WEEK 4: Diet and cancer Flashcards
: What is cancer and how does it arise?
A: Cancer is a genetic disease, which means it results from changes in the DNA of cells. However, it is not necessarily inherited.
Cancer arises when somatic cells (non-reproductive cells) acquire mutations that give them a growth advantage, leading to uncontrolled cell division and tumor formation.
Q: What factors can promote cancer development and progression?
A: Cancer development and progression can be promoted by:
*Anything that causes mutations in cellular DNA.
*Anything that prevents the correction or removal of mutations in cellular DNA.
Q: How can dietary constituents affect cancer risk?
- Mutagenic Chemicals:
Some dietary constituents may contain mutagenic chemicals or may be converted to mutagenic chemicals by gastrointestinal (GIT) enzymes or commensal flora (the normal bacteria in the gut). - Protective Actions:
Some dietary constituents may protect against or remove mutagenic chemicals present in food or formed in the GIT. - Transit Time:
Dietary constituents may increase the transit time through the GIT, reducing the time for mutagenic chemicals to form or exert their effects, thereby providing a protective mechanism.
Q: Can you explain how dietary constituents might protect against cancer?
A: Yes, dietary constituents can protect against cancer in two main ways:
By neutralizing or removing mutagenic chemicals that are either present in the food or formed in the GIT.
By increasing the transit time through the GIT, which reduces the exposure time of the gut lining to potential mutagenic chemicals, decreasing the likelihood of these chemicals causing mutations in cellular DNA.
Q: How significant are modifiable lifestyle factors in the development of cancer?
A: Modifiable lifestyle factors play a major role in the aetiology of many cancers. According to Cancer Research UK, approximately 38% of total cancers are avoidable through changes in lifestyle.
Q: What are the most preventable types of cancer, and what are their prevention rates?
The most preventable types of cancer, according to Cancer Research UK, include:
Lung cancer: 80% preventable.
Laryngeal cancer: 70% preventable.
Stomach cancer: 54% preventable.
Bowel cancer: 54% preventable.
How do dietary constituents specifically affect the prevention of stomach and bowel cancers?
A: Dietary constituents play a significant role in the prevention of stomach and bowel cancers:
For bowel cancer, 13% of cases are attributed to the consumption of processed meats, around 6% to alcohol consumption, and 28% to a diet low in fiber.
The prevention rates for these cancers are largely due to the impact of diet on their development and progression.
Q: What are some key dietary changes that can help reduce the risk of bowel cancer?
A: Key dietary changes that can help reduce the risk of bowel cancer include:
Reducing the intake of processed meats.
Limiting alcohol consumption.
Increasing dietary fiber intake.
Q: How many new cancer cases in the USA in 2015 were attributed to dietary causes according to the 2019 study?
Q: How many of these cases were directly attributable to diet, and how many were associated with obesity?
Q: Which type of cancer had the highest proportion of cases attributed to dietary causes?
A: The 2019 study estimated that 80,000 new cancer cases in the USA diagnosed in 2015 were attributed to dietary causes.
A: Of the 80,000 cases, 67,500 were directly attributable to diet, while 12,500 were associated with obesity.
A: Colorectal cancers (CRC) had the highest proportion, with 52,225 cases, accounting for 38% of CRC cases.
Q: What dietary factors contributed significantly to new cancer cases, and how many cases were associated with each factor?
Q: Which demographic groups were more at risk for diet-related cancer cases?
Q: Why is it important to consider these dietary factors in cancer prevention strategies?
A: Significant dietary factors and their associated cases were:
Low dietary consumption of whole grains: 27,700 cases.
Low consumption of dairy products: 17,700 cases.
High intakes of processed meats: 14,500 cases.
A: Men, particularly those in the middle age range of 45-64 years, were more at risk than women. Additionally, Hispanics and blacks were more at risk than Caucasians.
A: Considering these dietary factors in cancer prevention strategies is crucial because a significant number of cancer cases could be prevented through dietary modifications.
By increasing whole grain and dairy consumption and reducing processed meat intake, the incidence of diet-related cancers, particularly colorectal cancer, can be significantly reduced. Furthermore, targeted interventions can be designed for high-risk demographic groups to effectively mitigate their risk.
Q: What is the Continuous Update Project (CUP)?
Q: How does the Continuous Update Project help in cancer research?
A: The Continuous Update Project (CUP) is an initiative that collects and analyzes all published information about nutrition and cancer worldwide. This information is made freely available online, and expert panels periodically assess it to make recommendations about diet and the strength of evidence.
