diet and cancer Flashcards
What is cancer?
Uncontrolled cell division, cells fail to differentiate, tumours develop
CAUSE
Mutation or loss of gene which is passed onto subsequent generations of cells
Rarely- genetic defects inherited however sporadic
Risk increases with age (errors increase, repair capacity decreases)
Usually environmental, always genetic
How are insights into cancer studied?
Early insights from migration studies
People who’ve migrated into a country
Changes in risk of developing various diseases
Suggests environmental factors are in play
What are some lifelong influences on cancer risk?
Diet Infection Smoking Medication Physical activity
What are methods to study cancer?
Human studies-
~epidemiological studies
~intervention studies- however difficult to implement as takes course over decades, would need vast nos and people wouldn’t comply
Animal studies-
~in vivo studies (typically rats/mice)
~regulated and licensed
~induce cancer, can be genetically manipulated
Cellular models-
~in vitro studies (cell cultures)
-primary cell lines (isolated directly from humans, limited no of cell division, so short term)
-immortalised cell lines (cells derived from tumours)
Are immortalised cell lines useful?
Can add cell function at molecular level Quick, cheap Can easily look at range of doses Unlimited divisions and quantity of cells Genetically identical cells
However,
Can’t see interaction w other cells
Specialised tissue function might be lost
Differ from primary cells due to multiple divisions
Are animal studies useful?
Relatively short lived so can monitor diet within months
Easy to control
Tissues readily available
Can be genetically manipulated
However,
Ethical concerns
Can’t replicate environment/lifestyle
No animal can replicate complexities of a human
How are human study designs done?
Epidemiological- ~ecological ~cross sectional ~cohort pro/retrospective ~case-control
Experimental
~RCTs
What is nutritional epidemiology?
Studies that produce evidence of an association between two variables
Focuses on associations between diet and disease or risk factor for disease
However, diet is complex
Multifactorial
Observational studies
What is an ecological study?
Disease freq is correlated w disease exposure in a population based study
Population is defined by time, geography or socio economic status
Useful to generate hypotheses and there’s a large no of subjects
However, info not necessarily collected for disease association
At population level data- no evidence of individual disease v exposure
Other confounding factors
What is a cross-sectional study?
Measure nutritional exposure and disease state in individuals
Relates individual exposure to disease
However, difficult to determine relationship between exposure and outcome, cause or consequence
Factors affecting disease survival may bias results
Not useful
What is a case control study?
Individuals w disease/outcome are compared to randomly selected control group from non-diseased population
Efficient, quick, cheaper than cohort or clinical trial
However, representative? Biased? Disease may alter behaviour
Some use
What is a cohort study?
Cohort followed over time and rate of disease development observed in relation to exposure
Prospective- follows disease development
Retrospective- uses measures of past exposure
Unbiased, no recall bias, measure of exposure precedes disease
However, confounding factors, large sample size required, very long
Very useful
What are experimental studies?
Individuals randomly assigned to receive treatment/placebo
Specific, prospective, strictly controlled, small population size, randomised, double blind, confounding factors randomly distributed
However, v costly, ethical concerns, drop out and short follow up
Useful but difficult, bio markers needed
What decreases the risk of cancer?
Physical activity
Whole grain foods w dietary fibre
Non-starchy vegetables
Fruit
What increases the risk of cancer?
Body fatness Adult weight gain Fatty/processed foods Starches, sugars Red meat Processed meat Alcoholic drinks
