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Nutrition 3701


CANCER- Lecture 12-  8 October 2010




Outline for the day



            Epidemiologic Investigation of Diet and Cancer Relationships

            Specific aspects of diet

                        Energy balance, growth rate, and body size

                        Dietary fat and meat intake

                        Fruits and vegetables

                        Dietary fibre

                        Alcohol and Caffeinated beverages

                        Carcinogens and foods

                        Vitamin supplements







Epidemiologic Investigation of Diet and Cancer Relationships


            -concepts of incidence and prevalence


            -two critical questions-what are the important dietary factors in cancer

-what is the nature of the dose response relationships

                        - what are the important dietary factors- how would one determine these?

-dose- response- a product in food could prevent or promote cancer but not

be present in food in sufficient amounts to prevent or promote cancer


-in terms of prevention it may be that a human diet has sufficient amounts of molecule or molecules required to achieve the maximal preventative impact


-in that case (sufficient amounts of a molecule or molecules) there is not potential for reducing cancer rates by altering intake amounts of the molecule in question


-important thing is to identify that sub-population in the overall population that is consuming to much of a toxin or too little of a preventative molecule


-a variety of epidemiological approaches can be taken to investigate cancer and diet relationships


-such cancer/diet relationships can be evaluated by collecting data on dietary intake (eg food frequency questionnaires), by using biochemical indicators of dietary intake( but none exist for useful indicator such as total fat, sodium or fibre) or by measuring body size and composition


-diet-gene interactions are also helpful studies-how?



            Specific aspects of diet

                        Energy balance, growth rate, and body size

-in animals studies there is a link between caloric restriction and reduction of mammary gland cancer


-hard to assess the link between caloric restriction and reduction of mammary gland cancer in free-living populations because in free-living populations most of variability in energy intake is due variable energy expenditure


-taller women have a greater risk of breast cancer than shorter women


-growth rate- early menarche is a risk factor for breast cancer in humans


-accumulation of  adipose tissue correlated with endometrial in women and gall bladder cancer and colon cancer in women and men (men when abdominal circumference is taken into consideration)

-prior to menopause women with greater adipose tissue accumulation tend to have a lower risk of breast cancer


-after menopause there is a positive but weak correlation with breast cancer



                        Dietary fat and meat intake

-dietary fat intake is controversial but generally the recommendation is to keep the percentage of total calories represented by fat to < 30 %



-red meat associated with increased colon cancer


                        Fruits and vegetables


                                                -4-10 servings per day is the model today


-lung, stomach and colon cancer are the standouts in this area- i.e. lower cancer rates in those consuming 4-10 servings per day


-constituents of these foods causing cancer prevention is not clear but carotenoids, folic acid vitamin C and phytoestrogens and fibre have been fingered



                        Dietary fibre

-low rates of cancer in areas of Africa where fibre consumption and stool bulk is high


                                                -reasons proposed for lower cancer rates


-speeding of carcinogens through the colon   -binding of carcinogens

                                                            -altering colonic flora (pre-biotics)

                                                            -reducing the pH


-serving as a substrate for the generation of short chain fatty acids that are preferred substrate for colonic epithelial cells


-scraping of cells


-high fibre intakes associated with countries where obesity and meat intake is less and physical activity is high- so it it really the fibre reducing cancer?


                        Alcohol and caffeinated beverages


-alcohol associated with increased risk of oral cavity, larynx, esophagus and liver and breast cancer


-regarding breast cancer alcohol tends to induce higher estrogen levels which are associated with breast cancer


-coffee contains a range of mutagens and these mutagens have be fingered as the causative association


                        Carcinogens and foods

-aflatoxins and other mycotoxins-produced by fungi- induces mutations


-plant origin carcinogens

            -pyrrolizdine alkaloids

                    -found in some herbal remedies (eg coltsfoot for coughs)

-hydrazines –found in  commonly cultivated edible mushrooms

-carcinogenic in animal studies


-nitrites in foods-preservatives

                            -converted to nitrosamines by acid in the body

-nitrates in vegetables converted to nitrites in our bodies

-nitrosamines are carcinogenic and mutagenic


-heating produces polycyclic aromatic hydrocarbons and heterocyclic amines-charred biscuits and steaks


-increased salt- associated with gastric cancer


                        Vitamin supplements


-high intakes of vitamins C and E have not been associated with reductions of breast cancer incidence


-vitamin E supplementation associated with reduced risk of oral cancer


-in a region of China where vegetable intakes are low,  supplements of b-carotene E and selenium reduced the incidence of gastric cancer





Evening primrose oil- GLA related decreased angiogenesis and increasing anti mobility agent maspin


Liver nerve and pancreatic cancer have been studied but generally EPO is not as effective as traditional pharmaceuticals