Dr. Ron’s Research Review – June 15, 2011

This week’s research review focuses on coffee and cancer.

A recent study published in the Journal of the National Cancer Institute found a strong inverse association between coffee consumption and risk of lethal prostate cancer. The association appears to be related to non-caffeine components of coffee. (Wilson, Kasperzyk et al. 2011)

A meta-analysis of epidemiological studies published in British Journal of Urology International found no evidence to support a harmful effect of coffee consumption on prostate cancer risk. (Park, Myung et al. 2010)

A meta-analysis of cohort studies published in BMC Cancer concluded that coffee consumption may reduce the total cancer incidence and it also has an inverse association with some type of cancers. (Yu, Bao et al. 2011)

An article published in Cancer Science concluded that there is substantial evidence to show that cancers of the colon, liver, and pancreas are associated with insulin resistance, and that these cancers can be prevented by increasing physical activity, and possibly coffee consumption. (Tsugane and Inoue 2010)

Dr. Ron


Articles

Roasted coffees high in lipophilic antioxidants and chlorogenic acid lactones are more neuroprotective than green coffees

            (Chu, Brown et al. 2009) Download

Oxidative stress is involved in many neurodegenerative processes leading to age-related cognitive decline. Coffee, a widely consumed beverage, is rich in many bioactive components, including polyphenols with antioxidant potential. In this study, regular and decaffeinated samples of both roasted and green coffee all showed high hydrophilic antioxidant activity in vitro, whereas lipophilic antioxidant activities were on average 30-fold higher in roasted than in green coffee samples. In primary neuronal cell culture, pretreatment with green and roasted coffees (regular and decaffeinated) protected against subsequent H(2)O(2)-induced oxidative stress and improved neuronal cell survival (green coffees increased neuron survival by 78%, compared to 203% by roasted coffees). All coffee extracts inhibited ERK1/2 activation, indicating a potential attenuating effect in stress-induced neuronal cell death. Interestingly, only roasted coffee extracts inhibited JNK activation, evidencing a distinctive neuroprotective benefit. Analysis of coffee phenolic compounds revealed that roasted coffees contained high levels of chlorogenic acid lactones (CGLs); a significant correlation between CGLs and neuroprotective efficacy was observed (R(2) = 0.98). In conclusion, this study showed that roasted coffees are high in lipophilic antioxidants and CGLs, can protect neuronal cells against oxidative stress, and may do so by modulation of the ERK1/2 and JNK signaling pathways.

Coffee consumption and risk of prostate cancer: a meta-analysis of epidemiological studies

            (Park, Myung et al. 2010) Download

OBJECTIVE: To evaluate the association between coffee consumption and the risk of prostate cancer. METHODS: We searched PubMed, EMBASE, and the bibliographies of relevant articles in August 2009. Two evaluators independently reviewed and selected articles based on predetermined selection criteria. RESULTS: Twelve epidemiological studies (eight case-control studies and four cohort studies) were included in the final analysis. In a meta-analysis of all included studies, when compared with the lowest level of coffee consumption, the overall relative risk (RR) of prostate cancer for the highest level of coffee consumption was 1.16 (95% confidence interval [CI] 1.01-1.33). In subgroup meta-analyses by study design, there was a significant positive (harmful) association between coffee consumption and prostate cancer risk in seven case-control studies using both crude and adjusted data (RR 1.20, 95% CI 1.02-1.40; and RR 1.21, 95% CI 1.03-1.43, respectively), whereas there was no significant association in four cohort studies using crude or adjusted data (RR 0.97, 95% CI 0.68-1.38; and RR 1.06, 95% CI 0.83-1.35, respectively). CONCLUSION: Given that a cohort study gives a higher level of evidence than a case-control study, there is no evidence to support a harmful effect of coffee consumption on prostate cancer risk. Further prospective cohort studies are required.

Insulin resistance and cancer: epidemiological evidence

            (Tsugane and Inoue 2010) Download

Over the last 60 years, Japanese people have experienced a rapid and drastic change in lifestyle, including diet. Suspicions have been raised that so-called 'Westernization', characterized by a high-calorie diet and physical inactivity, is associated with increasing trends in the incidence of cancer of the colon, liver, pancreas, prostate, and breast, as well as type 2 diabetes. Epidemiological evidence from our prospective study, the Japan Public Health Center-based Prospective (JPHC) study, and systematic literature reviews generally support the idea that factors related to diabetes or insulin resistance are associated with an increased risk of colon (mostly in men), liver, and pancreatic cancers. These cancers are inversely associated with physical activity and coffee consumption, which are known to decrease the risk of type 2 diabetes. The suggested mechanism of these effects is that insulin resistance and the resulting chronic hyperinsulinemia and increase in bioavailable insulin-like growth factor 1 (IGF1) stimulate tumor growth. In contrast, associations with diabetes are less clear for cancer of the colon in women, and breast and prostate, which are known to be related to sex hormones. The effect of insulin resistance or body fat on sex-hormone production and bioavailability may modify their carcinogenic effect differently from cancers of the colon in men, and liver and pancreas. In conclusion, there is substantial evidence to show that cancers of the colon, liver, and pancreas are associated with insulin resistance, and that these cancers can be prevented by increasing physical activity, and possibly coffee consumption.

