Is There a Link Between Coffee, Tea, and Leukemia?

Coffee May Contain Carcinogens, But Do They Pose a Cancer Risk?

coffee beans ground up then made into coffee
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If coffee or tea were shown to increase the risk of leukemia, a cancer of the white blood cells, this would be most unwelcome news to many people around the world. In the United States, coffee is second only to water as the most widely consumed beverage, and it’s the main source of caffeine among adults. Thus, the focus is on coffee here, but tea lovers should take heart that research is looking into both coffee and tea in regard to the risk of leukemia.

When Nature’s Bounty Isn’t Healthy

Let’s start by dispelling a myth: just because coffee is a natural product that comes from the earth, it doesn’t necessarily mean it is without risk. Hemlock is natural. Radon is a completely natural gas, yet it may contribute to many cases of lung cancer every year.

Some of the seemingly quasi-innocent items on the American Cancer Society’s “list of known human carcinogens” include the following:

  • alcoholic beverage
  • estrogen-progestogen therapy (combined)*
  • dust from leather
  • meat, when processed
  • fish, specifically when salted in the Chinese style

If any of these items are part of your life, remember that the absolute risk from a known carcinogen is important to keep in mind. That is, it's important to know how much an exposure to any given carcinogen increases your risk of cancer, in addition to simply knowing that a compound has the potential to increase that risk.

Another factor to consider is that, in your average cup of coffee, there is far more than caffeine, aroma, and flavor to contend with. A complex beverage, coffee actually contains hundreds of biologically active compounds, according to the report in a recent issue of the “Journal of the American College of Cardiology.” The same report noted that coffee consumption might actually be associated with reduced risk of type 2 diabetes and hypertension, as well as other conditions associated with cardiovascular risk such as obesity and depression, though these benefits have not been proven.

So, coffee is quite biologically active, and some of this activity may not be beneficial. What is more, even if coffee beans in their natural state harbored no human carcinogens, there would always be a theoretical possibility of carcinogens being introduced at some point during each of the many steps along the path from horticulture to the consumer’s cup:

  • planting and growth
  • picking and processing
  • packing, storing, trading, shipping, importing
  • roasting, grinding, and brewing

From Shrub to Café

What happens before your name is called and the barista produces your mocha late at the counter? The cup of coffee we drink today is derived from the seeds of Coffea arabica and/or Coffea canephora, after they have been processed and roasted. These plant species grow into shrubs or small trees whose fruit or seeds are an important export commodity in Central and South America, the Caribbean, and Africa.

These wonderful plants may be changing, however. Some of the oldest coffee varieties—much like heirloom tomato plants—are often susceptible to serious coffee diseases; when the plants are healthy, they produce high-quality seeds. Because of the increased susceptibility to disease, breeding programs are actively pursuing new genetic combinations, or cultivars, with improved disease resistance and good crop quality. In short, the chemical composition of coffee today, including potential carcinogens, may not be the chemical composition of coffee tomorrow.

The natural composition of the plant matter is just the beginning, however. After growth and harvesting, there are different processing methods used in the industry:

  • In dry processing, or natural processing, ripe coffee fruits are harvested and spread out over a surface such as cement patios or packed earth for drying. There they stay for 18 to 24 days. Once dried, the shriveled fruit portion is removed to produce what is known as parchment coffee; this product is then stored and later polished to remove the outside layer, making green coffee. Parchment coffee and green coffee seeds are stored in dry storage to minimize microbial activity prior to export and roasting.
  • In wet processing the fruit and pulp are pulled away from the seed from the get-go, with a slimy layer covering the seeds. The seeds are allowed to ferment for 24 to 72 hours in water at ambient temperatures. Microorganisms from the fruit, seed, handlers, water, and processing machinery can all factor in to the microbial equation, and have the potential to affect the coffee quality.

Wet-processed beans tend to produce a more acidic cup of coffee with less body, according to a report by Vaughan and colleagues recently published in “Applied and Environmental Microbiology.” The same report notes that a total of 215 named species of fungi and 106 species of bacteria have been found in association with coffee fruit and seed tissues.

Depending on the microbes involved, sometimes a substance called ochratoxin A (OTA) may contaminate the coffee. Both Aspergillus and Penicillium species are among those fungi capable of producing OTA, which is encountered very frequently and appears to be ubiquitous in coffee production, from fruit to roasting. The International Agency for Research on Cancer (IARC) has classified OTA as a possible human carcinogen.

Leukemia Risk From Coffee and Tea: The Italian Study

Thus, when investigators Stefano Parodi and colleagues found that the association between coffee intake and leukemia was unknown, they undertook a study to try to learn more. They were also interested in regular consumption of black tea and any association with the risk of leukemia.

This group used data from a large population in Italy, a country with a high coffee consumption and a low use of green tea. Participants from 11 Italian regions were interviewed, including 1,771 control patients and 651 individuals with leukemia. Associations between acute myeloid leukemia (AML), acute lymphoid leukemia, chronic myeloid leukemia (CML), chronic lymphoid leukemia, and use of coffee and tea were evaluated. The group adjusted for other things that could influence the risk of leukemia, such as gender, age, residence area, smoking, educational level, previous chemotherapy treatment, alcohol consumption, and other exposures including radiation and pesticides.

Results: No Apparent Link to Leukemia

This was a retrospective case-control study, which means you can find an association or link, but cannot say anything for sure regarding cause and effect. That said, results from this study were re-assuring for coffee lovers and black tea drinkers, alike.

No association was observed between regular use of coffee and any type of leukemia. In fact, this group reported a small protective effect of tea intake with respect to myeloid malignancies (AML and CML), which was more evident for AML. However, no clear dose-response relationship was found.

A Word From Verywell

Prior to this study, there had been some reports in small studies of lower risk of leukemia among regular coffee consumers. The present study did not find a reduction in risk, but on the other hand, it did not show any increased risk either.

It's an Individual Thing

Many benefits from regular coffee consumption have been proposed and seem likely, though are not proven definitively. One of the frequently theorized benefits is the role for coffee in preventing liver cancer. As with many things when it comes to dietary intake and consumption, the appropriateness of regular coffee consumption may be highly individual.

For instance, if you suffer from heartburn or acid reflux that is exacerbated by coffee, or maybe if caffeine sends your blood pressure skyward, or maybe you seem to be prone to heart rhythm abnormalities brought on by coffee and stress, then the daily dose of java may not be the best thing for you. Excessive coffee intake is also linked to a variety of disorders, not to mention poor sleep. And, from the perspective of malignancy, there is some evidence suggesting high consumption, more than 6.5 cups a day, might increase the risk of stomach cancer.

On the other hand, if you have been a regular coffee consumer for years and you thrive on your morning fix, in moderation, there may be benefits to be had—and there is no evidence that coffee increases your risk for leukemia. Moderation is key, and you need to follow the advice of your doctor in regard to any specific health conditions you may have.

Also, from the perspective of heart health and cardiovascular risk, if you are using cream and sugar, the lighter and sweeter you take your coffee, the more the potential risks of your coffee habit may offset any potential benefits.

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