Is It Bad For You? (pt. 2)
Have you ever picked up a water bottle and seen “BPA free” on the tag and said to yourself, “well that’s nice. But I don’t actually know what BPA is, so I’m not sure how excited I’m supposed to be.” That was me, until this article.
So for anyone not familiar with this chemical compound, Bisphenol A (BPA) is a material found in many plastics and cans. It’s also found in receipts, plastic wrap, paper and plastic cups, and even in dental sealant. It’s basically in everything except for baby products at this point. It leeches out when heated and is easily absorbed by the body.
Its shape is actually similar to estrogen and can therefore mess with the endocrine system by binding estrogen receptors. What is interesting is that in the animals tested, low doses of BPA have a different effect than higher doses. In a study published in 2018 by an Indian group from Annamalai University on the effects of different doses of BPA in female rats (10, 50, & 100μg/kg body weight per day), the lowest dose of BPA decreased levels of estrogen and progesterone in the rats but the higher doses did not. It also changed lipid metabolism more with lower doses than high doses(1).
For reference, the WHO estimates that the average human exposure levels to BPA are less than 0.6–1.5μg/kg body weight/day for adults and 0.3–1.1μg/kg bw/day for children and teenagers(2), so quite a bit lower than even the lowest dose tested in the study.
The US National Toxicology Program (a program supported by the US Department of Health and Human Services) did a huge 2 year study on BPA in rats by farming out the different body organs to different institutions. Well, not the actual organs, just the research on those organs. They specifically wanted to study the toxicity of BPA beyond the endocrinological effects of activating the estrogen receptors. They set up the study so that each group fed rats in doses of 2.5–25,000μg/kg body weight from either 6 days after gestation until 21 days or for two whole years. As a control, they fed other rats ethinyl estradiol (one of the ingredients in birth control pills) which also activates estrogen receptors.
In short, amongst all the organs studied, researchers found that BPA can cause structural changes in certain parts of the brain in fetuses exposed, and changes in gene expression in some parts of the brain with lifetime exposure.
Lower levels of BPA also resulted in an increase in cancer of mammary tissue, affect ovarian follicle numbers and sex steroid levels, and differences in the estrous cycle and uterine pathology of the rats(2). Oddly, the FDA concluded from this study that BPA is nothing to worry about but recommend not giving babies products with BPA in them.
Correlational studies in humans have linked higher BPA exposure (measured in urine samples) to reproductive problems, endometriosis, miscarriage, premature birth, obesity and diabetes, and coronary disease(3).
In 2015, the European Food Safety Authority (EFSA) lowered the tolerable daily intake (TDI) levels from 50μg/kg to 4μg/kg. In April of this year, they revised their previous recommended TDI to 0.2ng/kg (20,000 times less than 4μg/kg)(4). The FDA still has a TDI of 50μg/kg but after pressure from a variety of different organizations petitioning for stricter regulation of BPA, they have agreed to re-evaluate(5). Which I’m sure they will do any day now. Aaaaaaaany day now.
The good news is that there are now many BPA substitutes, like BPS and BPF that are being used in plastics and resins instead of BPA. The bad news is that they are potentially just as bad as BPA. They have similar structures and can activate estrogen receptors almost as well as BPA if not better(6).
BPA alternatives BPS, BPAF, and TMBPF were found to be toxic in human and rat stem cell cultures(7). BPS, diphenyl sulfone, BPF, and BPAF along with BPA were shown to adversely affect the production of germ cells in mice(8). BPS and BFA had pro-tumorigenic effects on human mammary tissue in culture(9).
Many products labeled “BPA free” contain one of these BPA substitutes, so even though we think they are healthier and safer, they probably aren’t. And since food containers don’t come with an ingredients list like their contents do, it’s impossible to know what contains these harmful chemicals. My advice? Don’t heat food in plastic containers or wash plastics in hot water or in the dishwasher and consume food and drinks from cans sparingly. And hope for the best I guess.
References:
1. Thilagavathi S, Pugalendhi P, Rajakumar T, Vasudevan K. Monotonic Dose Effect of Bisphenol-A, an Estrogenic Endocrine Disruptor, on Estrogen Synthesis in Female Sprague-Dawley Rats. Indian J Clin Biochem. 2018 Oct;33(4):387–396.
2. CLARITY-BPA Research Program. NTP Research Report on the Consortium Linking Academic and Regulatory Insights on Bisphenol A Toxicity (CLARITY-BPA): A Compendium of Published Findings: Research Report 18. Research Triangle Park (NC): National Toxicology Program; 2021.
3. Martínez-Ibarra A, Martínez-Razo LD, MacDonald-Ramos K, Morales-Pacheco M, Vázquez-Martínez ER, López-López M, et al. Multisystemic alterations in humans induced by bisphenol A and phthalates: Experimental, epidemiological and clinical studies reveal the need to change health policies. Environ Pollut. 2021 Feb 15;271:116380.
4. Bisphenol A | EFSA [Internet]. [cited 2023 Aug 26]. Available from: https://www.efsa.europa.eu/en/topics/topic/bisphenol
5. FDA agrees to reevaluate safe levels of BPA in food packaging [Internet]. [cited 2023 Aug 26]. Available from: https://www.healio.com/news/primary-care/20220603/fda-agrees-to-reevaluate-safe-levels-of-bpa-in-food-packaging
6. Moon MK. Concern about the Safety of Bisphenol A Substitutes. Diabetes Metab J. 2019;43(1):46–48.
7. Harnett KG, Chin A, Schuh SM. BPA and BPA alternatives BPS, BPAF, and TMBPF, induce cytotoxicity and apoptosis in rat and human stem cells. Ecotoxicol Environ Saf. 2021 Jun 15;216:112210.
8. Horan TS, Pulcastro H, Lawson C, Gerona R, Martin S, Gieske MC, et al. Replacement Bisphenols Adversely Affect Mouse Gametogenesis with Consequences for Subsequent Generations. Curr Biol. 2018 Sep 24;28(18):2948–2954.e3.
9. Winkler J, Liu P, Phong K, Hinrichs JH, Ataii N, Williams K, et al. Bisphenol A replacement chemicals, BPF and BPS, induce protumorigenic changes in human mammary gland organoid morphology and proteome. Proc Natl Acad Sci USA. 2022 Mar 15;119(11):e2115308119.