Coffee Consumption and Prostate Cancer Risk and Progression in the Health Professionals Follow-up Study

            (Wilson, Kasperzyk et al. 2011) Download

Background Coffee contains many biologically active compounds, including caffeine and phenolic acids, that have potent antioxidant activity and can affect glucose metabolism and sex hormone levels. Because of these biological activities, coffee may be associated with a reduced risk of prostate cancer. Methods We conducted a prospective analysis of 47 911 men in the Health Professionals Follow-up Study who reported intake of regular and decaffeinated coffee in 1986 and every 4 years thereafter. From 1986 to 2006, 5035 patients with prostate cancer were identified, including 642 patients with lethal prostate cancers, defined as fatal or metastatic. We used Cox proportional hazards models to assess the association between coffee and prostate cancer, adjusting for potential confounding by smoking, obesity, and other variables. All P values were from two-sided tests. Results The average intake of coffee in 1986 was 1.9 cups per day. Men who consumed six or more cups per day had a lower adjusted relative risk for overall prostate cancer compared with nondrinkers (RR = 0.82, 95% confidence interval [CI] = 0.68 to 0.98, P(trend) = .10). The association was stronger for lethal prostate cancer (consumers of more than six cups of coffee per day: RR = 0.40, 95% CI = 0.22 to 0.75, P(trend) = .03). Coffee consumption was not associated with the risk of nonadvanced or low-grade cancers and was only weakly inversely associated with high-grade cancer. The inverse association with lethal cancer was similar for regular and decaffeinated coffee (each one cup per day increment: RR = 0.94, 95% CI = 0.88 to 1.01, P = .08 for regular coffee and RR = 0.91, 95% CI = 0.83 to 1.00, P = .05 for decaffeinated coffee). The age-adjusted incidence rates for men who had the highest (>/=6 cups per day) and lowest (no coffee) coffee consumption were 425 and 519 total prostate cancers, respectively, per 100 000 person-years and 34 and 79 lethal prostate cancers, respectively, per 100 000 person-years. Conclusions We observed a strong inverse association between coffee consumption and risk of lethal prostate cancer. The association appears to be related to non-caffeine components of coffee.

Coffee consumption and risk of cancers: a meta-analysis of cohort studies

            (Yu, Bao et al. 2011) Download

BACKGROUND: Coffee consumption has been shown to be associated with cancer of various sites in epidemiological studies. However, there is no comprehensive overview of the substantial body of epidemiologic evidence. METHODS: We searched MEDLINE, EMBASE, Science Citation Index Expanded and bibliographies of retrieved articles. Prospective cohort studies were included if they reported relative risks (RRs) and corresponding 95% confidence intervals (CIs) of various cancers with respect to frequency of coffee intake. We did random-effects meta-analyses and meta-regressions of study-specific incremental estimates to determine the risk of cancer associated with 1 cup/day increment of coffee consumption. RESULTS: 59 studies, consisting of 40 independent cohorts, met the inclusion criteria. Compared with individuals who did not or seldom drink coffee per day, the pooled RR of cancer was 0.87 (95% CI, 0.82-0.92) for regular coffee drinkers, 0.89 (0.84-0.93) for low to moderate coffee drinkers, and 0.82 (0.74-0.89) for high drinkers. Overall, an increase in consumption of 1 cup of coffee per day was associated with a 3% reduced risk of cancers (RR, 0.97; 95% CI, 0.96-0.98). In subgroup analyses, we noted that, coffee drinking was associated with a reduced risk of bladder, breast, buccal and pharyngeal, colorectal, endometrial, esophageal, hepatocellular, leukemic, pancreatic, and prostate cancers. CONCLUSIONS: Findings from this meta-analysis suggest that coffee consumption may reduce the total cancer incidence and it also has an inverse association with some type of cancers.


References

Chu, Y. F., P. H. Brown, et al. (2009). "Roasted coffees high in lipophilic antioxidants and chlorogenic acid lactones are more neuroprotective than green coffees." J Agric Food Chem 57(20): 9801-8.

Park, C. H., S. K. Myung, et al. (2010). "Coffee consumption and risk of prostate cancer: a meta-analysis of epidemiological studies." BJU Int 106(6): 762-9.

Tsugane, S. and M. Inoue (2010). "Insulin resistance and cancer: epidemiological evidence." Cancer Sci 101(5): 1073-9.

Wilson, K. M., J. L. Kasperzyk, et al. (2011). "Coffee Consumption and Prostate Cancer Risk and Progression in the Health Professionals Follow-up Study." J Natl Cancer Inst.

Yu, X., Z. Bao, et al. (2011). "Coffee consumption and risk of cancers: a meta-analysis of cohort studies." BMC Cancer 11: 96.