Unit 7: Diet and Cancer

cancer is less common in Canada today than it was 50 years ago. Select one: a. Stomach b. Breast c. Prostate d. Lung

(a) Stomach cancer is less common in Canada today than it was 50 years ago. The correct answer is: Stomach

Dietary factors are linked to of all cancer cases

1/3

What is the recommended supplement intake of vitamin D?

1000 IU daily

What does carcinogenesis interfere with?

Growth restraint, prevent cellular death, promote cellular growth

What does carcinogenesis arise from?

Mutation of genes that control cell division in a single cell

What is the relationship between dietary fat and breast cancer

Populations with higher fat intake tend to have high rate of breast cancer (and low intake of cereals)

what is the effect of refrigeration on food preservation that may affect the risk of stomach cancer?

Refrigeration reduces nitrate need for food preservation

A researcher carries out a case-control study in which the past diet of patients with pancreatic cancer is compared with that of matched controls. The cancer patients are found to have a lower intake of vitamin C. How would you interpret this observation?

This observation could indicate that vitamin C is protective. However, it could also mean that other substances in food associated with vitamin C are the true protective factor(s). There are also other possibilities. For instance, the results might be biased because of error in diet assessment (e.g., people with cancer may under-report their vitamin C intake).

Benign tumor

abnormal mass of cells that is not cancerous

Why is it difficult to prove the link between beta-carotene and cancer

confounding animal studies effects but RCT in 1990s showed negative results

Lycopene appears to reduce the risk of what cancer?

prostate

Why is it difficult to determine if a specific vitamin or mineral is protective against cancer?

-hard to obtain accurate information on intake -micronutrients often correlated with each other in diet -many other substances found in foods could have an effect on outcome

What is a tumour?

Abnormal tissue mass with no physiological function and can disrupt functioning of normal tissue around it

What evidence shows that salt intake is related to stomach cancer?

Animal studies - rats given carcinogen that induces stomach cancer and given high salt intake have accelerated disease development cohort studies population studies - japan had the world's high rates for both stomach cancer and stroke; diet is traditionally high in salt - salt intake associated with hypertension and stroke

Discuss the health benefits of high fibre diets and the types of fibre for preventing CDL.

Bacterial fermentation of fibre produces short-chain fatty acids. One of these acids, butyrate (C4), may be directly anti-carcinogenic. Fatty acids lower pH in the colon, which helps prevent conversion of primary secondary bile acids, such as deoxycholate, which is thought to be carcinogenic. Fibre binds to bile acids and other possible carcinogens and prevents them from attacking the colon. Soluble fibre is the most effective at lowering blood cholesterol High fibre foods, especially whole grains - reduce type 2 diabetes. Soluble fibres trap nutrients and delay transit through the GI, slowing glucose absorption

Which nutrient has the strongest negative associate with lung cancer?

Beta-carotene. RR about 0.5 May explain why not all smokers get lung cancer

What are the strengths and weakness of cross sectional studies?

Can reveal associations between variables healthy controls are usually less keen. There is also a tendency for people with healthy lifestyles to volunteer.

What evidence is there for the effect of fruits, vegetables in the prevention of cancers?

Case control studies - person who eats extra 100grams per day decreases risk by about 10% Cohort studies - generally more free from bias than case control and show weaker degree of protection

What are some ways of cooking meat that may accelerate tumor development?

Cooking meats at high temperatures, eg. frying and broiling and grilling

What is the effect of dietary fibre on colon cancer?

Diet high in fibre-rich foods is likely to prevent colon cancer

What is selenium?

Essential trace mineral that acts as an antioxidant in the body

What is the evidence for vitamin E as an anti carcinogenic?

Evidence is weaker than for other nutrients

Beta-carotene has been proven to be anti-carcinogenic. True or False? Support your answer with a brief explanation.

False. See the subsection titled "Beta-carotene" in Section 3. The correct answer is: False

How does estrogen affect breast cancer?

Implicated in breast cancer for postmenopausal women. Fat tissue produces estrogen so obese postmenopausal women have higher estrogen levels

What are the two main stages of carcinogenesis?

Initiation and promotion

Comparisons of different countries indicate that prostate cancer is more common where the diet is low in cereals. Does this mean that cereals prevent prostate cancer?

No. An eating style or some other aspect of lifestyle associated with cereals may be responsible for the observations. Alternatively, cereals may be negatively associated with the true cause.

Of the foods listed below, is probably least likely to help prevent colon cancer. Select one: a. oats b. cabbage c. beef d. carrots

Of the foods listed, (c) beef is probably least likely to help prevent colon cancer. The correct answer is: beef

Of the substances listed below, is least likely to help prevent cancer. Select one: a. nitrite b. ascorbic acid c. carotenes extracted from tomatoes d. selenium

Of the substances listed, (a) nitrite is least likely to help prevent cancer. The correct answer is: nitrite

What evidence supports the hypothesis that eating a high fibre diet lowers the incidence of CDL?

Population comparisons - suggest that fibre is protective but cannot determine causality Observations - high fibre diets speed transit time through colon and result in large volume of feces - short transit time allows less time for bacteria in feces to produce carcinogens and less time for carcinogens to be in contact with colon - greater volume of feces dilutes carcinogens

What evidence do we have that red meats and processed meats is positively correlated with colon cancer?

Population studies - strong association between intake of dietary fat and colon cancer Animals studies - rats fed carcinogen that induces colon cancer much more likely to get disease if fed high fat diet

What are environmental factors of carcinogens?

Radiation and sun, water and air pollution, smoking

Why is selenium not recommended as a supplement even though an inverse relationship exists between intake of selenium and several types of cancer?

