TLDR;
This video discusses the evolving understanding of coffee's relationship to cancer risk. Initial concerns from the 1990s have largely been dispelled by more recent prospective studies.
- Coffee consumption is now associated with a lower overall risk of cancer, especially liver and endometrial cancers.
- The video addresses concerns about bladder and lung cancer, clarifying that these links are either unfounded or related to confounding factors like smoking.
- It concludes by cautioning against the consumption of very hot coffee due to the risk of esophageal and oral cancers, regardless of the beverage type.
Coffee possibly carcinogenic [0:00]
In 1991, the International Agency for Research on Cancer (IARC) classified coffee as possibly carcinogenic based on animal data and early human studies. These initial studies, which compared individuals with and without cancer, found no link to breast or colon cancer but suggested a possible association with bladder cancer. However, these case-control studies were considered weak due to inherent biases, as they assessed lifestyle factors after cancer diagnosis. The need for prospective studies, which follow cancer-free individuals over extended periods to observe cancer development in relation to coffee consumption, was recognized.
Newer studies [1:20]
Current research, including numerous prospective studies, indicates a lower overall cancer risk among coffee drinkers, particularly those with high consumption. On average, there's an 18% reduction in all types of cancer combined. This protective effect is most notable for liver and endometrial cancers, with a linear risk reduction observed up to about five or six cups of coffee per day.
Liver [1:34]
Coffee consumption is consistently linked to a lower risk of liver cancer, with approximately a 15% reduction in risk per daily cup and a 50% overall reduction in high consumers compared to low or non-consumers. This benefit appears linear up to five or six cups a day. Coffee's protective effects against insulin resistance, inflammation, and liver fat may contribute to this reduced risk, promoting overall liver health and lowering the risk of liver fibrosis and cirrhosis.
Endometrium [2:24]
Endometrial cancer, affecting the uterus's superficial layer, is also consistently found at lower rates in coffee drinkers, with a risk reduction that is linear up to about five or six cups daily. For other common cancers, the protective effect of coffee is less pronounced.
Colorectal [2:44]
For colorectal cancer, studies show either no link or a modest protective effect associated with coffee consumption. Coffee may reduce the risk of colorectal cancer by accelerating transit time in the intestine, which decreases the contact time between potential carcinogens in feces and the gut lining. The protective effects of coffee may be due to caffeine or other compounds, as some studies show a protective effect from decaf coffee, while others suggest caffeinated coffee has a stronger effect.
Breast [3:46]
Overall, coffee consumption shows no significant effect on breast cancer risk. However, there is some suggestion of a protective effect in specific groups, such as post-menopausal women. One proposed mechanism is that coffee contains phytoestrogens, plant-derived estrogen-like molecules that can act like estrogens in some tissues and have the opposite effect in others, similar to how soy is linked to a lower risk of breast cancer.
Others [4:16]
Most studies suggest a protective effect of coffee against prostate cancer, with about a 9-10% lower risk of both incidence and mortality. Some studies also indicate a protective effect against skin cancers like melanoma, potentially due to the antioxidant effects of polyphenols found in coffee. Coffee is a significant source of antioxidants in the American diet. For pancreatic cancer, there is no significant effect either way, and for less common cancers, the data remains inconclusive.
Bladder [5:57]
About 10 prospective studies on coffee and bladder cancer generally find no link either way. In 2016, the IARC reviewed a thousand studies on coffee and cancer and changed their stance, no longer considering coffee possibly carcinogenic. The data now suggests it might be protective for some cancers. While scientists are unlikely to reverse this conclusion, coffee is not recommended for individuals hypersensitive to caffeine. Pregnant women should moderate or avoid coffee due to links with low birth weight and pre-term birth.
Lung [7:02]
Early prospective studies suggested a link between coffee and a higher risk of lung cancer, but this association disappeared after adjusting for factors like smoking and BMI, which often correlate with coffee consumption. Acrylamide, formed during coffee roasting, is present in tiny levels, way below thresholds of concern.
One type causes cancer [7:40]
Very hot coffee, specifically above 65 degrees Celsius, is linked to a higher risk of esophageal and possibly oral cancer. This risk is due to the damage to cells in those tissues from the high temperature, not the coffee itself. Very hot drinks like tea or mate share this link. Allowing coffee to cool slightly is advisable to protect the tongue and esophagus.