Physical Activity and Cancer Risk Reduction - Mechanisms Flashcards
What are the three ways PA and cancer risk reduction is related?
- Indirect association between physical activity and cancer
- The direct effect of physical activity itself on cancer
- The effect of obesity on cancer
What is the indirect association b/w cancer and PA?
Correlation between two variables due to the presence of a common third variable - the confound
- each variable is closely related to this confound
Example of a confound
Although PA reduces risk of cancer, so do other lifestyle factors like diet and smoking
What is an effect of pre-existing disease?
Causes a person to reduce PA
How does fibre reduce the risk of cancer?
- Binds carinogens
- Altering gastrointestinal flora
- Increasing speed of transit
How is physical activity related to dietary fibre?
- Active people tend to eat more fibre
- PA reduces cancer risk when it’s the confound of a fibre filled diet
What do antioxidants do?
“clean up” free radicals
How is physical activity related to antioxidants?
- Active people tend to eat more antioxidants
- PA reduces risk of cancer when it’s the confound of antioxidants in the diet
How are vitamins related to PA and cancer risk?
- Active people are more likely to take Vitamin D and other supplements
- Some studies show large doses of vitamins may decrease cancer risk
How is socioeconomic status related to physical activity and cancer risk?
Active people tend to be
- Wealthier
- Live in less polluted areas
- Less likely exposed to occupational carcinogens
All the factors above can reduce cancer risks
How are sex hormones a direct affect on cancer risk?
They increase cell proliferation and decrease cell apoptosis
What is Plasma Testosterone?
It’s associated with risk of some hormones sensitive cancers in men
What is Plasma Estrogen?
Associated with risk of some hormone sensitive cancers in women
What level of sex hormones in the blood reduces cancer risk?
Reduced/low sex hormone levels in the blood
What in relation to the menstrual cycle increases breast cancer risk?
More menstrual cycles in a lifetime means a greater risk of developing breast cancer
What is protective in women against risk of cancer development? (x3)
- Late menarche (starting periods later in life 12-13 years)
- Early menopause
- Pregnancy
Less estrogen exposure to breast tissue the better
How can heavy exercise in girls be helpful in reducing breast cancer risk?
Heavy exercise delays menarche and reduces the total number of cycles in a lifetime
How is Physical activity and Estrogen related to reducing cancer risk in Premenopausal adult women?
Physical activity is associated with decreased levels of circulating estrogen and progesterone
How is Physical activity and Estrogen related to reducing cancer risk in Postmenopausal adult women?
Physical activity is associated with decreased serum estrogen and androgens
What are androgens?
Male sex hormones associated with increasing cancer risk
What cancer risk is increased when taking anabolic steroids?
Liver cancer risk increases
How might Physical Activity related to Androgens to reduce prostate cancer risks? Is this conclusive?
Physical activity may reduce cancer risk by reducing circulation of androgens
Inconclusive at this time
How are Insulin and Insulin like Growth Factor (IGF) related to cancer?
These are promoters for breast and colon cancer cells because they increase sex hormones and cell proliferation
What can control Insulin and IGF?
Physical activity strongly controls them by counteracting the increase in sex hormones and cell proliferation
What does elevated cortisol levels do to the body when stressed or nervous?
Depress immune system causing issues with functioning to fight off cancer cells
How is Physical activity and cortisol related to reducing cancer risk?
Regular physical activity decreasing resting cortisol levels ensuring immune system is functioning properly
When are Prostaglandins released?
Released from exercise-induced microtrauma
What do Prostaglandins do?
May increase movement of the GI tract that reduces risk of colon cancer
Can also reduce cell proliferation
What is the 2-stage of Tumour formation?
- Normal cell gives rise to a precancerous cell
- Further changes produce a cancerous cell that is capable of rapid replication
Why is the immune system important in Tumour formation?
Counters the 2-stage formation by finding precancerous cells and cancerous cells and gets rid of them
What stimulates the immune system?
Physical activity
What can depress the immune system function?
Overtraining
What parts of the immune system attack cancer cells?
- Macrophages
- Natural Killer cells (NK cells)
- Lymphocytes
- Neutrophils
- Lymphokine-activated killer cells (LAK cells)
What do macrophages do?
Play a dominant role in cancer prevention by eating cancer cells and stimulates other parts of the immune system
What can initiate macrophage activity when low?
- Inflammatory signals
- Microtrauma from physical activity
What do Natural Killer Cells do?
Play a surveillance role and attack most types of cancer cells
What increases natural killer cells?
Vigorous physical activity
Who has higher natural killer cell count?
Regular exercisers
What do Cytolytic T lymphocytes do?
Kill tumour cells
What enhances activity of cytolytic T lymphocytes?
Regular moderate Physical activity
What are Interferons? (IFN-a)
- Inhibits growth and division of tumour cells
- Activates macrophages and natural killer cells to get rid of cancer cells
What increases INF-a?
Physical activity
What are Tumour Necrosis Factors? (TNFs)
Damages tumour cells
What increases levels of TNFs?
Increased levels after endurance physical activity
