Reviews of Anti-Microbials and Diabetes/Obesity
A meta-analysis found that there was no significant association between maternal triclosan levels and neonatal birth weight, nor between children's urinary triclosan levels and their BMI (Liu et al. 2021).
Type 2 Diabetes and Obesity
Longitudinal Studies in Humans
A long-term study from Spain found that people with higher propyl paraben levels had an increased risk of type 2 diabetes after 23 years of follow-up (Salamanca-Fernández et al. 2020). A prospective study from the Netherlands found that people with higher paraben levels lost less weight on a diet than those with lower levels, and had a higher BMI (van der Meer et al. 2020). Mexican mid-life women with higher paraben levels had higher triglycerides and higher blood pressure 9 years later (Zamora et al. 2021).
Exposure During Development
Prenatal exposure to parabens may affect the growth of the fetus and child (Wu et al. 2018). A study that combines both human and animal evidence finds that in humans, maternal use of butyl paraben-containing cosmetics was associated with overweight in offspring in the first eight years of life, especially in girls (Leppert et al. 2020). In the U.S., prenatal propylparaben levels were consistently associated with an increased BMI and overweight/obesity in childhood (Berger et al. 2021).
In Denmark, prenatal exposure to butylparaben above the level of detection was associated with higher total body fat percentage in 7 year old boys. There were no associations between in utero exposure to methyl-, ethyl- or propyl parabens and body weight/composition, and no associations in girls (Damsgaard Højsager et al. 2021).
In Belgium, higher levels of ethyl paraben in the placenta were associated with lower cord blood glucose levels and lower BMI in early childhood, but also with higher cord blood GGT activity (a marker linked to metabolic syndrome) (Reimann et al. 2021).
Prenatal exposure to the antibacterial agent triclosan was not associated with weight or height in newborn boys, although slightly associated with smaller head circumference. Other phenols were associated with higher birth weight, and methylparaben continued to be associated with weight at age 3 (Philippat et al. 2014). However another study found that prenatal exposure to triclosan was associated with lower birth weight (Messerlian et al. 2018). Prenatal triclosan was not associated with fat mass during childhood either (age 4-9) (Buckley et al. 2016). Prenatal and early childhood exposure to triclosan was weakly associated with lower measures of adiposity at age 8 in girls, and not consistently associated in boys or overall (Kalloo et al. 2018).
Cross-sectional Studies in Humans
In U.S. adults, cross-sectional studies have found that levels of various parabens were associated with a lower risk of diabetes (Ward et al. 2020), and lower triglyceride levels (Pazos et al. 2020). In Canadian men, a cross-sectional study found that higher propyl paraben levels were associated with an increased risk of metabolic syndrome, while ethyl paraben levels were associated with a lower risk in women. Also in women, methyl paraben levels were associated with a lower risk of obesity, and methyl, propyl and ethyl parabens were associated with higher HDL cholesterol levels (Kim and Chevrier, 2019). Another cross-sectional study found that parabens are associated with an increased risk of obesity in Czeck women (Kolatorova et al. 2018). In Korean adults, those with higher paraben levels had a higher risk of diabetes and obesity (Lee et al. 2020). In Spanish adolescents, overweight/obese girls were more likely to have a higher dietary intake of parabens (Monteagudo et al. 2021).
In U.S. adults and children, triclosan was associated with lower measures of obesity (Li et al. 2015), as were parabens (Quirós-Alcalá et al. 2018). Among U.S. women, there was an increase risk of type 2 diabetes in those with higher triclocarban (but not triclosan) exposure levels, but no associations found among men (Xie et al. 2020). In U.S. adults, there was actually a lower overall risk of diabetes with higher levels of triclosan (Ward et al. 2020) but an increased risk of obesity with higher levels of triclocarban (Uche and King, 2020).
So there conflicting evidence so far.
Cross-Sectional Studies in Children
Triclosan was not associated with any body weight measurements in U.S. adolescents (Buser et al. 2014).
Triclosan was not associated with obesity in children from India (Xue et al. 2015). In children from China, however, exposure to triclosan and triclocarban was associated with increased risk of childhood obesity (Han et al. 2021).
Laboratory Studies: Type 2 Diabetes
Triclosan and benzo[a]pyrene lead to metabolic disorders in the liver including insulin resistance (as well as immune system changes) in amphibians (Regnault et al. 2016). In fact, low levels of both these chemicals cause prediabetes, glucose intolerance, and metabolic syndrome in frogs exposed over a lifetime, and may play a role in amphibian declines (Regnault et al. 2018). In mice, triclosan can also cause liver problems, specifically by affecting fat storage in the liver, and causing oxidative stress and inflammation (Huang et al. 2019). Triclosan causes non-alcoholic fatty liver disease (NAFLD) in zebrafish (Sun et al. 2020; Sun et al. 2021).
Laboratory Studies: Exposure During Development
In mice, maternal butyl paraben exposure induces a higher food intake and weight gain in female offspring (Leppert et al. 2020). Exposure to methyl paraben during development affected the gut microbiota of rats in adolescence, although the changes diminished as the rats aged into adulthood (even when the exposure continued) (Hu et al. 2016).
