A man in Taiwan suffered severe kidney damage after developing a daily habit of drinking coffee brewed from stale beans, mistakenly believing that boiling them in hot water would make them safe to consume.
The case was shared by Dr Hung Yung-Hsiang, a nephrologist at a hospital in Taipei, in a Facebook post highlighting the hidden dangers of consuming expired food products.
According to Dr Hung, the patient — a 50-year-old man surnamed Lee — led a generally healthy lifestyle. He exercised regularly, went on morning runs, avoided alcohol and had no known underlying medical conditions.
Lee’s only daily beverage was black coffee, which he brewed using coffee beans purchased at discounted prices. Unknown to him, the beans had gone stale.
Towards the end of 2025, Lee began noticing unusual symptoms, including excessive foam in his urine and swelling in both ankles. Believing these signs were caused by over-exercising, he initially ignored them.
However, his condition worsened when he suddenly collapsed during a morning run and was rushed to hospital. Medical tests revealed that his estimated glomerular filtration rate (eGFR) had fallen below 10, leading to a diagnosis of stage five kidney disease, the most severe stage of kidney failure.
Dr Hung said he was initially puzzled as to how an otherwise healthy individual could develop such serious kidney problems. The cause became clear only after Lee revealed that he had been using stale coffee beans to brew his daily coffee, as he did not want to waste them.
Dr Hung explained that stale coffee beans may contain ochratoxin A, a toxin produced by certain moulds. The substance is known to target the kidneys and can also be found in other foods such as cereals, beer, wine, nuts and dried fruits.
Crucially, ochratoxin A does not break down easily under high temperatures and can survive typical cooking or brewing processes. Dr Hung noted that the toxin only decomposes at temperatures above 280°C — far higher than water’s boiling point of 100°C.
Lee had assumed that boiling the beans would eliminate any harmful substances, but this proved ineffective.
Dr Hung advised the public to avoid consuming expired or stale food products and warned against stockpiling food solely to save money. He also recommended storing opened items such as coffee beans in airtight containers and keeping them refrigerated to slow spoilage.
