By Sheila Steffen, CNN
(CNN) - Rachel Noerdlinger says she felt "a big void" when she was in her 20s and went through an identity crisis.
"My parents thought we could be color-blind, and they raised us in an environment where we didn't talk about race," said Noerdlinger, who is black.
Adopted by white parents and raised in New Mexico, she grew up without any knowledge of where she came from.
"It was hard. I went through a lot of different confusions."
She is quick to point out how grateful she is for her adoptive parents. And although she would not change her experience, she offers this advice: "At the end of the day, the most important thing to your child's well-being is that he or she is around diversity."
Thirty-nine percent of adopted children in America have parents of a different race or ethnic group. Domestically, transracial adoptions were made easier by the Multiethnic Placement Act in 1994, which essentially keeps race from being a factor in adoptions. Still, the majority of transracial adoptions are international; others are from foster care and from private adoptions.
"Families are way ahead of where they were 10 or 15 years ago," said Susan Caughman, editor and publisher of Adoptive Families. "Today, parents adopting children of different races other than their own realize they need to be in their culture of origin in order to develop a strong sense of identity and self. It's no longer families pretending they are adopting white children."
World-renowned chef Marcus Samuelsson had only to step out of his house in Sweden, where he and his sister grew up, to know that he was different. "People came up to us all the time. It was from touching my skin to touching my sister's hair."
He and his sister are Ethiopian, adopted by Swedish parents. He says that facing issues of race and identity head-on during his upbringing helped give him a strong sense of self. "We dealt with it. Mom always turned everything that was an obstacle into confidence."
Today, he feels at home in both Stockholm and in Harlem, New York, where he lives and has a restaurant. "Don't be naive about the questions that are going to come," he advised. "Race will definitely come up. Be informed about it."
For decades, the National Association of Black Social Workers had opposed transracial adoptions, believing that black children should not be placed in homes of those of a different cultural background. The stance, taken in 1972, came during the civil rights movement because a number of African-American families were being screened out of the adoption process, says the group's vice president, Toni Oliver.
"We believe race should have preference in adoption and that a black child should be placed with a black family wherever possible," Oliver said.
In recent years, the group has softened its position but says it remains dedicated to preserving black families.
Today, Noerdlinger has a strong identity, and her life has come full circle. She works as a publicist for the Rev. Al Sharpton and is very involved in civil rights.
"It's fate that I would be raised outside of the black community," she said, "but unite later in life with someone that is so deeply embedded in the black community."
Soledad O'Brien's documentary "Who is Black in America?" airs at 8 p.m. ET/PT on December 9 on CNN.