Hot-brewed coffee has higher levels of antioxidants than cold brew, which are believed to be responsible for some of the health benefits of the popular drink, a study has found.

The study, published in the journal Scientific Reports, also found that the pH levels or acidity indicator, of both hot and cold coffee were similar, ranging from 4.85 to 5.13 for all coffee samples tested.

Coffee companies and lifestyle blogs have tended to tout cold brew coffee as being less acidic than hot coffee and thus less likely to cause heartburn or gastrointestinal problems, said researchers from Thomas Jefferson University in the US.

While the popularity of cold brew coffee has soared in recent years -- the US market grew 580 per cent from 2011 to 2016 -- the researchers found almost no studies on cold brew, which is a no-heat, long-steeping method of preparation.

At the same time, there is well-documented research that hot-brewed coffee has some measurable health benefits, including lower risk of some cancers, diabetes and depression.

While the overall pH levels were similar, the researchers found that the hot-brewed coffee method had more total titratable acids, which may be responsible for the hot cup's higher antioxidant levels.

"Coffee has a lot of antioxidants, if you drink it in moderation, research shows it can be pretty good for you. We found the hot brew has more antioxidant capacity," said Megan Fuller, an assistant professor at Thomas Jefferson University.

Considering hot and cold brews have comparable pH levels, researchers said, coffee drinkers should not consider cold brew a "silver bullet" for avoiding gastrointestinal distress.