The hidden hazard in that piping-hot cup of tea

For decades, the international medical community pointed to coffee as a major cause of cancer. But our research in Linxian, China three decades ago pointed in a completely different direction

At the time, I was working at the National Cancer Institute (NCI). We chose to conduct our studies on esophageal cancer in Linxian, China because its people were very malnourished, lacking adequate levels of several micronutrients. They also had high rates of esophageal cancer (thankfully rare in the U.S.). So we knew we could observe fairly quickly whether nutritional supplementation would prevent cancer in these people.

Since they were deficient in several vitamins, we actually developed a “factorial design” for the study that allowed us to look at the effects of the different vitamins together, separately, and in various combinations.

This approach got around the dictum of having to study only one vitamin at a time, as if they were drugs. The new factorial design also allowed us to approximate something closer to a real diet.

The effects of the nutritional supplements in China were so dramatic, they reduced overall cancer rates in the entire population and improved general measures of health and nutritional status in the entire community.

But remember — we also wanted to determine why esophageal cancer rates were so high in the first place.

At the time, we felt the evidence pointed to the temperature of their beverages. In fact, people in China drank beverages at very hot temperatures, whether tea or simply hot water (a popular beverage especially in the colder months). You see, heat damages the lining of the upper GI tract, leading to proliferation of cells to repair and replace the damage. This response probably contributes to the promotion of cancer — and may even damage cellular DNA leading to initiation of cancer.

Unfortunately, the International Agency for Research on Cancer (IARC), part of the World Health Organization, didn’t really buy into our theory. Instead, in 1991, they classified drinking coffee as possibly causing cancer. That incorrect recommendation stood for years, while mountains of evidence piled up on the health benefits of coffee.

Today, IARC is catching up with the science. And it turns out, we were on the right track about beverage temperatures…

Let your hot tea and coffee cool off before drinking it

A group of 23 scientists recently reviewed all evidence on esophageal cancer in the journal Lancet Oncology. The studies reviewed came from China, Iran, Turkey, and South America where they traditionally drink tea or mate (a popular South American herbal infusion) at very hot temperatures (70 degrees C, or 158 degrees F).

The researchers concluded that hot temperatures DO cause an increased risk of esophageal cancer. Furthermore, the hotter the beverage temperature, the greater the esophageal cancer risk. In addition, they concluded that drinking coffee or mate itself is not a risk factor if consumed at a cooler temperatures.

In light of this new evidence, the IARC finally reversed its stance and now accepts the finding that drinking very hot beverages is probably a cause of cancer in humans. Not coffee itself, as they so vigorously stated back in the 1990s.

Indeed, many studies since the 1990s show no increased risk of cancer from coffee drinking. On the contrary, they show reduced risks of liver and uterine cancer. I recently reported on studies showing coffee dramatically reduces the risk of colon cancer as well.

I doubt many people outside of China, Iran and Turkey, and parts of South America drink beverages that are uncomfortably hot. But in any event, when boiling water for tea or herbal infusions, make sure the liquid cools down to a comfortable temperature before you drink it. You will avoid getting burned and getting upper GI cancers. (And McDonald’s and Starbucks can avoid those frivolous lawsuits from people who can’t handle their drinks!)

Meanwhile, we can see what other health recommendations IARC/WHO has to change as the evidence accumulates over the next quarter-century, like the low-fat myth we reported earlier this week.



“Cancer Risks from very hot drinks, but not coffee or mate,” Medscape ( 6/15/2016