BOSTON (CBS) — Researchers have found something surprising in Boston baby bottles.

According to a new study by Boston Medical Center, about 15 percent of 2-year-olds drink as much as four ounces of coffee a day.

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At the age of one year, between two and three percent of the infants studied were drinking coffee. At two years, that number grew to 15 percent — consuming on average a little more than an ounce of coffee a day.

“Our results show that many infants and toddlers in Boston – and perhaps in the US – are being given coffee and that this could be associated with cultural practices,” said Dr. Anne Merewood, director of the Breastfeeding Center at BMC and associate professor of pediatrics at Boston University School of Medicine.

There are no official guidelines for children’s coffee consumption, but there are some alarming potential health effects. The hospital said previous studies have shown that coffee and caffeine have been associated with depression, type 1 diabetes, sleep disturbances, substance abuse and obesity in children and adolescents.

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Another study found that 2-year-olds who drank coffee or tea had triple the risk of being obese in kindergarten, according to the hospital.

The study looked at 315 pairs of mothers and infants, and researchers said they were “surprised” to find that many mothers reported giving their babies coffee. Children of Hispanic mothers and mothers of baby girls were more likely to report the coffee consumption, the study found.

It’s not that uncommon for mothers in other countries to give children coffee, the hospital noted.

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“Given what the current data shows about the effects of coffee consumption among children and adolescents, additional research is needed to better determine the potential short and long-term health implications of coffee consumption among this younger age group in Hispanic and other populations,” Merewood said.