, more inflammation, and a higher biological age.[6]
Women with a higher exposure to BPA are more likely to report that they have type 2 diabetes.[7]

Peripheral insulin resistance, which refers especially to insulin signaling dysfunction in the skeletal muscle, is also associated with accelerated aging and Alzheimer’s disease.

Hagobian says that BPA exposure is unlikely to play as large a role as some of the major risk factors for type 2 diabetes, particularly obesity, genetics, lack of exercise, and poor nutrition, “but these main factors don’t explain all the cases of type 2 diabetes. We think that BPA could be one of those other factors.”

Should We Reduce Our BPA Exposure?

The U.S. Food and Drug Administration (FDA) has declared that BPA — at least in the low doses that people regularly encounter in the food supply — is safe.[8]
But it has been a decade since the FDA has publicly reviewed the science behind BPA contamination, and some experts are nervous about the omnipresent chemical’s impact on public health.

“With the increase in diabetes in the U.S., it is our duty to ensure safety within our products and in our homes,” said Robert Gabbay, MD, PhD, the chief scientific and medical officer of the American Diabetes Association (ADA), in a statement. Dr. Gabbay said that the study demonstrating BPA’s effect on insulin sensitivity “is only the beginning of highlighting the need for informed public health recommendations and policies.”

Hagobian says: “These results suggest that maybe the U.S. EPA safe dose should be reconsidered and that healthcare providers could suggest these changes to patients.”

In the past, the FDA has changed some regulations in response to worries about BPA. The use of BPA has been banned from food packaging intended for infants and young children, such as baby bottles, sippy cups, and infant formula. BPA’s risks are believed to be elevated among fetuses and infants.[9]

But even if BPA’s effect on the metabolism is only minimal, Hagobian advises making the effort to reduce our BPA exposure. “We probably should take this into account when we’re purchasing food.”

“It’s a small to medium effect, but that doesn’t mean we can’t make small changes. We can reduce our use of cans, try to get rid of plastics and use stainless steel or glass, and reduce that detrimental factor.”

He points to canned foods as the “greatest risk of exposure.”

In recent years, many manufacturers have switched to BPA alternatives, and the amount of BPA contamination in canned foods has dramatically declined.[10] Unfortunately, switching to a “BPA-free” canned beans or veggies doesn’t necessarily put you in the clear. “You can purchase canned food that is labeled as BPA-free, but the regulation is not great on this. It’s likely that they use an analogue that might also be bad. We don’t really know.”

Hagobian and his family have made these changes themselves: “We’ve gotten rid of all the plastics in our house and tried to minimize the amount of canned food.”

The Takeaway

BPA contaminates much of the food that we eat. This chemical interferes with our hormonal system, driving insulin resistance which could contribute to type 2 diabetes. Fortunately, simple changes to your food purchasing and storage habits will help reduce the risk.

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