Selenium is toxic at high doses. TUI is 400 micrograms/day

What are some effects that fibre has on colon which might help prevent colon cancer?

Short chain fatty acids produced by fermentation of bacteria is thought to have anti carcinogenic effects -especially butyrate (C4) -fatty acids lower pH in colon which help prevent conversion of primary to secondary bile acids -binds to bile acids and other carcinogens and prevents them from attacking colon

The evidence for a causal role for dietary meat is strongest in Select one: a. breast cancer. b. lung cancer. c. prostate cancer. d. colon cancer.

The evidence for a causal role for dietary meat is strongest in (d) colon cancer. The correct answer is: colon cancer.

What is carcinogenesis?

The process of cancer development. Proceeds slowly and continues for several decades

True or false. White meat appears to reduce risk of death from cancer?

True

True or false. Overconsumption could be one reason why a Western lifestyle causes Western cancers

True.

What vitamin probably has a protective role in stomach cancer?

Vitamin C

Briefly describe three methods used in the study of the role of dietary fat in the causation of breast cancer.

You may have identified any three of the possibilities listed below. case-control study cohort study population comparisons randomized controlled studies animal experimentation

Tumor

abnormal cells grows network of blood vessels supply tumor and nutrients it needs for support growth. Disrupt functioning of normal tissues around it metasize to other regions of the body

What are the strengths and weakness of historical studies?

advantage of being based on large populations, and they often involve large or even massive changes in disease incidence. disease statistics collected 70 or more years ago can often be unreliable. A more important disadvantage is that confounding Suffers from similar weaknesses as population studies Accordingly, historical evidence does not lead to clear conclusions on its own; however, it is a useful supplement to other types of study

What evidence supports the hypothesis that overconsumption could be one reason why a Western lifestyle causes Western cancers?

animal studies human studies show clear association for breast, endometrium, and colon - consuming excess increases risk but burning up calories has opposite effect

Leukemia

cancer affecting WCB do not form a tumor accumulate in blood tissues and other tissues

What is acrylamide?

carcinogen that is produced when certain starches such as potatoes are fried or baked at high temperatures

What are nitrosamines?

carcinogens formed in stomach from nitrates and nitrites present in food

Cancer development

development: carcinogenesis : slowly and continues several decades. arises from mutations genes that control cell division. Promote cell growth interfere with growth restraint and prevent cellular death. Loses built in capacity for halting cell division and produces daughter cells with same genetic defects

What are carcinogenic initiators?

factors that cause mutations to give rise to cancer, such as radiation or carcinogens. React with DNA in body tissues and cause a chemical alteration in DNA. They are complete carcinogens - can give rise to tumor even without a promotor

What are carcinogenic promotors?

factors the favor the development of cancers once they have begun. Converts initiated cell in to a tumor. requires an initiator

What are the benefits of case controlled studies over cohort studies?

far fewer subjects are needed (hundreds rather than tens of thousands). This greatly reduces the cost. Second, the results are generated far more quickly as there is no need to wait years for diseases to develop.

What is cancer?

growth of malignant tissue (a cancerous cell or tumour) which can injure healthy tissues and spread to other regions

Cancer

growth of malignant tissue. above CVD cause of death in Canada. Not a single disorder. Different characteristics, different locatons and different courses and treatment

What types of cancer is alcohol associated with?

head and neck cancers (mouth, throat, breast ) often damages liver an dprecedes development of liver cancer

What evidence do animal studies show us regarding colon cancer and fibre?

high fibre diet generally protective against colon cancer in rats and mice only thing animal studies clearly indicate is fibre is protective against colon cancer

What are the strengths and sources of error in cohort studies?

information is collected before the disease develops, removing a major source of bias, namely that the participant may have started eating the food in question after or because of the disease outcome. -greatest challenge in analyzing data from cohort studies is confounding -people are notoriously inaccurate in describing their diet. -diet and other aspects of lifestyle, such as smoking and exercise, tend to change over time

What cancer does Vitamin D seem to lower and by what percent?

lowers rates of colon cancer by about 25%

What types of cancers do eating fruits and vegetables seem to help prevent?

lung, mouth, throat, and esophagus, prostate

Vitamin C has been shown to inhibit the chemical reaction of

nitrosamines

Reasons cancer develops

numerous and varied. Vulnerability: inherited genetic defects alters DNA structure functions or repairs. Metabolic processes phagocytes of immune system produces oxidants that cause DNA damage chronic inflammation enhances the rate of the cell division and risk of damaging mutation

What are the strengths and weakness of population studies?

observations in population studies are based on large numbers of cases. Chance, therefore, is an unlikely factor. that disease statistics are often unreliable in non- industrialized countries. Food consumption data can also be misleading. difficult to identify exactly which factor is causally related to the disease under study.

What evidence do we have that dietary fat is positively correlated with breast cancer?

pooling of case control and cohort studies concluded that women at the top 2-% fat intake have 10-20% greater risk of breast cancer than those in the lower 20% population studies showed that populations wwith diet high in fat intake had strong positive correlation with mortality from breast cancer > 0.8 animal studies - high fat diet fed to rats and mice given carcinogen to induce mammary cancer more likely to develop disease

What are the problems with case-controlled studies?

recall bias. This refers to the tendency of patients who have recently been diagnosed with cancer to have a distorted recollection of their past diet, usually in the direction of overstating its unhealthy features. healthy controls are usually less keen volunteer. There is also a tendency for people with healthy lifestyles to volunteer.

What are some recommended ways of cooking meats to minimize carcinogen formation?

roast or bake, taking care not to burn foods, marinating meats beforehand, when grilling, line grill with foil or wrap food in foil