A first-of-its-kind study of a small group of people exposed to a very small amount of bisphenol-A (BPA) is raising questions about the federal government’s stance that low doses of the common chemical are safe — as well as the ethics of conducting such an experiment on humans. The controversial study suggests that BPA exposure deemed safe by the feds could alter the amount of insulin released and elevate people’s type 2 diabetes risk, Environmental Health News reports.
Featured image credit Simon Zhu.
2018 Study Abstract
Aims
Human cross-sectional and animal studies have shown an association of the chemical bisphenol A (BPA) with insulin resistance, type 2 diabetes and other metabolic diseases, but no human experimental study has investigated whether BPA alters insulin/C-peptide secretion.
Methods
Men and post-menopausal women (non-diabetic) were orally administered either the vehicle or a BPA dose of 50-µg/kg body weight, which has been predicted by U.S. regulators (FDA, EPA) to be the maximum safe daily oral BPA dose over the lifetime. Insulin response was assessed in two cross-over experiments using an oral glucose tolerance test (OGTT; experiment 1) and a hyperglycemic clamp (HG clamp; experiment 2). Main outcomes were the percent change of BPA session measures relative to those of the control session.
Results
Serum bioactive BPA after experimental exposure was at levels detected in human biomonitoring studies. In the OGTT, a strong positive correlation was found between HbA1c and the percent change in the insulinogenic index (Spearman=0.92), an indicator of early phase insulin response, and the equivalent C-peptide index (Pearson = 0.97). In the HG clamp study, focusing on the later phase insulin response to a stable level of glucose, several measures of insulin and C-peptide appeared suppressed during the BPA session relative to the control session; the change in insulin Cmax (maximum concentration) was negatively correlated with HbA1c and the Cmax of bioactive serum BPA.
Conclusions
This exploratory study suggests that BPA exposure to a dose considered safe by U.S. regulators may alter glucose-stimulated insulin response in humans.