California’s new coffee cancer warning no more than a tempest in a teapot

Europeans have their daily wine, Asians their tea, but it has been estimated that the primary source of dietary antioxidants for the average American is coffee. An impressive lineup of scientific articles attests to coffee’s health benefits, but in March 2018 a California judge ruled that coffee roasters and retailers will have to post a cancer warning label. According to a group called The Council for Education and Research on Toxics, a chemical calledacrylamide that forms in trace amounts during roasting is potentially carcinogenic. Citing a law passed in 1986 known as Proposition 65, they sued Starbucks and dozens of other companies. Despite a lack of evidence that acrylamide levels in coffee are enough to cause harm in humans, Los Angeles Superior Court Judge Elihu Berle ruled for the plaintiffs. In so doing, he ran counter to guidance from the World Health Organization, which officially dropped coffee from its list of possible carcinogens in 2016.  The WHO’s determination was based on a review of more than 1,000 studies by its International Agency for Research on Cancer. Even “Dr. Danger” Bob Arnot, who had spent years reporting on the risks of coffee as a medical correspondent for NBC and CBS, reversed course and proclaimed “coffee is the new red wine” and dubbed it “the healthiest new superfood.”

Why coffee is a health food

Studies consistently find that coffee drinkers live longer and have lower rates of mental decline, diabetes, and heart disease.[1]As with wine, there is a J-shaped curve: health benefits up to a certain level of daily consumption, then the opposite. (With coffee the curve is flatter, due to less upside risk of heavy consumption compared to wine.)  One of the larger studies, called the Iowa Women’s Health Study, tracked a cohort of nearly 42,000 postmenopausal women aged 55-69 at enrollment and followed for 15 years. Coffee drinkers who consumed 1-3 cups per day on were on average about 25% less likely to die of cardiovascular disease, with the effect diminishing at 4 cups or greater. Coffee-derived polyphenol antioxidants were credited for the effect. And despite the newly mandated warnings, coffee consumption is associated with lower risk of most types of cancers.[2]Even when evaluating dietary acrylamide consumption specifically, amounts in coffee appear too low to have any measurable impact on cancer risk.[3]
Acrylamide occurs in similar levels in roasted barley and is found in breads, meat, and potato products. It is formed during the roasting process, a result of what is called the Maillard reaction, in which amino acids from proteins combine with sugars to give browned foods their distinctive flavor. But in the case of coffee, the roasting process also increases the antioxidant capacity of the brewed extract.[4]This is reminiscent of wine production, where polyphenols increase and develop along with alcohol during fermentation.
With both coffee and wine however, the benefits are not attributable to the antioxidant polyphenols alone. Alcohol factors in as a net positive in the right amounts with wine, and caffeine is at least part of the reason for java’s rejuvenating effects. For diabetes, there is a benefit with both decaf and regular, but for prevention of Alzheimers and other forms of age-related mental decline it appears that caffeine is involved.[5]
Other than requiring unnecessary expenditure of millions of dollars–money that could be spent on effective cancer prevention strategies–the new law is unlikely to have much effect. I suspect that even the lawyers and plaintiffs in the case haven’t banished their daily brew. But there is a downside to actions like this: they foster consumer cynicism and mistrust of health authorities. Exaggerating a risk too small to measure by invoking new regulations is dismissed as just another buzzkill. We would do well to remember that it was coffee that ushered in the Age of Reason; modern science, enlightened rationality, democracy, and capitalism all came to light in the coffee houses of the 18thcentury. We could use a bit of enlightenment now! See you at Starbucks . . .


[1]O’Keefe JH1, DiNicolantonio JJ2, Lavie CJ3. Coffee for Cardioprotection and Longevity. Prog Cardiovasc Dis. 2018 Feb 21. pii: S0033-0620(18)30039-2.
[2]Wierzejska R1. Coffee consumption vs. cancer risk – a review of scientific data. Rocz Panstw Zakl Hig. 2015;66(4):293-8.
[3] Kotemori A1, Ishihara J2, Zha L3, Liu R3, Sawada N1, Iwasaki M1, Sobue T3, Tsugane S1; JPHC Study Group. Dietary acrylamide intake and risk of breast cancer: The Japan Public Health Center-based Prospective Study. Cancer Sci. 2018 Mar;109(3):843-853.
[4]Priftis A, Stagos D, Konstantinopoulos K, Tsitsimpikou C, Spandidos DA, Tsatsakis AM, Tzatzarakis MN, Kouretas D.
Comparison of antioxidant activity between green and roasted coffee beans using molecular methods. Mol Med Rep. 2015 Nov;12(5):7293-302.
[5]Panza F1, Solfrizzi V, Barulli MR, Bonfiglio C, Guerra V, Osella A, Seripa D, Sabbà C, Pilotto A, Logroscino G. Coffee, tea, and caffeine consumption and prevention of late-life cognitive decline and dementia: a systematic review. J Nutr Health Aging. 2015 Mar;19(3):313-28.

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