Which Is Healthier, Dark or Medium Roast Coffee?
By Adin Smith, MS | Posted July 31, 2021
New research suggests that dark roast coffee is a healthier choice over medium or light alternatives.Kolb H, Kempf K, et al. Health Effects of Coffee: Mechanism Unraveled? Nutrients. 2020 Jun 20;12(6):1842.
Here are the three main differences in health benefits between coffee roasts.
1) Dark roast coffee has more potent antioxidant effects
One study compared the effects of light roast vs. dark roast coffee on participants’ vitamin E and glutathione blood levels.Kotyczka C, Boettler U, et al. Dark roast coffee is more effective than light roast coffee. Mol Nutr Food Res. 2011 Oct;55 (10):1582-6.
Glutathione is considered a master antioxidant involved in recycling vitamins E and C, tissue reparation, and immune health. Vitamin E is also a powerful antioxidant that plays an essential role in cell membrane health.
In this comparison study, participants consumed two cups of dark roast coffee per day for a month, then switched over to drinking light roast coffee for another month.
Upon trial completion, the results showed that dark roast coffee consumption was more effective at increasing blood levels of antioxidants vitamin E and glutathione.
2) DNA protection
Our cells have protective systems to help guard against toxins that may cause harm.Ma Q. Role of nrf2 in oxidative stress and toxicity. Annu Rev Pharmacol Toxicol. 2013;53:401-426. But not all toxins are harmful. Oddly enough, we need some amounts to function optimally.Finkel T. Signal transduction by reactive oxygen species. J Cell Biol. 2011;194(1):7-15.
Many plant compounds, including those found in coffee, are “helpful toxins” that create mild cellular stress that activates protective systems within our cells.Qin S, Hou DX. Multiple regulations of Keap1/Nrf2 system by dietary phytochemicals. Mol Nutr Food Res. 2016 Aug;60(8):1731-55.
Therefore, stimulating these systems may provide wide-reaching health effects, limiting DNA damage and increasing antioxidant levels.Hochkogler C, Schweiger K. Daily consumption of a dark-roast coffee for eight weeks improved plasma oxidized LDL and alpha-tocopherol status. J Funct Foods. 2019 May;56:40-48. ,Bakuradze T, Boehm N, et al. Antioxidant-rich coffee reduces DNA damage, elevates glutathione status and contributes to weight control. Mol Nutr Food Res. 2011 May;55(5):793-7.
Each cell in the body incurs at least ten thousand DNA-damaging events daily.Ames BN, Shigenaga MK, et al. Oxidants, antioxidants, and the degenerative diseases of aging. Proc Natl Acad Sci U S A. 1993 Sep 1;90(17):7915-22. If your cells can keep up with their natural repair process, they can maintain their proper DNA structure.
However, excessive DNA-damaging substances caused by environmental toxins (i.e., air pollution) or internal toxins produced from within the body may have unhealthy consequences.
Fortunately, evidence suggests that certain compounds found in coffee may help protect against DNA damage.
Dark roast coffee drinkers had up to 27% less DNA damage
In a four-week study, researchers measured the effects of drinking three cups of dark roast coffee per day vs. a water equivalent on DNA damage.Bakuradze T, Lang R, et al. Consumption of a dark roast coffee decreases the level of spontaneous DNA strand breaks: a randomized controlled trial. Eur J Nutr. 2015 Feb;54(1):149-56.
At trial completion, results showed that individuals assigned to the dark roast group had 27% less DNA damage than the water control group.
Similarly, another study published a few years later found dark roast drinkers had 23% less DNA damage compared to the control group.Schipp D, Tulinska, et al. Consumption of a dark roast coffee blend reduces DNA damage in humans: results from a 4-week randomized controlled study. Eur J Nutr 2019 Dec;58(8):3199-3206.
Light roast coffee appears to have a weaker effect on DNA damage
One study showed that drinking light roast coffee compared to a water equivalent for five days decreased markers of DNA damage by roughly 12%—which was about half the potency of dark roast studies.Mišík M, Hoelzl C, et al. Impact of paper filtered coffee on oxidative DNA-damage: results of a clinical trial. Mutat Res. 2010 Oct 13;692(1-2):42-8.
Furthermore, an eight-week study measuring the effects of drinking 3-5 cups of light roast coffee vs. a water equivalent on DNA damage did not show a significant protective effect.Shaposhnikov S, Hatzold T, et al. Coffee and oxidative stress: a human intervention study. Eur J Nutr. 2018 Mar;57(2):533-544.
3) Cellular defense
Dark roast coffee contains higher amounts of the compounds responsible for activating the body’s cellular defense mechanisms.
When roasting coffee beans, a compound known as trigonelline gets converted to N-methylpyridinium (NMP), a potent activator of the Nrf2 antioxidant defense system.Boettler U, Volz N, et al. Coffees rich in chlorogenic acid or N-methylpyridinium induce chemopreventive phase II-enzymes via the Nrf2/ARE pathway. Mol Nutr Food Res. 2011 May;55(5):798-802.
In contrast, lightly roasted beans have lower amounts of NMP, and may not activate antioxidant defenses as strongly.
To make matters worse for light roast, it has higher amounts of trigonelline—a compound that is known to interfere with such defenses.Boettler U, Sommerfeld K, et al. Coffee constituents as modulators of Nrf2 nuclear translocation and ARE (EpRE)-dependent gene expression. J Nutr Biochem. 2011 May;22(5):426-40.
Overall, any coffee roast type appears to offer health benefits but considering this new research, dark roast coffee may be the best choice for optimal health.
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