Gabrielle Union Teams with Knix to Bring Awareness to Menstruation, Menopause and Everything in Between (Exclusive)

If you're one of the 21.6 million people who follow Gabrielle Union on Instagram, you know she's the rare celeb who isn't afraid to reveal her real self.

Whether it's embracing her natural texture and grays in a hair tutorial or putting on a family fashion show in her living room with husband Dwyane Wade and 5-year-old daughter Kaavia James, the actor, entrepreneur and advocate has built her platform on honesty and humility, with a side of style inspiration (we're still talking about her Oscars look).

Now, Union, 51, is lending her candor and wisdom as the new global brand ambassador for intimate and apparel company Knix, which just launched its newest innovation with a range of leakproof, ultra-thin, no-show underwear.

To hear Union tell it, teaming with the brand for its latest “Knix for Life" campaign really resonated with her own desire to break down the stigmas and taboos surrounding women's health.

"The great thing about Knix and the great thing about where I'm at in life is that I want open communication, love, acceptance, resources and answers at every stage of my life, not just when I'm young and shiny," Union tells PEOPLE in an intimate sit-down about the partnership. "We need brands that are going to grow with us as we change and our bodies change and as life changes. And Knix is one of those companies, they are uniquely qualified to stay with us for the long haul."

Union, who first collaborated with Knix on its Life After Birth book in 2021, strips down to the brand's new leakproof ultrathin bikini underwear for the campaign, telling PEOPLE that products that pack extra protection are important at all stages.

"I like that Knix is with you from 13 to menopause and beyond," she shares. "You might discover that you have endometriosis or fibroids or cysts and those crazy periods that feel like hemorrhages, Knix is with you then. You have a baby. Nobody talks about the postpartum fun that is leaving your body for a minute. You need them then too. And when you go into perimenopause and your periods are 30 days — all the different reasons why people at different points in their lives will need a company to grow with them, not judge them and not focus their marketing dollars somewhere else, because our needs never really ends."

For Union, the partnership holds even deeper meaning as she grew up in an environment where her family did not talk openly about periods or the changes women go through.

"My parents just thought, 'She's smart so she must know. We don't really need to have a full on discussion,'" Union tells PEOPLE. "I was depending on other 11, 12, and 13 year olds — that's kind of how I fumbled my way through. I'm 51, but I remember all the times that I leaked in middle school and how mortifying that is. I think every person who's had a period has those moments that you remember vividly where you were, who saw it, was there a jean jacket or a sweatshirt to wrap around your waist. The humiliation of the proof that you have a period."

Union says her knowledge of the female reproductive system was so limited, she thought "babies came from your urethra."

"I remember the first time I was at a swim club and I got my period and I'm like, 'well, I can't swim.' And my peers said, 'use a tampon,' and I was like, 'I'm a virgin!,'" she recalls. "Just misinformation on top of misinformation. That was the day I discovered it was the other hole. You just don't know until you know."

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In her household, transparency is key. She's already having these conversations openly, and wants her family to feel comfortable talking about their health and needs.

"My mom is going to be 77 and she tells stories [I've never heard]. I don't want to learn about you at 77, I could have had a whole different relationship with you had I gotten these stories and this information and your fears, your hopes, your dreams when I was growing up," Union says. "I want Kaavia [5] and Zaya [16] to know me, not the illusion of what I want them to think."

Union adds that it took her decades to reach the kind of inner confidence that she's trying to instill in her girls.

"It was around my early to mid 40s where I stopped caring about pleasing everyone, being a master to everyone but myself," she says. "It gets you nowhere but feeling resentful and angry and frazzled, and I let it go. I just got more in tune to my needs, my wants, my desires, my thoughts and they were seen and understood and it attracted what it was that I truly wanted."