Prevention of formation of important mutagens/carcinogens in the human food chain

A population-based prospective study of energy-providing nutrients in relation to all-cause cancer mortality and cancers of digestive organs mortality

The effect of dietary composition on mortality in low-income countries is largely unknown. We evaluated whether percentages of dietary energy derived from protein, fat and carbohydrates were associated with all-cause and cancer mortalities in a Bangladeshi population. Data from a prospective population-based cohort study of 17,244 men and women were used. Percentages of dietary energy derived from protein, fat and carbohydrates, assessed using a validated food-frequency questionnaire at baseline, were analyzed in relation to mortality over an average of 9 years (155,126 person-years) of follow-up. Cox proportional hazards regression models were used to estimate hazard ratios for all cause, all cancer and cancers of the digestive organs mortalities. Percentage of dietary energy from protein appeared to be significantly associated with cancer mortality. Fully adjusted hazard ratios for cancer mortality in increasing tertiles of percentage of dietary energy from protein were 1.0 (reference), 1.21 (0.73, 2.00) and 1.84 (1.08, 3.15) (p for trend = 0.023). These associations were much stronger for deaths from cancers of the digestive organs with fully adjusted hazard ratios in increasing tertiles of percentage of dietary energy from protein being 1.0 (reference), 2.25 (0.91, 5.59) and 4.85 (1.88, 12.51) (p for trend = 0.001). No significant associations in relation to cancer-related mortality were observed for percentage of dietary energy from fat. Novel findings from this prospective study show protein is an important risk factor or proxy to an important risk factor for cancer mortality especially from digestive organ cancers in Bangladesh.

Role of fried foods and oral/pharyngeal and oesophageal cancers

We investigated the role of fried foods on oral-pharyngeal and oesophageal cancers, using data from two case–control studies conducted in Italy and Switzerland between 1992 and 1999, one with a total of 749 (634 men) cases of oral/pharyngeal cancer and 1772 (1252 men) controls, the other with 395 (351 men) cases of oesophageal cancer and 1066 (875 men) controls. Controls were admitted for acute, non-neoplastic conditions, unrelated to alcohol and smoking consumption. After allowance for sex, age, centre, education, body mass index, tobacco smoking, alcohol drinking and nonalcohol energy intake, the multivariate odds ratios (ORs) for an increment of one portion per week of total fried foods were 1.11 (95% confidence interval (CI): 1.05–1.17) for oral-pharyngeal and 1.16 (95% CI: 1.08–1.26) for oesophageal cancer. The ORs were consistent across strata of gender (OR in men only were 1.10 and 1.16, respectively), age, alcohol, tobacco consumption and body mass index.

Inhibition of carcinogenesis by minor anutrient constituents of the diet

A continuing study of chemopreventive agents has focused on several categories of naturally occurring compounds that inhibit carcinogen activation and are effective in preventing carcinogen-induced neoplasia when administered at short time-intervals before carcinogen challenge. The inhibitory compounds are: aromatic isothiocyanates found in cruciferous vegetables, monoterpenes present in citrus fruits and caraway-seed oil, and organosulphur compounds occurring in Allium species. Preliminary work indicates that glucobrassicin and indoles existing in cruciferous vegetables also have these attributes. Almost all carcinogens that are consumed in food require metabolic activation. Thus, inhibition of carcinogen activation reactions could be effective against this type of exposure. In addition, three naturally occurring compounds, i.e. phenethyl isothiocyanate, D-limonene and dipropyl sulphide inhibit activation of the tobacco-specific carcinogen NNK, and accordingly may have the capacity to diminish carcinogenic response to exposures to tobacco. The property of cruciferous vegetables, orange oil, benzyl isothiocyanate, and D-limonene, to act as both blocking and suppressing agents has been discussed. Two possible mechanisms for this multi-phase activity were presented. The first is that these inhibitory substances activate a complex integrated defence mechanism against toxic compounds which entails both blocking and suppressing components. The blocking component is the initial line of defence, and the suppressing component constitutes a 'fail-safe' backup to assure that if any of the toxic material attacks cellular constituents, its effects will be nullified. The second possible mechanism considered is that the inhibitors, because of high reactivity, have multiple biological effects that are separate and not part of a single, coordinated response. Inhibitors that have both blocking and suppressing effects could be particularly useful as chemopreventive agents. A simple interim classification of foods in terms of their potential impact on the occurrences of cancer has been proposed.