Sweet risks: Lead to kidney stones—bubble tea’s dark side

They’ve become as common on British high streets as coffee shops – bubble tea outlets offering colourful, Instagram-worthy drinks in endless flavour combinations. The Taiwanese beverage, a mix of black tea, milk, sugar, and chewy tapioca pearls, has captured global imaginations since its 1980s origins. But recent findings suggest this beloved treat may deserve closer scrutiny.

A Consumer Reports investigation in the US found high lead levels in some bubble tea products, echoing earlier concerns about cassava-based foods. The pearls – those signature “bubbles” – are made from cassava starch, and the root readily absorbs lead and other heavy metals from contaminated soil. (No UK testing has been released.)

Contamination isn’t the only worry. Tapioca pearls’ starchy composition can slow digestion or, in severe cases, cause blockages – conditions that bring nausea, vomiting and abdominal pain. People with already sluggish digestion are most vulnerable. Even guar gum, a common thickener, may contribute to constipation if consumed frequently.

Bubble tea’s effects extend to kidney health. In 2023, Taiwanese doctors removed over 300 kidney stones from a 20-year-old woman who reportedly drank bubble tea instead of water. High oxalate and phosphate levels can promote stone formation, though such extreme cases likely stem from excessive consumption.

For children, the risks can be immediate. The pearls present a choking hazard well known to paediatricians. Adults are not exempt either: in Singapore, a 19-year-old woman reportedly died after inhaling pearls through a partially blocked straw, while another survived thanks to quick-thinking bystanders.

Bubble tea’s sugar load raises long-term health concerns. Most varieties contain 20–50g of sugar, as much or more than a can of Coca-Cola (35g). A Taiwanese study found nine-year-olds who regularly drank bubble tea were 1.7 times more likely to have cavities in their permanent teeth.

In California, the drink has been cited as contributing to the youth obesity epidemic, though many young adults remain unaware of the risks. Its combination of sugar and fat heightens the likelihood of type 2 diabetes, obesity and metabolic disease, while prolonged consumption may promote fatty liver disease. These effects mirror those of any high-sugar product that spikes blood glucose and drives fat storage in the liver.

Surprisingly, bubble tea may also affect mental well-being. Studies in China have linked frequent consumption to higher rates of anxiety and depression in children. Similar trends appear in adults: research among Chinese nurses found regular bubble tea drinkers reported more anxiety, depression, fatigue, and job burnout, along with lower well-being. Lower consumption correlated with fewer suicidal thoughts, though causation remains unclear.

Doctors have even spotted tapioca pearls on medical scans of patients admitted for unrelated emergencies such as car accidents or appendicitis. The pearls, visible throughout the digestive tract, sometimes cause diagnostic confusion because they appear as dense, stone-like objects.

This doesn’t mean bubble tea should be banned. But it may be wise to treat it as an occasional indulgence rather than a daily ritual. And if you do partake, skip the straw – drinking directly from the cup offers more control and lets your senses brace for those chewy surprises.

The Conversation