New study questions whether sunscreen interferes with normal sperm function

A laboratory study on sperm cells, which tested 29 of 31 UV filters allowed in sunscreens in the United States or European Union, found 13 of those filters induced calcium ion influxes in the sperm cells at physiologically relevant doses. This, according to the researchers, interferes with normal sperm cell function.

Researchers in Denmark, a country that has a national campaign called “Do it for Denmark,” encouraging Danes to have more children to bring up worrisome birth rates, reported their findings April 1 at the Endocrine Society’s 98th annual meeting in Boston. The data is not yet published.

RELATED: Setting the record straight on sunscreen safety and efficacy

Obtaining the human sperm cells from fresh semen samples by healthy donors, the researchers tested the cells for calcium signaling in a buffer solution that, according to a press release on the study, resembled the conditions in female fallopian tubes.

Calcium ions’ movement within sperm cells, through calcium ion channels, plays a major role in sperm cell function, according to the study’s senior investigator Niels Skakkebaek, M.D., D.M.Sc., a professor at the University of Copenhagen and researcher at the Copenhagen University Hospital, Rigshospitalet. CatSper is a sperm-specific calcium ion channel that is essential for male fertility and is the main sperm receptor for progesterone. When progesterone binds to CatSper, it results in a temporary influx of calcium ions into the sperm cell, controlling several sperm functions necessary for fertilization, according to Dr. Skakkebaek.

Nine of the UV filters activated the CatSper channel directly, mimicking progesterone’s effect. And some of the UV filters were found to interfere with vital sperm functions in vitro, suggesting the need for clinical studies to investigate if UV filters indeed effect human fertility, according to the study’s abstract.

Of note to American dermatologists, 8 of the 13 UV filters that disrupted sperm cell function are approved for use in the United States, and are commonly found in not only sunscreens but also makeup, moisturizers and lip balms. They are avobenzone, homosalate, meradimate, octisalate (also known as octyl salicylate), octinoxate (or octyl methoxycinnamate), octocrylene, oxybenzone (also called benzophenone-3 or BP-3) and padimate O, according to the release.

Darrell S. Rigel, M.D., clinical professor of dermatology, New York University Medical Center, tells Dermatology Times that the findings of this study need to be verified before dermatologists become concerned.

“First of all, this [study] was done in a test tube environment; not in a live environment,” he says. “Number 2, we know all the benefits of sunscreen. We know sunscreen lowers the risk of skin cancer. So, we’re looking at something that has a noted benefit against a possible problem that really needs to be confirmed.”

When counseling patients, dermatologists should educate them about what science has confirmed, Dr. Rigel says.

“The most important thing to remember is we do this experiment with tens of millions of people every summer [as they wear sunscreen on our beaches and outdoors], and we’re not seeing effects that would be predicted by a study like this,” Dr. Rigel says.

The study’s authors in no way intend to change the recommendations on sunscreen use based on this data, according to study coauthor Anders Rehfeld, M.D., and Ph.D., student, department of growth and reproduction at Rigshospitalet - Copenhagen University Hospital and a member of the faculty in the department of cellular and molecular medicine at University of Copenhagen.

“Our experiments have been carried out in vitro only, and in vivo effects are still unknown. If, someway, a patient expressed concern about the use of chemical UV filters, my own personal advice would be to try and substitute the sunscreen with one with the same SPF but containing only physical UV filters, e.g. TiO2 or ZnO2,” Dr. Rehfeld tells Dermatology Times.

Disclosures:

Drs. Skakkebaek and Rehfeld report no relevant disclosures.

Dr. Rigel is involved in sunscreen efficacy research for Johnson & Johnson.