So far, in this series of articles, I have focused on studies that have shown parabens in a poor light, in toxicological terms, and attempted to correct errors and misperceptions, and place the results in a realistic context. In this article, I am going to concentrate on sharing some studies that actually have good news for parabens lovers (ie, me and possibly 3 other people on the planet!). I am doing this to demonstrate that not all toxicity studies on the various parabens have come up with results that may worry people. I know that this sounds unlikely, but please bear with me – these studies tend not to get quite the same level of publicity as the negative ones!
One of the most frequently quoted “facts” about parabens is that they mimic oestrogen. This is not true, but it is understandable how there may be some confusion over this. As noted in Part 1 of this series, Routledge, et al determined that butylparaben showed oestrogenic activity measured at 100,000 times weaker than oestradiol (a natural oestrogen). This has been wrongly extrapolated and misinterpreted as being that butylparaben(and ALL parabens!) mimics oestrogen. Whilst the terminology may be confusing, oestrogenic activity and oestrogen mimickry are very different effects. This is NOT semantics! Oestrogenic activity is simply a measure of the relative power of a substance to bind to oestrogen receptors in the body. It is expressed as a comparative figure against the binding power of oestradiol. Once bound, anything can happen, depending upon the precise nature of the bound substance. It may just sit there and do absolutely nothing . . . . or it may mimic oestrogen . . . or it may partially mimic oestrogen – and all shades in between.
The following study was critical in this particular debate:
Comparison of the global gene expression profiles produced by methylparaben, n-butylparaben and 17β-oestradiol in MCF7 human breast cancer cells.
D. Pugazhendhi, A. J. Sadler, P. D. Darbre, J. Applied Toxicol. 27 (1), 67 – 77 (2006)
Put simply, it is the comparison of the effect on global gene expression that determines the extent to which a substance truly mimics oestrogen. The authors concluded:
“The majority of genes were not regulated in the same way by all three treatments . . . . . although parabens possess oestrogenic properties, their mimicry in terms of global gene expression is not perfect and differences in gene expression profiles could result in consequences to cells that are not identical to those following exposure to 17β-oestradiol.”
In other words, parabens are NOT oestrogen mimics, and anyone who says otherwise is either confused or deliberately giving out disinformation. It is ironic that one of the authors of this important study was the same Dr. Darbre who caused much of the furore over parabens in the first place! It is also strange that this study was not given the same level of publicity as the one that “detected” parabens in human breast cancer tissue.
It has also been claimed that parabens may have an effect on reproductive mechanisms. The following study addressed this issue:
Systemic uptake of . . . . butyl paraben following whole-body topical application and reproductive and thyroid hormone levels in humans
N. R. Janjua, G. K. Mortensen, A-M. Andersen, B. Kongshoj, N. E. Skakkebaek, H. C. Wolf, Environ. Sci & Technol. 41, (15), 5564 – 5570 (2007)
This study (which also looked at a couple of phthalates) used the application of a cream containing 2% butylparaben on human skin. It should be noted that a typical concentration of butylparaben is closer to 0.02%, so the study used a concentration approximately 100 times greater than would normally be experienced. The researchers then measured the concentrations of reproductive and thyroid hormones and concluded that “the systemic concentrations achieved . . . in this short term study did not seem to interfere with the hypothalamic – pituitary – gonadal and hypothalamic – pituitary – thyroid axes, as the endogenous levels of reproductive and thyroid hormones were unaffected. So, whilst this was only a very short term study, the huge overdose compensates at least in part for that slight shortcoming, and it would appear that butylparaben does not affect the reproductive and thyroid systems. Given that there is no evidence that butylparaben accumulates in the body (it is known to be excreted in urine in its intact, conjugated and metabolised forms), the findings of this study are likely to be robust.
There are other studies, along similar lines:
Effect of neonatal exposure to estrogenic compounds in development of the excurrent ducts if the rat testis through puberty to adulthood
J. S. Fisher, K. J. Turner, D. Brown, R. M. Sharpe, Environ. Health Perspectives, 107 (5), 397 (1999)
This study used an injection of 2mg/kg bodyweight per day for 17 consecutive days. (This dose is equivalent to a 60kg human using around 400g/day of product containing 0.03% butylparaben. Whilst this is not a massive overdose, it is substantial. To put this in context, a typical daily average use of cosmetics is estimated by COLIPA to be 17g, and by no means all the products used would contain butylparaben, so this is an overdose by a factor of at least 23 times.) The authors concluded that “administration of [butyl]parabens (2mg/kg/day) had no detectable effect on any parameter at day 18”. This means that butylparaben, under the conditions of the study, did not affect the reproductive system of the male rat.
One researcher (Oishi) has published several papers on the effects of parabens on sperm, but the SCCS reviewed these studies and requested more information as they felt that details were lacking. The SCCS got no response from Oishi and subsequently, her studies were not considered in the more recent SCCS Opinions on parabens. I will discount them for the same reasons!
So, in conclusion from the studies investigated in this article, it can be seen that parabens do NOT mimic oestrogen, and that there is reasonable evidence to suggest an absence of reproductive effects.