A U.K. zoo says it has stopped feeding bananas, and other fruit, to its monkeys, instead giving the primates more vegetables. (Rajesh Kumar Singh/Associated Press)

Monkeys at a zoo in England have been banned from eating bananas — for their own good. 

Bananas, and other fruits, are bad for the monkeys' health and can rot their teeth, according to staff at Paignton Zoo in Devon.

"They simply are much more sugary than the sort of fruits that monkeys would have access to in the wild," said Amy Plowman, the zoo's head of conservation and advocacy.

The monkey's high sugar diet led to problems similar to those seen in humans, namely tooth decay, diabetes, and issues related to obesity, such as heart problems.

"What we found is that the monkeys are maintaining a much healthier weight, which is really good. In zoos, animals tend to perhaps put on a little more weight than they should because they've got very easy access to lots of food and they don't as much exercise as in the wild," she said.

A low-sugar diet also slightly improves the animals' behaviour, especially among smaller monkeys, who tend in live in packs and tend to squabble a bit, she added.

So what are the monkeys eating now? More vegetables, particularly the green, leafy kind, which are packed with nutrients and take the animals longer to eat. Plowman said.

Bristol Zoo has followed the lead of Paignton​ Zoo in cutting back on the fruit in the diet of its monkeys.