September 12, 2017

expert reaction to study investigating exposure to phthalates and epigenetic changes in sperm

A study published in Human Reproduction suggested that exposure to phthalates – compounds found in plastics and personal care products – was associated with epigenetic changes to sperm DNA.

Dr Rod Mitchell, Paediatric Endocrinologist and Research Group Leader, MRC Centre for Reproductive Health, University of Edinburgh, said:

“This exploratory study involving a small number of men demonstrates associations between the levels of certain environmental chemicals in men and specific aspects of sperm biology. Whilst the study is well conducted and provides interesting findings, it must be borne in mind that association does not equal causation and it cannot be concluded that these specific chemicals are the cause of such effects on sperm. Further studies are required to replicate these findings in a larger population of healthy men and also to determine how such changes in sperm might impact on the health of the resulting embryo and subsequent generations.”

Prof. Allan Pacey, Professor of Andrology, University of Sheffield, said:

“There has been growing interest in whether epigenetic markers (a type of molecular post-it note) on sperm DNA can be influenced by environmental factors and have a role in male fertility. This is one of the first studies in humans to investigate this systematically by looking at these markers in the sperm of men undergoing IVF and correlating it to the concentration of phthalates found in their urine.

“Whilst a moderate association has been found between the concentration of some phthalates found in these men’s urine, and the number and position of these epigenetic markers along their sperm DNA, we should be cautious about how we interpret this data. For example, this is a very small study of only 48 men. Moreover, the results only describe an association and not “cause and effect”.

“Therefore, men currently undergoing IVF with their partners should not panic as it is very difficult to make any firm conclusions from this data. However, they should concentrate on being as healthy as possible by not smoking cigarettes (a much bigger epigenetic hazard in my view) and eating a sensible diet, with five portions of fruit and vegetables per day (paternal diet has been implicated as important in sperm DNA methylation).

“Men and women concerned about their fertility should go and see their family doctor if they have not been successful in achieving pregnancy after 12 months of intercourse without the use of contraception.”

Dr Jackson Kirkman-Brown, Reader in Human Reproductive Biology, University of Birmingham, & Science Lead, Birmingham Women’s Fertility Centre, said:

“This study presents initial data from a very small study, so caution is needed about the conclusions until the authors have completed a much larger dataset. It is important to stress that couples trying or who have conceived should not be concerned by this data.

“Nevertheless, the study once again emphasises a general data trend that it is not just making sperm that counts, the package of DNA that a sperm delivers to the egg, which is 50% of every human’s genetic material needs to be healthy. These is still a lot more knowledge needed but many studies point to the fact that a healthy male lifestyle including plenty organic fruit and vegetables may well be the best way to optimise a sperm’s DNA. In real life this is likely to mean avoiding junk or convenience food and gym supplements and instead just eating a healthy diet.”

* ‘Preconception urinary phthalate concentrations and sperm DNA methylation profiles among men undergoing IVF treatment: a cross-sectional study’ by Wu et al. published in Human Reproduction on Tuesday 12 September.

Declared interests

Dr Rod Mitchell: No conflicts of interest.

Prof. Allan Pacey: “Chairman of the advisory committee of the UK National External Quality Assurance Schemes in Andrology, Editor in Chief of Human Fertility and Trustee of the Progress Educational Trust (all unpaid). Also, recent work for the World Health Organisation, British Broadcasting Corporation, Purple Orchid Pharma (paid consultancy with all monies going to University of Sheffield). Co-applicant on a research grant from the Medical Research Council (ref: MR/M010473/1).”

Dr Jackson Kirkman-Brown: No conflicts of interest.