Lecture 11: Food, Alcohol and cancer Flashcards
what are the methodological challenges of research involving food and alcohol and cancer?
Randomised control trials are problematic:
- they are difficult or impossible
- ethical dilemmas (unethical to expose people to harmful levels of alcohol)
- poor quality evidence
the measures of exposure of often a self-report
prospective studies need to be large and long, so retrospecive studies are challenged
vested interests:
- food and alcohol industry is powerful
how can we measure ‘usual intakes’ of food?
- food frequency questionnaire
- dietary habits
- 24h diet recall (multiple pass methods) - go to peoples homes and asked what they ate yesterday
- weighed diet record
- biomarkers - urine and blood
- food balance sheets (food and agriculture organisation)
what types of exposure can be used in food studies?
studies need to be clear about what the exposure is
if the exposure if nutrients:
- helps us understand biology and intake across all foods
- people don’t consume nutrients, they consume food
if the exposure is food:
- this is more practical as it is able to be translated into public health advice
- able to integrate nutrient and non-nutrient effects
- but not all foods are created equally (e.g. yogurt)
if the exposure is dietary patterns:
- this represents intake in real life
- but it is difficult to attribute associatins to single foods/nutrients
- may have complex beneficial/harmful effects
- exposure depends on the research questions
what types of studies are useful for food research?
ecological and cross sectional studies:
- population surverys: NHANES, NZ Adult and Children’s Nutrition Surveys
- Population level data
- Food balance sheets and rates (Food and Agriculture Organisation of the UN)
- National nutrition surveys (NZ hasn’t done one since 2008)
what does this show?
this is the national nutrition survey of japan 1955-1993
found important changes over this time
- mortality of stomach cancer decreased for men
- lung cancer, colon cancer increased over time
- an increase in milk, meat, oil and dat intake
- decrease in rice and carbohydrate intake
- increase fat, calcium and vitamin A
- used to support other data and studies
what are blue zone?
they are longevity hotspots
- places where people live longest (into 90s)
- california, costa rica, sardinia, greece and okinawa
- found that they eat minimally processed food and have an active lifestyle
- they eat mostly plants, especially beans and legumes
- eat less meat in small portions
what is an example of a case control study used for food?
- Case control studies are problemation as you start with outcome of interest but cancer develops over long period of time and people find it hard to remember what they ate in the past
- this case control study looked at the povision of school milk was exposure of interest.
- used it as a proxy for high milk intake and risk of colerectal cancer
- Found that particpation in school milk found reduction in the risk of colorectal cancer
what is an example of a cohort study used for food?
- the problem with cohort studies is that they need to be long and large as cancer is a rate outcome, but it is very expensive and labour intensive
- good example is the EPIC study - european prospective investigation into cancer and nutrition:
- multicentre prospective study 1992
- looked at 23 centres in 10 european countries (denmakr, france, germany, greece, italy, netherlands, norway, spain, sweden, UK
- 500,000 participants aged 35-70 years who didnt have cancer
- they had repeated and detailed dietary assessments and biomarkers
- examined a wide range of exposures and outcomes
what does this show?
eating more fibre is associated with a decreased risk of colorectal cancer
- is a protective factor
- they also recruited many vegetarians as a dietary pattern of interest
what RCTs have been used to research food and cancer?
RCTs are problematic but are good for investigating dietary supplements
good example is a study investigation Vitamin C and E intake via supplements to prevent prostate cancer and total cancer
- no evidence that the supplements reduce these cancers
- this is a 10 year RCT, but needed this length if looking to chronic disease outcomes like cancer
what did the World Cancer Research Fund and American Institute for Cancer Research do?
released 3 reports in 1997, 2007 and 2018 showing food, nutrition and cancer relationship.
- they examined diet and lifestyle factors
- and looked at nutrients, energy intake, alcohol and physical activity in the development of the cancer process
how did the World Cancer Research Fund and American Institute for Cancer Research judge the evidence?
they had an evidence matrix with very strict criteria for what comprise strong evidence, limited evidence and convincing, probable evidence.
Predefined requirements for determining grading of evidence:
- number and types of studies
- quality of exposure and outcome assessment
- heterogeneity within and between study types
- exclusion of chance, bias or confounding
- biological gradient
- evidence of mechanisms
- size of effect
what did the World Cancer Research Fund and American Institute for Cancer Research do with their graded findings?
they made a matrix showing which risk factors increased or decreased the risk of different types of cancers
what recomendations came from the World Cancer Research Fund and American Institute for Cancer Research?
- be a healthy weight
- be physically active
- eat a diet rich in wholegrains, vegetables, fruit and beans
- limit consumption of fast foods, other processed foods high in fat starches or sugars
- limit consumption of red and processed meat
- limit consumption of sugar sweetened drinks
- limit alcohol consumption
- don’t use supplements for cancer
- breastfeed you baby if you can
- after a cancer diagnosis, follow our recommendations if you can
what is the new framework policy that came from this research?
- policy framework for a healthy population by making public health recommendations:
Behaviour change communication:
- education and skills
- counselling in healthcare
- inform people
Systems change:
- integrate actions across sections (involve government)
health enhancing environments:
- improve good and drink supply
- labelling and packaging
- marketing restrictions
- policies
- healthy urban designs
what does this show?
there is a linear association between alcohol consumption and cancer (for multiple types of cancer)
what does this show?
alcohol is a very important risk factor world wide
- alcohol is estimated to have caused around 500,000 deaths from cancer in 2012. this is equivalent to 5.8% of cancer deaths world-wide.
how is alcohol and cancer involved in alcohol-attributable deaths?
this data shows that alcohol-attributable deaths is 23% due to cancer in men, and 44% in women.
however, its not just cancer, injury is mostly alcohol-attributable death
