Physical activity has been associated with lower risks of breast and colorectal cancer in epidemiological studies; however, it is unknown if these associations are causal or confounded. In two-sample Mendelian randomisation analyses, using summary genetic data from the UK Biobank and GWA consortia, we found that a one standard deviation increment in average acceleration was associated with lower risks of breast cancer (odds ratio [OR]: 0.51, 95% confidence interval [CI]: 0.27 to 0.98, P-value = 0.04) and colorectal cancer (OR: 0.66, 95% CI: 0.48 to 0.90, P-value = 0.01). We found similar magnitude inverse associations for estrogen positive (ER^+ve) breast cancer and for colon cancer. Our results support a potentially causal relationship between higher physical activity levels and lower risks of breast cancer and colorectal cancer. Based on these data, the promotion of physical activity is probably an effective strategy in the primary prevention of these commonly diagnosed cancers.

Background: Body weight and body mass index (BMI) are positively related to risk of colon cancer in men, whereas weak or no associations exist in women. This discrepancy may be related to differences in fat distribution between sexes or to the use of hormone replacement therapy (HRT) in women. Methods: We used multivariable adjusted Cox proportional hazards models to examine the association between anthropometric measures and risks of colon and rectal cancer among 368 277 men and women who were free of cancer at baseline from nine countries of the European Prospective Investigation Into Cancer and Nutrition. All statistical tests were two-sided. Results: During 6.1 years of follow-up, we identified 984 and 586 patients with colon and rectal cancer, respectively. Body weight and BMI were statistically significantly associated with colon cancer risk in men (highest versus lowest quintile of BMI, relative risk [RR] = 1.55, 95% confidence interval [CI] = 1.12 to 2.15; P_trend = .006) but not in women. In contrast, comparisons of the highest to the lowest quintile showed that several anthropometric measures, including waist circumference (men, RR = 1.39, 95% CI = 1.01 to 1.93; P_trend = .001; women, RR = 1.48, 95% CI = 1.08 to 2.03; P_trend = .008), waist-to-hip ratio (WHR; men, RR = 1.51, 95% CI = 1.06 to 2.15; P_trend = .006; women, RR = 1.52, 95% CI = 1.12 to 2.05; P_trend = .002), and height (men, RR = 1.40, 95% CI = 0.99 to 1.98; P_trend = .04; women, RR = 1.79, 95% CI = 1.30 to 2.46; P_trend <.001) were related to colon cancer risk in both sexes. The estimated absolute risk of developing colon cancer within 5 years was 203 and 131 cases per 100 000 men and 129 and 86 cases per 100 000 women in the highest and lowest quintiles of WHR, respectively. Upon further stratification, no association of waist circumference and WHR with risk of colon cancer was observed among postmenopausal women who used HRT. None of the anthropometric measures was statistically significantly related to rectal cancer. Conclusions: Waist circumference and WHR, indicators of abdominal obesity, were strongly associated with colon cancer risk in men and women in this population. The association of abdominal obesity with colon cancer risk may vary depending on HRT use in postmenopausal women; however, these findings require confirmation in future studies.

Alcohol consumption may be associated with risk of colorectal cancer (CRC), but the epidemiological evidence for an association with specific anatomical subsites, types of alcoholic beverages and currentvs.lifetime alcohol intake is inconsistent. Within the European Prospective Investigation into Cancer and Nutrition (EPIC), 478,732 study subjects free of cancer at enrolment between 1992 and 2000 were followed up for an average of 6.2 years, during which 1,833 CRC cases were observed. Detailed information on consumption of alcoholic beverages at baseline (all cases) and during lifetime (1,447 CRC cases, 69% of the cohort) was collected from questionnaires. Cox proportional hazard models were used to examine the alcohol‐CRC association. After adjustment for potential confounding factors, lifetime alcohol intake was significantly positively associated to CRC risk (hazard ratio, HR = 1.08, 95%CI = 1.04–1.12 for 15 g/day increase), with higher cancer risks observed in the rectum (HR = 1.12, 95%CI = 1.06–1.18) than distal colon (HR = 1.08, 95%CI = 1.01–1.16), and proximal colon (HR = 1.02, 95%CI = 0.92–1.12). Similar results were observed for baseline alcohol intake. When assessed by alcoholic beverages at baseline, the CRC risk for beer (HR = 1.38, 95%CI = 1.08–1.77 for 20–39.9vs.0.1–2.9 g/day) was higher than wine (HR = 1.21, 95%CI = 1.02–1.44), although the two risk estimates were not significantly different from each other. Higher HRs for baseline alcohol were observed for low levels of folate intake (1.13, 95%CI = 1.06–1.20 for 15 g/day increase) compared to high folate intake (1.03, 95%CI = 0.98–1.09). In this large European cohort, both lifetime and baseline alcohol consumption increase colon and rectum cancer risk, with more apparent risk increases for alcohol intakes greater than 30 g/day.