coffee and decreased colon cancer

an interesting case-control study found that coffee consumption is associated with a decreased risk of colorectal cancer CRC (see coffee and dec colon cancer cancerepidem2016 in dropbox, or Cancer Epidemiol Biomarkers Prev. 2016; 25(4): 634). details:

--5145 colorectal cancer (CRC) cases were compared with 4097 controls from the Molecular Epidemiology of Colorectal Cancer (MECC) study, a population-based study in northern Israel, beginning in 1998.

--mean age 70, 52% male, 60% Ashkenazi/20% Sephardi/13% Arab, 7% first-degree relative with CRC, 58% consuming >= 5 vege servings/d, 35% "sports activity", 10% current/29% former smokers, 25% daily aspirin, 74% colon/23% rectal cancer). mean coffee intake in controls was 2.0 servings/d. there were significant differences in both quantity and types of coffee drunk by the different ethnic groups

--results, comparing coffee drinkers to nondrinkers:

    --coffee consumption was associated with 26% lower odds of developing CRC [OR 0.74; (0.64–0.86), p<0.001], controlling for known risk factors (age, sex, ethnicity, vegetable consumption, sports participation, statin use, daily low-dose aspirin, smoking status and family history). additional controlling for total daily liquid consumption or total calorie consumption did not significantly affect these results.

        --decaffeinated coffee had 18% lower odds [OR 0.82 (0.68–0.99), p=0.04]

        --boiled coffee had 18% lower odds [OR, 0.82 (0.71–0.94), p=0.004].

    --there was a dose-response curve, with p<0.001 for the trend. compared to <1 serving/day:

        --intake of 1 to <2 servings/day had 22% lower odds for developing CRC [OR 0.78 (0.68–0.90), p< 0.001]

        --2 to 2.5 servings/day had 41% lower odds [OR 0.59 (0.51–0.68), p<0.001]

        ​-->2.5 servings/day had 54% lower odds [OR, 0.46 (0.39–0.54) p< 0.001]

    ​--also, there was an overall inverse relationship between CRC and vegetable consumption (p<0.001), daily low-dose aspirin (p=0.03)​, sports participation (p<0.001), and direct relationship with smoking status (p<0.001), and sex (p<0.001).

so, a bright spot for me given my coffee consumption. but does this all make sense?

--coffee has many bioactive components, including chlorogenic acids (powerful anti-oxidants, which modify gene expression and inhibit DNA methyltransferase), polyphenols (which have anti-oxidant and antiproliferative effects, and induce cell-cycle arrest in colorectal cell lines), melanoidins (which may increase colon motility), diterpenes (which may be anticarcinogenic by enhancing defense systems against oxidative stress), and caffeine (may also be anti-oxidant, and limit growth of human colon cancer cells). the actual effects of these constituents is not so clear in humans, since much of the above is through in vitro analyses.

--coffee also reduces bile acid secretion

--coffee also modifies the microbiome: there are some data from small human experiments that coffee does change the fecal microbiome favorably, increasing Bifidobacterium spp. Another study, presented only as an abstract, looked at the microbiome of coffee consumers in an effort to see how coffee might lower the risk of diabetes, finding in rats that those on high fat diet had less weight gain and less insulin resistance, and more lactobacillus in their microbiome (FASEB journal; 2013; 27:951)​

--and, coffee does change some bowel functions, such as increasing intestinal motility and stool output

--though, it should be added that there are some differences in the above components, depending on the actual coffee beans used, the degree of roasting, and the brewing technique

--and, although the epidemiologic data are not entirely consistent, most suggest the above association (eg, see Public Health Nutrition 2013; 16: 346, a meta-analysis finding an overall 15% reduction in colon but not in rectal cancer, especially in Europe and in women), and several show a decreased incidence of liver cancer. of note in the Israeli study, there was a lower incidence of both colon and rectal cancer, though less impressive for rectal cancers.

--this study did look at aspirin consumption, which is associated with lower colon cancer risk (see: http://gmodestmedblogs.blogspot.com/2015/09/low-dose-aspirin-and-colon-cancer-risk.html ), but did not assess NSAID use, also associated in many studies with lower risk of colon cancer

--though a case-control study can never be definitive, the constellation of biological plausibility, the consistency with other observational studies, the magnitude of the effect, and the dose-response curve (the more coffee, the better) tends to support the conclusion. there could, however, be reverse causation: did those with GI symptoms from an early cancer, for example, stop drinking coffee?  it would really be hard to have a real randomized controlled study, where thousands of people were randomized to drinking varying amounts of coffee and followed for 5-10 years. so, these case-control studies are about as good as we can get....

for relevant blogs, see:

http://gmodestmedblogs.blogspot.com/2015/11/drink-coffee-and-live-longer.html  reporting on the Nurses' Health Studies, finding a decrease in total mortality in coffee-drinkers

http://gmodestmedblogs.blogspot.com/2015/03/coffee-and-decreased-coronary-artery.html , a Korean observational study, finding a pretty strong association between coffee-drinkers and decreased coronary artery calcifications

there are also several blogs in the BMJ website on chocolate (another personal addiction), also rich in polyphenols. one showed clinical improvement in those with peripheral artery disease (see http://gmodestmedblogs.blogspot.com/2014/07/dark-chocolate-helps-with-periph.html )