"Being sexualised as a child, I think, took away from my own sexuality because it made me afraid," Portman told Shepard.
"It made me feel like the way I could be safe was to be like, 'I'm conservative, and I'm, you know, serious, and you should respect me, and I'm smart and like, don't look at me that way'," she said.
"But at that age, you do have your own sexuality, and you do have your own desire, and you do want to explore things, and you do want to be open. But you don't feel safe, necessarily, when there's, like, older men that are interested, and you're like, 'No, no, no, no'," she explained.
So, in response, the actress build "fortresses" that "didn't allow the full expression of who I was at that time", she admitted.
"I would start choosing parts that were less sexy because it made me worried about the way I was perceived and how safe I felt," she said.
"So many people, I think, had this impression of me that I was, like, super serious, and like prude and conservative," she said. "I realise I consciously cultivated that because it was a way to make me feel safe. That, 'Oh, if someone respects you, they're not going to objectify you'."
Portman went on to say that this approach "hinders" the natural development, because "you're creating a self defence" to "be immune to any weirdness".
In the end, "it worked out, luckily", she said. "I mean, I was safe."
Shepard claimed that it's the "opposite" of the Disney stars who start in those innocent roles and end up going to the extreme and claiming their sexuality.
"It's totally true, and it's so weird because it's, like, I was auditioning for all that stuff, too, and I like never got it as a kid. I always got like the dark, kind of sexy, young girl," Portman laughed.
The actress told a story of a time she went for commercial products like cereal, "and they'd be like, 'No way'. I was just not cute and chipper."