Munching on large amounts of phytoestrogen-rich leaves from the Milletia dura tree appears to alter hormone levels and behavior among red colobus monkeys, according to a study published in the journal Hormones and Behavior.
Studying a group of male red colobus monkeys in Uganda, scientists from the University of California-Berkeley found that levels of estradiol and cortisol rose with seasonally higher consumption of estrogen-like compounds. In addition, the monkeys fought and mated more, and indulged less in the social-bonding activity of grooming.
“It’s one of the first studies done in a natural setting providing evidence that plant chemicals can directly affect a wild primate’s physiology and behavior by acting on the endocrine system,” said study lead author Michael Wasserman, who conducted the research as a graduate student at UC Berkeley’s Department of Environmental Science, Policy and Management. “By altering hormone levels and social behaviors important to reproduction and health, plants may have played a large role in the evolution of primate — including human — biology in ways that have been underappreciated.”
Researchers warned against assigning too much influence to phytoestrogens, however, explaining that diet is just one factor in behavior. Others include the hormones already produced inside the body as well as the amount of competition for food and mates.