Bisphenol A, abbreviated to BPA, is a synthetic chemical agent that is used in plastic food and beverage containers such as baby bottles. It is also a component of the lining of canned metal food cans. BPA can leach out from the container and contaminate the food inside, particularly when exposed to high temperatures. Recently, BPA has been implicated in many adverse health conditions, including an increased risk for obesity.
According to recent research published in the Environmental Health Perspective, the estrogenic properties of BPA can disrupt pancreatic beta-cell function. The beta cells store and release insulin, the primary hormone involved in maintaining appropriate blood-sugar levels. Low-dose, long-term exposure to BPA caused a rise in insulin production that lead to insulin resistance. Other studies have indicated that elevated insulin levels are a risk factor for obesity.
Increase in Fat Cell Production
Obesity is an increase in either the number or size of fat cells, also called adipocytes. The estrogen-like effects of BPA has been shown in a Japanese study to cause both hyperplasia (an increase in the number of fat cells) and hypertrophy (an enlargement of the fat cells) in laboratory mice. The effect was even greater when an increase in insulin production was simultaneously occurring.
A more recent study led by Tufts University scientists confirmed the results. Exposure to BPA increased the fat cell production in laboratory test mice whose mothers had been exposed to the chemical, despite holding other factors constant, such as calorie intake and physical activity. Those mice produced offspring that became an average of 15% heavier in adulthood.
Thyroid and Endocrine Dysfunction
BPA is an endocrine disruptor, which is an outside chemical that can mimic a natural body hormone and fool the body into over-responding, such as increasing body mass through growth hormone or stimulating insulin production when it is not needed. A 2007 study found that BPA can bind to the thyroid hormone receptor, interrupting its function. Thyroid conditions, particularly hypothyroidism, have been implicated in weight gain.
The Debate from Plastics Manufacturers
Some groups, including the American Chemical Council, have refuted claims that BPA leads to adverse health conditions, including obesity. They state that the claims presented to date have been based upon a small number of studies that have limitations, including small sample population, limited dosing levels of the chemical, and lack of consistency in the results, and that 50 years of study on plastics containing bisphenol A have concluded that the chemical is safe.
The Most Recent FDA Stance
In January 2010, the FDA announced plans to review the available data and make a determination on the appropriate levels of BPA allowed in food and beverage containers, particularly those that are for use by infants and children. The current level that is considered safe for exposure to BPA is 50 micrograms per kilogram per day, according to data from the Environmental Protection Agency.