Natalie Portman, the Israeli-American actress and outspoken vegan, appears in a new campaign for the People for the Ethical Treatment of Animals - speaking about famed Yiddish writer Isaac Bashevis Singer."Nowadays, many of us speak up for animals," the actress says in the video, released on Monday. "But it wasn't always like this. Decades ago, one man articulated the plight of animals so boldly, that the modern world couldn't ignore him. His name was Isaac Bashevis Singer."Singer, who died in 1991 in Florida, won a Nobel Prize in Literature in 1978 for his work. The writer, who was raised as an Orthodox Jew, was a prominent vegetarian for the last 35 years of his life. Several of his works referenced his compassion for animal suffering, and he even once compared it to the Holocaust, writing: "In relation to [animals], all people are Nazis; for the animals it is an eternal Treblinka."In the video campaign, Portman speaks of Singer's Jewish background and how it came to influence his decisions.The writer "grew up in the same part of Poland as my family, and like them, he fled the horrors of the Holocaust, but the cruelties he witnessed made Singer one of the most powerful writers of the 20th century," Portman says. "When Singer stopped eating animals, he famously declared: 'I did not become a vegetarian for my health, I did it for the health of the chickens." Last month, Portman released a film called Eating Animals, that she executive produced and narrated, based on the book of the same name by Jonathan Safran Foer. The documentary highlights abuses against animals raised for consumption, the perils of factory farming and the lost art of small, family-run productions. Portman has partnered up with PETA several times in the past, and isn't the first Israeli actress to do so. In February, Ayelet Zurer starred in an ad slamming the fur industry. Jewish actress and vegan Mayim Bialik has also appeared in PETA campaigns against eating meat.