In the fall of 2018, Jonah Peretti, chief executive of online publisher BuzzFeed, emailed a top official at Facebook Inc. The most divisive content that publishers produced was going viral on the platform, he said, creating an incentive to produce more of it.

He pointed to the success of a BuzzFeed post titled “21 Things That Almost All White People are Guilty of Saying,” which received 13,000 shares and 16,000 comments on Facebook, many from people criticizing BuzzFeed for writing it, and arguing with each other about race. Other content the company produced, from news videos to articles on self-care and animals, had trouble breaking through, he said.

Mr. Peretti blamed a major overhaul Facebook had given to its News Feed algorithm earlier that year to boost “meaningful social interactions,” or MSI, between friends and family, according to internal Facebook documents reviewed by The Wall Street Journal that quote the email.

BuzzFeed built its business on making content that would go viral on Facebook and other social media, so it had a vested interest in any algorithm changes that hurt its distribution. Still, Mr. Peretti’s email touched a nerve.

Facebook’s chief executive, Mark Zuckerberg, said the aim of the algorithm change was to strengthen bonds between users and to improve their well-being. Facebook would encourage people to interact more with friends and family and spend less time passively consuming professionally produced content, which research suggested was harmful to their mental health.

Within the company, though, staffers warned the change was having the opposite effect, the documents show. It was making Facebook’s platform an angrier place.

Company researchers discovered that publishers and political parties were reorienting their posts toward outrage and sensationalism. That tactic produced high levels of comments and reactions that translated into success on Facebook.

“Our approach has had unhealthy side effects on important slices of public content, such as politics and news,” wrote a team of data scientists, flagging Mr. Peretti’s complaints, in a memo reviewed by the Journal. “This is an increasing liability,” one of them wrote in a later memo.