CANCER- Lecture 12- 8 October 2010
DIET, PREVENTION OF CANCER, AND TREATMENT OF CANCER
PREVENTION OF CANCER
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
TREATMENT OF CANCER
PREVENTION OF CANCER
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 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
-dilution,
-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
TREATMENT OF 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