Exposure to triclosan during development affected the gut microbiota of rats in adolescence, although the changes diminished as the rats aged into adulthood (even when the exposure continued) (Hu et al. 2016). In zebrafish, probiotics actually can alleviate the intestinal metabolic problems resulting from exposure to triclosan, through modifying gut flora (Zang et al. 2019). In human gut cells, microbial community diversity and population size is significantly impacted by triclosan at a high doses, and after a 2 week recovery period, the community recovers (Mahalak et al. 2020).
Maternal exposure to triclosan led to metabolic effects in rat offspring in adulthood, resembling metabolic syndrome (Rabaglino et al. 2016). Maternal exposure to another similar anti-microbial chemical, triclocarban, also leads to metabolic changes in mouse offspring, including heavier body weight and changes in the liver and fat tissue (Enright et al. 2017). Triclocarban also affects the gut microbiota of lab animals (Yang et al. 2020). Early life exposure to triclosan and benzo[a]pyrene at levels found in the environment led to effects similar to pre-diabetes type and metabolic syndrome in frogs (Usal et al. 2019). In rats, exposure to triclosan during early life caused increased blood glucose, leptin, HDL/LDL cholesterol, and triglyceride levels, and in the liver caused lower glycogen levels and higher triglyceride levels. It also led to reduced diversity and altered composition of gut microbiota. These effects lasted a lifetime even without further exposure and accumulated over time (Ma et al. 2020). Exposure during development to a mixture of triclosan, phthalates, and perfluorinated compounds (based on the levels of these compounds found in pregnant Swedish women) affected metabolic rate, increased the number of fat cells and fatty tissue young zebrafish fed a calorie-rich diet (Mentor et al. 2019).
Life-long exposure to a mixture of triclosan and benzo[a]pyrene, at concentrations often found in natural ponds, induced metabolic syndrome in the offspring of frogs for multiple generations (Usal et al. 2021).
In cell studies, low doses of methyl- and propyl- parabens increased fat cell development of white fat cells and increased glucose uptake in white fat cells, but did neither in brown fat cells (Elmore et al. 2020).
In pre-fat cells, various parabens increase fat cell differentiation (Choi et al. 2021).
The Florence Statement on Triclosan and Triclocarban
"The Florence Statement on Triclosan and Triclocarban documents a consensus of more than 200 scientists and medical professionals on the hazards of and lack of demonstrated benefit from common uses of triclosan and triclocarban... Based on extensive peer-reviewed research, this statement concludes that triclosan and triclocarban are environmentally persistent endocrine disruptors that bioaccumulate in and are toxic to aquatic and other organisms.
... Because antimicrobials can have unintended adverse health and environmental impacts, they should only be used when they provide an evidence-based health benefit. Greater transparency is needed in product formulations, and before an antimicrobial is incorporated into a product, the long-term health and ecological impacts should be evaluated."
From Halden et al. (2017)
Type 1 Diabetes
Cross-sectional data from a large U.S. study (NHANES) found that of all chemicals measured, the association between autoimmune antibodies (not type 1 specific) and triclosan was statistically significant (Dinse et al. 2016).
In mice with type 1 diabetes, exposure to triclosan, in combination with a high-fat diet, causes nutritional imbalance and changes in gut microbiota, resulting in fatty liver disease (Yueh et al. 2020).
Exposure during pregnancy may be important for the woman (as well as the fetus), and contribute to gestational diabetes (Varshavsky et al. 2019). For example, higher paraben levels were associated with higher glucose levels in pregnant women (Bellavia et al. 2018), with gestational diabetes in overweight/obese pregnant women (Li et al. 2018), with higher weight gain during pregnancy (Wen et al. 2020), with lower blood pressure in pregnant women (Warembourg et al. 2018), and with various markers of metabolism in pregnant women (Zhao et al. 2020). But it also depends on the type of paraben; in Chinese women, ethyl paraben levels were positively associated with gestational diabetes, but not methyl paraben or propyl paraben (Liu et al. 2019). In general, the use of personal care products (which often contain parabens or other chemicals) is also linked to higher blood glucose levels in pregnancy (Bellavia et al. 2019).
Triclosan was not associated with gestational diabetes, impaired glucose tolerance, gestational weight gain, or metabolic effects on the fetus (Shapiro et al. 2018).
A study from China found a positive, but statistically non-significant association between women's triclosan levels and gestational diabetes (Ouyang et al. 2018). However a study from the UK found that triclosan levels were associated with a reduced risk of gestational diabetes (Fisher et al. 2018). Another Chinese study found that triclosan levels were associated with different blood pressure levels in pregnant women, with the changes depending on the sex of the fetus (Liu et al. 2019).
In animal studies, exposure to triclosan during pregnancy causes insulin resistance in mice (Hua et al. 2017).
Diabetes Complications and Control
A randomized controlled trial in Australia assigned people to use either triclosan or a placebo toothpaste for 5 years. Triclosan toothpaste led to a greater decrease in total and HDL cholesterol than placebo toothpaste. For kidney function, people with diabetes in the placebo group were significantly more likely to deteriorate than either patients with diabetes in the triclosan group or patients without diabetes in each group. These data suggest that triclosan toothpaste may influence some inflammatory biomarkers of cardiovascular disease, but not necessarily kidney or liver function (Cullinan et al. 2015).