Kombucha tea is a fermented drink made with tea, sugar, bacteria and yeast. To make the drink, bacteria and yeast must first grow together to form a culture. The culture is added to the sugar and tea. Then the mix is allowed to ferment. The end result is a liquid that has vinegar, B vitamins and many other types of acids, including amino acids.

Supporters claim that kombucha tea helps prevent and treat health conditions, from blood pressure to cancer. There is limited data on kombucha tea. A small amount of research suggests that kombucha tea may give benefits similar to probiotic supplements. For example, some research suggests kombucha tea may support a healthy immune system and prevent constipation.

But there are few valid medical studies of kombucha tea's role in human health. And there are risks to think about.

Kombucha tea has caused stomach upset, infections and allergic reactions in some people. Kombucha tea is often made (brewed) in homes under unclean conditions. This makes it likely that bad bacteria can grow.

Also, when the tea is made with ceramic pots that have lead in them, lead poisoning happens. The acids in the tea cause lead to leak from the ceramic glaze.

In short, there isn't enough proof that kombucha tea has the health benefits that some claim. At the same time, cases of harm have been reported. People who are pregnant or breastfeeding or who have weakened immune systems should avoid kombucha tea. Others may drink the tea if they like the taste, but only if it comes from a trusted source.