Coffee doesn’t cause cancer, but these things might, according to the WHO

There isn’t enough proof to show a link between your morning cup of coffee and cancer risk, the World Health Organization said Wednesday.

The International Agency for Research on Cancer, or IARC, has downgraded its classification of coffee as a possible carcinogen. But it’s warning that drinking “very hot” beverages of any kind could potentially raise the cancer risk.

It’s pointing to certain countries, such as China, Iran and parts of South America, where teas are prepared at extremely high temperatures – above 65 or 70 C.

READ MORE: Does drinking coffee cause cancer? The World Health Organization doesn’t think so

The International Agency for Research on Cancer (IARC) is the WHO’s cancer research arm. Over the past few decades, it has studied more than 1,000 things, such as chemicals, food, and radiation to see if they could be tied to cancer risk.

There are five classifications – carcinogenic to humans, probably carcinogenic to humans, possibly carcinogenic to humans, not classifiable and probably not carcinogenic.

Dr. Paul Demers, who directs Cancer Care Ontario’s Occupational Cancer Research Centre, has participated in seven IARC evaluations on formaldehyde, night shift work, and a list of industrial chemicals, since the early 1990s.

He walked Global News through the five classifications and what they mean.

Group 1: Carcinogenic to humans

Prime examples: ionizing radiation, such as X-rays, UV tanning beds, asbestos, tobacco, formaldehyde and benzene, and processed meat as of 2015.

The IARC creates a team of about 20 to 30 experts who comb over all of the available evidence on a subject for about a year before coming to a conclusion.

“You need a whole lot of evidence pointing in this direction, including large studies of cancer in people that provides the most definitive evidence of increased cancer rates we can link to a specific chemical or other cause,” Demers said of the Group 1 category.

READ MORE: Are cellphones linked to cancer? What experts say about the possible risk

But keep in mind, just because you get an X-ray or eat processed meat, it doesn’t by any means equate to developing cancer.

“This isn’t an evaluation of the level of something that’s needed to cause cancer but if something can, overall, cause cancer or not,” Demers said.

With some carcinogens, one incident with major exposure, such as surviving an atomic bomb attack, could lead to developing cancer later on, while others may be concerned because of long-term exposure to certain chemicals while at work, Demers said as an example.

Group 2A: Probably carcinogenic to humans

Prime examples: Shift work, such as working overnights, certain pesticides, red meat, occupations such as hairdressing because of exposure to chemicals while dyeing hair, and creosote, a chemical used for treating wood to prevent rotting.

READ MORE: Are bagels and pasta really putting you at risk of lung cancer?

He focuses on workplace safety concerns, such as shift work and exposure to chemicals, and cancer risk. With shift work, for example, there are dozens of studies that warn of throwing off the body’s circadian rhythm, and disrupting hormone levels, elevating cancer risk.

“But still, the pattern isn’t strong enough to rule out other factors that could be at play that may be leading to these results. There’s quite a bit of evidence there, it just falls short from the overall conclusion,” Demers said.

Group 2B: Possibly carcinogenic to humans

Prime examples: Dry cleaning chemicals, gasoline engine exhaust, radio frequency radiation, such as WiFi.

The IARC classified 289 agents in this category. In this case, there are plenty of studies that point to some link, but they tend to be isolated to animal experiments and not in humans. In other cases, it’s too difficult to study in humans.

Coffee used to fall into this category before being downgraded to not classifiable.

Group 3: Not classifiable as to its carcinogenicity to humans

Prime examples: Cholesterol, tea, low frequency electric fields (energy generated by power lines), surgical implants like pacemakers, silicone breast implants, dental materials or ceramic implants, and highly refined mineral oils. Some industrial work, such as leather tanning and processing, and lumber and sawmill work fall into this category, too.

Coffee is now part of this category, along with Mate tea.

In this case, the evidence isn’t there to prop up any cancer concerns.

READ MORE: Is Splenda linked to cancer risk? Study ties sucralose to leukemia, tumours

“There is no consistent pattern, there’s not enough data and nothing to point in the direction of causing cancer,” Demers said.

Group 4: Probably not carcinogenic to humans

Prime example: Only one substance falls into this category – caprolactam.

There’s a reason why this list is so short. The IARC’s job is to study agents that are of concern to the public, not to verify the safety of every household chemical, Demers said.

“Things are forwarded to IARC not because they’re benign but because there is worry. There are a lot of resources that are poured into this evaluation, we don’t study things we don’t think there’s some kind of problem for,” he explained.

Read more about the IARC’s classifications here.

carmen.chai@globalnews.ca
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