6 Nutrition and Cancer

Question 1

List some dietary factors involved in the development and prevention of cancer

Answer 1

• Obesity
• Red and processed meat
• Saturated fat
• Alcohol
• Fruit and Vegetables
• Fibre
• Dairy and Calcium

Question 2

Why is obesity commonly linked to cancer? (reason)

Answer 2

Due to chronic low-level inflammation

Question 3

List some cancers commonly associated with obesity

Answer 3

• Colorectal, prostate, liver, kidney, multiple myeloma, meningioma, pancreatic, oesophageal, gastric, cardiac, gall bladder, endometrial, breast (m + f)

Question 4

Describe the mechanism(s) by which obesity is linked to cancer

Answer 4

• Adipose tissue leads to increased levels of estrogen, which is associated with the risk of certain cancers
• Changes in circulation of certain adipokines -
  > increased leptin (promotes cell proliferation)
  > decreased level of adiponectin (antiproliferative effects)
• Increased circulating insulin - insulin signaling through insulin receptor A; has direct oncogenic effects on cancer cells
• Increased insulin-like growth factor (IGF) 1 -
  > it is a survival agent and growth factor for a diverse range of normal and malignant cells

Question 5

List some cancers associated with intake of red and processed meats

Answer 5

Increased risk of colorectal and GI cancers

Question 6

Describe the roles nitrosamines play in cured meats and cancer risk

Answer 6

Nitrosamines (potent carcinogens) are formed in cured meats because nitrite, and sometimes nitrate, are added to these meats during processing
- Upon consumption, nitrates can be converted into N-nitroso compounds (NOCs), which are carcinogenic

Question 7

Describe how red meats are shown to promote colorectal tumorigenesis

Answer 7

Haem iron (present at high levels in red meats) has been shown to promote colorectal tumorigenesis by stimulating the endogenous formation of carcinogenic N-nitroso compounds

Question 8

Describe why the cooking of processed meats is linked to colorectal cancer development

Answer 8

Processed meats are often cooked at high temperatures, which can lead to the formation of:

• heterocyclic amines (HCAs)
• polycyclic aromatic hydrocarbons (PAHs)

both of which have been linked to colorectal cancer development

Question 9

List some cancers which are associated with saturated fats

Answer 9

Increased risk of lung, colorectal, prostate, and breast cancer

Question 10

List some mechanisms by which fats promote tumourigenesis

Answer 10

• High fat intake results in increased production of bile acid, which is converted by intestinal bacteria into secondary bile and cytotoxic compounds:
  > these compounds may enhance the proliferative activity of the colonic epithelium
• High-fat diets are often associated with obesity
  > high-fat-induced obesity can lead to a chronic state of low-grade inflammation
• High dietary SFA intake is often synonymous with a high intake of processed and red meat
• Dietary intake of certain types of fat (Omega 3 PUFAs) is inversely correlated with the development of certain cancers
• With high-fat diets, insulin levels rise too (resulting in oncogenic effects on cancer cells)

Question 11

List some cancers associated with alcohol

Answer 11

Alcohol has been identified as a contributory factor for several types of cancer including upper aerodigestive tract, liver, and breast

Question 12

Explain the role of acetaldehyde in alcohol-related cancer risk increase

Answer 12

Acetaldehyde is the first metabolite of ethanol oxidation.

- Acetaldehyde has been shown to be mutagenic and carcinogenic in animal experiments

Question 13

Explain the role of oestrogen in alcohol-related cancer risk

Answer 13

• Alcohol can increase the circulating levels of estrogen, which is linked to breast cancer

Question 14

Explain the role of folate and other nutrients in alcohol-related cancer risk

Answer 14

• Epidemiological studies have indicated a negative association between folate intake and risk of breast cancer
• As well as a negative association between Vitamin B12 status and risk of breast cancer postulated that the lower folate and B12 levels in individuals consuming alcohol can increase cancer risk

Question 15

Explain the role of alcohol and smoking in cancer-related risk

Answer 15

Alcohol and smoking have a synergistic effect

- High alcohol consumption can also cause cirrhosis of the liver, which can then lead to cancer

Question 16

Explain the mechanisms behind the association between regular consumption of fruits + vegetables and reduced risk of cancer

Answer 16

• Antioxidants interact with and neutralize free radicals (aka ROS - reactive oxygen species)
• Glucosinolates and isothiocyanates - increase elimination/
  metabolism of carcinogens (nitrosamines)

Question 17

Explain the mechanism behind how dietary fibre is thought to protect against colorectal cancer

Answer 17

• Formation of short-chain fatty acids from fermentation by colonic bacteria
  > these SCFAs (e.g. Butyrate) can inhibit the development of colorectal cancer
• Reduction in intestinal transit time

Question 18

List some cancers which are believed to have a lower risk if there is the consumption of dairy and calcium

Answer 18

• Bowel cancer, bladder cancer, prostate cancer

Question 19

Describe the mechanism of how dairy and calcium is linked to lower risk of some cancers

Answer 19

• Some studies have shown the presence of sphingolipids, calcium, conjugated linoleic acid, butyric acid, and lactic acid bacteria in dairy products; which have the potential to reduce bowel cancer
• Ionised calcium or calcium phosphate may reduce colon cancer by binding to secondary bile acids and free fatty acids to form insoluble soaps, which can have a protective effect on the epithelial cells of the colon

Question 20

List some advice on diet and lifestyle that can be given to patients

Answer 20

• Maintenance of normal body weight
• Increase intake of fruit and vegetables
• Increase intake of plant foods rich in complex carbohydrates/fiber
• Limit intake of red meat, animal fats (+ processed meats)
• Limit alcohol consumption

Question 21

Describe some advice that can be given on maintenance of a normal body weight

Answer 21

• Physical activity according to guidelines (150min of moderate activity per week)
• Advice on energy balance, referrals to specialists/schemes when appropriate
• Important to understand that obesity is a very complex condition

Question 22

Describe some advice that can be given on increasing intake of fruit and vegetables

Answer 22

• In UK, it is currently recommended that individuals consume a minimum of 5 portions of fruit and vegetables a day
• BUT more is better – a major review found people who regularly ate 800g of fruit + veg a day (10 portions) had a significantly lower risk of chronic diseases
  o All fruit + veg (not potatoes), pulses, tinned fruit (low sugar), dried fruit (not too much – high sugar content)

Question 23

Describe some advice that can be given on increasing intake of plant foods rich in complex carbohydrates/fibre

Answer 23

Fibre-rich foods include:

• Wholegrain breakfast cereals, wholewheat pasta, wholegrain bread and oats, barley and rye
• Fruits such as berries, pears, melon, and oranges
• Vegetables such as broccoli, carrots, and sweetcorn
• Peans, beans, and pulses
• Nuts and seeds
• Potatoes with skin

Question 24

Describe some advice that can be given on limiting the intake of red meat, animal fats (+ processed foods)

Answer 24

The current advice says:

• Adults who eat more than 90g of red and processed meat a day should reduce their intake to 70g a fay
• Eat no more than 500g of red meat a week, and avoid processed food

Question 25

Describe some advice that can be given to limit the consumption of alcohol

Answer 25

• To keep health risks from alcohol to a low level, it is safest not to drink more than 14 units a week on a regular basis
• If you regularly drink as much as 14 units per week, it’s best to spread your drinking evenly over 3 or more days. If you have one or two heavy drinking episodes a week, you increase your risk of long-term illness and injury
• Risk of developing a range of health problems (including cancers of the mouth, throat, and breast) increases the more you drink on a regular basis
• If you wish to cut down the amount you drink a good way to help achieve this is to have several drink-free days a week