Starbucks  has released a new line of olive oil-infused drinks that aim to be "velvety smooth, delicately sweet and lush" — but some customers have complained about stomach issues after consuming the new drinks.

Starbucks adds new olive oil-infused drinks to its menu

In February, Starbucks introduced a new line of "Oleato" drinks made with extra virgin olive oil in Milan. In March, the new drink line was rolled out to almost 600 stores throughout Seattle and Los Angeles.

The drinks, which include an oat milk latte, an ice shaken espresso with oat milk, and a golden foam cold brew, are all made with a spoonful of olive oil. According to Starbucks, the combination results in a "velvety smooth, delicately sweet and lush coffee that uplifts each cup with an extraordinary new flavor and texture."

Howard Schultz, Starbucks' founder and current interim CEO, said the Oleato drinks were inspired by his experiences in Italy with Italian coffee. "Oleato represents the next revolution in coffee that brings together an alchemy of nature's finest ingredients - Starbucks arabica coffee beans and Partanna cold-pressed extra virgin olive oil," he said.

Although some reviews of the Oleato drinks have been positive, some baristas and customers have reported stomach issues after trying one of the new drinks.

"Half the team tried it yesterday and a few ended up… needing to use the restroom, if ya know what I mean," wrote a user on  Reddit who claimed to be a current Starbucks barista. "I'm honestly scared to try it because I already have stomach/bowel problems"

"I've tried them, and tbh after drinking them honestly they just felt sick to my stomach lowkey," said another user on Reddit. "Like i had no appetite at all after that and that was the only thing I’ve had in the whole day."

Why are some customers experiencing stomach issues?

According to CNN, Starbucks' new Oleato drinks may have "a potentially fragile combination: caffeine, which is a stimulant, and olive oil, which is a relaxant."

Erin Palinski-Wade, a registered dietitian nutritionist (RDN), noted that mineral oils, including olive oil, are often used to treat constipation because they can help soften the stool, which makes it easier to go to the bathroom. In a 16-ounce coffee drink, there may be as much as 34 grams of fat, more than what is found in most meals.

"If you combined high fat in a meal or in a beverage along with coffee, which already stimulates the bowels, that combination can cause cramping," Palinski-Wade said. "It can cause increased mobility in the colon and therefore have that laxative effect."

In addition, many people drink coffee without eating anything to go with it, which may help the olive oil hit the digestive tract more quickly and lead to discomfort. "The effects may be more pronounced if you drink Oleato on an empty stomach," said Frances Largeman-Roth, another RDN.

Overall, the new Oleato drinks are "not going to make somebody physically ill from the standpoint of having a negative impact on health," Palinski-Wade said. "But more of that uncomfortable feeling of having to go to the bathroom or potentially cramping." (Maruf, CNN, 4/10; Lamour, TODAY/NBC News, 4/6; Reuters/Desai, Daily Mail, 4/6; Settembre, New York Post, 4/6)