Last week, BuzzFeed News revealed that period trackers Mia Fem and Maya, which help their millions of users log everything from their bleeding to their mood to their sex habits, had been handing Facebook some of that information. The news seems like a good reason for everyone to go back to (or stick with) some kind of pen-and-paper situation for tracking menstrual cycles. But there are numerous upsides to using an app: Periods don’t adhere perfectly to a neat monthly schedule, which makes eyeballing when the next one will come difficult, and no one remembers to haul their old-fashioned physical calendar to the doctor’s office. Another underrated reason to stick with a digital tracker? Some apps share data not with Facebook but with scientific researchers. For them—and perhaps, in turn, you—the data sharing promises a deeper understanding of how menstrual cycles can vary, what side effects to expect from birth control, and better diagnostic tools for menstruation-related disease.

Computational biologist Laura Symul refers to datasets from menstrual apps as “a new microscope” into menstrual cycles. They help users track everything from mood to cramps to sex drive to even how your hair is behaving. In July, Symul published an assessment of the kinds of data that can be gleaned from tracking apps, offering a framework for digital epidemiologists to use it in their work. She looked at data from more than 200,000 users of two apps, Kindara and Sympto, totaling 2.7 million logs of cycles. Typically, studies on menstrual cycles have more like 50 participants, in part because it’s simply hard to encourage people to participate, says research psychologist Ruben Arslan. Last year, he published a study involving 1,000 women, which Slate’s Daniel Engber described at the time as a “massive survey study,” able to crush old claims from smaller, sloppier studies of the past. (For example: Women do not tend to put on sexy clothes when they’re ovulating, as had been suggested in published literature.)

Arslan is now working on new research using a massive, massive amount of data from the period tracker Clue, as an article on the app’s blog explains. In particular, he hopes to better understand the side effects of hormonal birth control, which many women are currently left to explore in their own personal and sometimes terrible game of trial and error. “Every side effect leaflet of the pill says it can change your libido, but there’s only been two larger randomized control trials that compare the pill to a placebo,” he says. “Any side effects that the pill may or may not have—it’s important to characterize them more thoroughly.” Down the line, his work could help people choose contraception that better suits them.

Another area where Clue data could offer valuable breakthroughs is in understanding and managing pain, another aspect of women’s health that is too frequently overlooked. This week, Symul finished up a draft of a paper on breast tenderness. That symptom can vary with age and birth control method and, when it shows up unexpectedly, can cause people to worry (usually unnecessary) that they might have cancer. Researcher Noémie Elhadad, a bio informaticist who has worked on models to better predict periods (on a paper she co-authored with Clue researchers, since it will, presumably, also benefit the app) is excited about the data’s promise in understanding signs of endometriosis—a disease for which it takes many people years to get a diagnosis.

Of course, all this comes at a privacy cost. One of the reasons the apps’ data is so useful is that an app is “a safe space where women can report the symptoms in an honest way,” says Symul. She recognizes the irony here: That sense of privacy is exactly what makes peeping in so valuable, whether the person looking is from a corporate conglomerate or is a well-meaning scientist. “It’s not my favorite aspect of my research,” says Symul. Elhadad says that she’s personally concerned about how intimate biometric data could be misused as reproductive rights are continually under threat. It’s not all that hard to imagine a world in which insurance companies deny features or access to people who are, say, using certain kinds of contraception. She said that while she wasn’t surprised to hear that apps were forking over data to Facebook, it still concerned her. “As a woman, I’m worried politically, more than anything else, because of all the ways that Facebook has been misused,” says Elhadad. “Maybe it’s a little dystopian of me to be paranoid.”

At the same time, Elhadad and the other researchers I spoke to hoped that users would look carefully at the various ways in which apps share their data, perhaps most specifically considering with whom they share it. Clue notes right in its App Store description that it doesn’t sell data, which seems true: Researchers go through a selection process and then get the data for free. Researchers have to follow rules for using that data, submitting studies to an institutional review board here they work for approval (not a flawless layer of oversight but significantly more than a private company purchasing data would be required to have). All data they use is anonymized, names removed and dates shifted: “I’m a Clue user, and I’ve never been able to find myself,” says Symul.

I’m a Clue user, too. And I was happy to learn how my data was being used, particularly because it was so easily accessible. I found the scientists I spoke to in this piece via Clue’s own blog, which includes an article titled “The Journey of a Single Data Point.” I was also glad to learn that if I did want to opt out of data collection, I could download the app and track my own cycle without making an account, an option that I previously hadn’t been aware of.

Still, I was also surprised to be confronted with published papers and to be discussing studies that I would essentially be a participant in. Elhadad acknowledged that right now the burden is on users to read through privacy policies to figure out where their data is going. Even as a science reporter, I just don’t have the motivation or bandwidth to consider how literally every app on my phone might be skimming me for my biometrics. Which is why I think, perhaps particularly after the creepy revelations about its competitors, and even longer-held skepticism that menstrual apps are of more use to advertisers and researchers than to women, Clue can go even further out of its way to alert users that it’s collecting data. Medical science isn’t a monolith of good stuff, either; as a consumer, I want to be kept in the loop on which studies my data might be contributing to, in case it turns out to, say, be headed to someone with a string of retracted papers and a retro idea of gender. I’d love if the app offered a message on where data is heading when someone opens the app for the first time, and a push alert when new papers are published or even when data is handed to a new lab. Beyond being the right thing to do, for users like me who care about advancements in women’s health, reminders that we’re contributing to research would be an extra incentive to painstakingly share.