When filming the first series of The Bridge, we were doing an office scene where my character was in a meeting with colleagues, and I improvised by blurting out: “I’m on my period.” This was nothing unusual for Saga Norén, who’s known for her directness and deviation from social norms, but it’s not something we feel is acceptable in normal everyday life. That needs to change.

Periods are a natural process experienced by half the world’s population; they are a sign of life. So, why is the subject cloaked in secrecy and shame? I’m sure all women have faced the embarrassment of awkward period dramas, like being caught without a pad or tampon in a time of need. In these circumstances, should we feel embarrassed to ask a stranger to help us out?

And on a broader scale, the fact that people don’t talk about their periods is having a huge impact on women and girls around the world. One in three women have no access to a decent toilet, which is especially challenging during their period. If there isn’t one in schools, girls are more likely to miss classes or drop out altogether once they start their periods. According to recent research by WaterAid and Unicef, one in three girls in Sri Lanka, Bangladesh and Pakistan miss school days every month during their periods. Through my work with WaterAid, I’ve visited a school in Cambodia that had no decent facilities, forcing the children to find a private spot outside or go back home when nature calls. Imagine the impact that is having on their education, not to mention their health and confidence.

The stigma around periods and the lack of proper information means many girls rely on what their family or friends tell them, which is often inaccurate and can perpetuate menstrual myths. Even in Sweden, some believe you shouldn’t go into the woods while on your period as you’ll attract bears. This, I’m pleased to say, is not backed up by science.

In some parts of the world, the myths are even more restrictive on the lives of women and girls. Many are forbidden from partaking in everyday activities during their period, such as drinking milk, eating fruit and touching flowers. In more extreme cases, menstruating women can be banished from the home because of the belief they will bring bad luck. It makes me sad and angry to think of them being excluded in this way, and prevented from living life to the full – all because this most basic of bodily functions is so widely misunderstood.

Sanitary products are often unaffordable or simply not available for many, so many rely on homemade alternatives that are not always hygienic or absorbent. Period poverty is an issue we’ve seen in developed countries as well, and in the UK it is one that is starting to be taken seriously, thanks to the hard work of some amazing campaigners who are unashamedly making a noise about it. But we need this kind of action on a global scale. WaterAid is calling on women and men everywhere to talk about periods today on Menstrual Hygiene Day as part of its Period Proud campaign, to address the lack of accurate information and remove the stigma and taboos.

While we continue to keep silent on the subject of periods, women and girls will not be able to get the facilities and support they need to be able to deal with what is a normal part of life, hygienically and with dignity. We all need to play our part in opening up the conversation.

For me, my mother (who was a nurse) was always very open about periods, and she gave me the confidence to look forward to it. When it finally arrived, I went to tell her and she excitedly shouted out to anyone who could hear: “She’s got her period!” I want to do the same for my daughter, and my wish is that she will feel as proud and excited as I was. We will celebrate it together, just her and me; it’s an important moment. I want to be much more open about periods with men and women alike, and I hope others will join me.

• Sofia Helin is an actor in The Bridge and ambassador for WaterAid