Abstract
There is evidence that diet and nutrition are modifiable risk factors for several cancers, but associations may be flawed due to inherent biases. Nutritional epidemiology studies have largely relied on a single assessment of diet using food frequency questionnaires. We conduct an umbrella review of meta-analyses of observational studies to evaluate the strength and validity of the evidence for the association between food/nutrient intake and risk of developing or dying from 11 primary cancers. It is estimated that only few single food/nutrient and cancer associations are supported by strong or highly suggestive meta-analytic evidence, and future similar research is unlikely to change this evidence. Alcohol consumption is positively associated with risk of postmenopausal breast, colorectal, esophageal, head & neck and liver cancer. Consumption of dairy products, milk, calcium and wholegrains are inversely associated with colorectal cancer risk. Coffee consumption is inversely associated with risk of liver cancer and skin basal cell carcinoma.
Highlights
The percentage of nominally significant meta-analyses ranged from 0% for gallbladder cancer to 74% for head and neck cancer (Table 2) and from 0% for legumes/soy products to 54% for alcohol and 67% for grains (Supplementary Data 4)
AThis report presents results for cancers of mouth, pharynx, larynx, and upper aerodigestive tract. bSmall study bias is based on the P value from the Egger’s regression asymmetry test and the random-effects summary estimate was larger compared to the point estimate of the largest study in a meta-analysis. cExcess significance bias is based on the P value of the excess significance test using the largest study in a meta-analysis as the plausible effect size
Head and neck cancer had the largest proportion of meta-analyses with high heterogeneity (40%) that was substantially reduced after excluding a pooling project of case–control studies, whereas gallbladder cancer had no meta-analysis with high heterogeneity followed by CRC and stomach cancer with 20% each (Table 2)
Summary
Data was extracted from the WCRF Third Expert Report[2], which is one of the most rigorous and systematic analysis of the scientific research on the associations of diet, nutrition, adiposity, and physical activity with risk of cancer development and survival. The WCRF systematic review for cervical cancer was published in 2018 but did not include meta-analyses for dietary variables and was excluded from the current paper[48]. The relevant umbrella reviews for prostate and endometrial cancer[49] have been published separately[50], and WCRF meta-analyses for pancreatic and ovarian cancers were conducted in 2011 and 201351,52 and were considered outdated and not included in the current assessment. More details on the literature search strategy, search terms, and inclusion/exclusion criteria of the WCRF CUP reports are provided in Supplementary Information
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