A: The CUP helps in cancer research by providing a centralized, comprehensive database of the latest research on nutrition and cancer.
This enables researchers and health professionals to access up-to-date information, facilitating informed recommendations and interventions.
Q: Who evaluates the information collected by the Continuous Update Project?
Q: When was the latest report by the expert panels of the Continuous Update Project released?
Q: Why is the Continuous Update Project important for public health?
A: Expert panels periodically assess the information collected by the CUP. These panels review the latest research and make recommendations about diet and the strength of the evidence linking nutrition to cancer.
A: The latest report by the expert panels of the Continuous Update Project was released in 2018.
A: The CUP is important for public health because it:
-Provides evidence-based dietary recommendations to reduce cancer risk.
-Keeps healthcare professionals and the public informed about the latest findings in nutrition and cancer research.
-Helps shape public health policies and dietary guidelines to promote cancer prevention.
Which cancers are influenced by diet?
Most obviously diet will influence cancers of the GIT, so cancers of the mouth, oesophagus, stomach, small intestine, colon and rectum will be expected to be affected. Cancers of associated organs, such as liver and pancreas are also heavily influenced.
However cancers arising in airways structures – larynx, bronchi and lungs - also seem to be influenced by dietary factors: Cancer causing chemicals can be picked up from the GIT into the blood stream and into the urine so diet may well influence non-GIT cancers.
The EPIC study has investigated dietary influences on most common forms of cancer though associations with non-GIT cancers are usually not so strong as those in the GIT.
Which dietary constituents produce cancer causing mutations?
The dietary material most implicated in cancer causation is meat, especially red meat and processed meat – ham, bacon, salami etc. which is treated with preservatives. White meat, such as chicken and fish seems to be much less of a problem.
The major problem is that constituents in meat are converted to nitroso compounds by gut bacteria and these compounds are the mutagenic chemicals.
As well as being produced within the GIT and thereby affecting it, the nitroso compounds can be taken up into the blood circulation and can cause cancers elsewhere.
What are the sources of nitroso compounds?
Preserved meat such as bacon and ham is treated with nitrites and nitrates as part of the preserving process (meat simply treated with salt may be less harmful, but the nitrites preserve the colour of the meat).
Bacteria in the intestine, particularly the colon, convert these to nitroso (NOCs, in the literature).
Haem protein, contained in red meat particularly, can also be converted to nitroso compounds by gut bacteria. The lower amount of haem in white meat is the reason that it is less carcinogenic.
Compounds generated by high heat cooking (the Maillard reaction, which produces the tasty caramelised edges of roasted meat is a prime source)are also sources of nitroso compounds.
An example from the EPIC study of gastric and oesophageal cancer development related to consumption of red and preserved meat.
This study followed the development of 330 cases of gastric cancer and 65 of oesophageal cancer.
The absolute risk of developing gastric cancer over 10 years was found to be 0.26% for people in the lowest quartile of meat consumption, compared to 0.33% in the highest quartile.
The hazard ratio (HR) associated with a 100g/day increase in total meat consumption was 3.52.
The hazard ratio associated with a 50g/day increase in red meat consumption was 1.73 compared with a HR of 2.45 associated with a 50g/day increase in processed meat consumption.
Risks were higher in people with H. pylori infection, HR associated with a 100g/day increase rising to 5.32 .
Q: What is aflatoxin and how is it produced?
Q: How does aflatoxin contaminate food products?
Q: How is aflatoxin metabolized in the body?
A: Aflatoxin is a compound produced by Aspergillus, a type of fungus that can grow on various food crops when stored in warm, moist conditions. Commonly contaminated crops include grains and peanuts.
A: When contaminated crops such as grains and peanuts are milled to produce flour, the product becomes contaminated with aflatoxin.
A: Aflatoxin is metabolized by cytochrome P450 (Cyt P450) enzymes in the liver. During this process, it can become a potential mutagen.
Q: What type of cancer is most commonly associated with aflatoxin exposure?
Q: Can aflatoxin cause other types of cancer?
Q: Why is aflatoxin considered a significant health concern?
A: The most common cancer associated with aflatoxin exposure is liver cancer, due to the formation of the mutagen in the liver.
A: Yes, aflatoxin can be transported to other parts of the body and cause different types of cancer, although liver cancer is the most prevalent.
A: Aflatoxin is considered a significant health concern because it is a common food contaminant that has been long known to be involved in cancer causation. Its ability to act as a mutagen makes it a potent carcinogen.
