Cancer Prevention

1
Cancer Prevention

• The Role of Diet and Nutrition

2
Historical Perspective

• A generation ago, in the 1970s, conventional
  medicine denied any connection between diet and
  cancer. Research data was minimal.
• There has been an upsurge in research on this
  topic since then.
• It is now broadly accepted that nutrition
  strongly influences the development of many
  cancers.

3
Review of Malignancy Process

• Cancer starts when the DNA in a cell is damaged
  by a toxic chemical, radiation, or other factors,
  causing it to multiply.
• Eventually, the growing tumor invades healthy
  tissues and may also release some of its cells to
  travel to other parts of the body where new
  tumors form, a process called metastasis.

4
Ways That Food Influences Malignancy

• Some foods contain chemical carcinogens. Foods
  can also influence cancer risk in other ways
• Foods affect the concentration of sex hormones in
  the blood, which influences the risk of cancer of
  the prostate, breast, uterus, and ovary.
• Some foods increase the formation of carcinogens
  in the digestive tract, while others have the
  opposite effect. This is of particular importance
  in cancers of the colon and rectum.
• Foods can alter the ability of the immune system
  to recognize and eliminate cancer cells.

5
National Cancer Institute(www.cancer.gov)

• National Cancer Institute on modifiable cancer
  risk factors
• Alcohol consumption (associated with increased
  risk of oral, esophageal, breast, and other
  cancers)
• Obesity (associated with colon, breast,
  endometrial, and possibly other cancers).
• NCI these are observational studies, not
  necessarily indicating causation.

6
More from NCI

• Epidemiological studies suggest association
  between high fruit and vegetable consumption and
  reduced risk of various cancers.
• Quality of this evidence has been questioned, and
  it remains uncertain.

7
NCI on Causes of Cancer

• Tobacco 30
• Diet 35-60
• Air/Water Pollution 15
• Alcohol 3
• Radiation 3
• Medications 2
• 1. National Cancer Institute. Cancer rates and
  risks. Washington, DC, 1985.2. Doll R, Peto R.
  The causes of cancer quantitative estimates of
  avoidable risks of cancer in the United States
  today. J Natl Canc Inst 1981661191-308.

8
American Cancer SocietyDietary Recommendations

• Strong scientific evidence that healthful dietary
  patterns, in combination with regular physical
  activity, can reduce cancer risk.
• Approximately 35 percent of cancer deaths in the
  United States may be avoidable through dietary
  modification.
• http//caonline.amcancersoc.org/cgi/content/
• full/52/2/92

9
ACS on Single Nutrients

• Important questions remain unanswered.
• Not yet clear how single nutrients, combinations
  of nutrients, overnutrition and energy imbalance,
  or amount and distribution of body fat at
  particular stages of life affect one's risk of
  specific cancers.

10
ACS on General Direction of Diet

• Epidemiological studies show diets that are high
  in vegetables and fruits and low in animal fat,
  meat, and/or calories have a reduced risk of some
  of the most common types of cancer.
• Until more is known about the specific components
  of diet that influence cancer risk, the best
  advice is to emphasize whole foods and certain
  broad dietary patterns, as described within these
  guidelines.

11
ACS on Vegetables and Fruits

• Presently unclear which components of vegetables
  and fruits are most protective against cancer.
• Vegetables and fruits are complex foods, each
  containing more than 100 potentially beneficial
  vitamins, minerals, fiber, and other substances
  that may help to prevent cancer.

12
ACS on Vegetables and Fruits (2)

• Vegetables and fruits also contain specific
  phytochemicals, such as carotenoids, flavonoids,
  etc., that show benefit against certain cancers
  in experimental studies.
• Implicit in ACS rx too much uncertainty to
  recommend specific supplementation.

13
ACS on Vegetables and Fruits (3)

• Eat a variety of healthful foods, with an
  emphasis on plant sources.
• 5 or more servings of a variety of vegetables and
  fruits each day.
• Include vegetables and fruits at every meal and
  for snacks.
• Limit French fries, snack chips, and other fried
  vegetable products.
• Choose 100 juice if you drink fruit or vegetable
  juices.

14
ACS on Whole Grains

• Choose whole grains in preference to processed
  (refined) grains and sugars.
• Choose whole grain rice, bread, pasta, and
  cereals.
• Limit consumption of refined carbohydrates,
  including pastries, sweetened cereals, soft
  drinks, and sugars.

15
ACS on Meat and Other Proteins

• Limit consumption of red meats, especially those
  high in fat and processed.
• Choose fish, poultry, or beans rather beef, pork,
  and lamb.
• Lean cuts, smaller portions.
• Baking, broiling, or poaching rather than frying
  or charbroiling.

16
ACS on Healthy Weight

• When you eat away from home, choose foods that
  are low in fat, calories, and sugar, and avoid
  large portion sizes.
• Eat smaller portions if you have high-calorie
  foods.

17
ACS on Weight (2)

• Be aware that "low-fat" or "nonfat" does not mean
  "low-calorie," and that low-fat cakes, cookies,
  and similar foods are often high in calories.
• Substitute vegetables, fruits, and other
  low-calorie foods for calorie-dense foods such as
  French fries, cheeseburgers, pizza, ice cream,
  doughnuts, and other sweets.

18
ACS on Alcohol

• People who drink alcohol should limit their
  intake to no more than two drinks per day for men
  and one drink a day for women.
• Recommended limit lower for women because of
  their smaller body size and slower metabolism of
  alcohol.
• A drink of alcohol 12 oz. beer, 5 oz. wine, or
  1.5 oz. of 80-proof distilled spirits.

19
Alcohol and CA (2)

• Alcohol is established cause of cancers of the
  mouth, pharynx, larynx, esophagus, liver, and
  breast. (Possibly for colon.)
• Risk increases substantially with more than two
  drinks per day.
• Alcohol tobacco increases the risk of cancers
  of the mouth, larynx, and esophagus far more than
  the independent effect of either drinking or
  smoking.

20
Alcohol and Breast CA

• Regular consumption of even a few drinks per week
  has been associated with an increased risk of
  breast cancer in women.
• Mechanism uncertain, but may be due to
  alcohol-induced increases in circulating
  estrogens or other hormones in the blood,
  reduction of folic acid levels, or to a direct
  effect of alcohol or its metabolites on breast
  tissue.

21
Alcohol CA vs. CV

• Complication moderate intake of alcoholic
  beverages appears to decrease the risk of
  coronary heart disease in both men and women. But
  a risk factor re cancer.
• ACS women who are at high risk of breast cancer
  might reasonably consider abstaining from
  alcohol.
• Public health officials advise people who already
  drink alcoholic beverages to limit their intake
  to two drinks a day for men and one drink per day
  for women.

22
ACS Rx on Alcohol

• There is no compelling reason for adults who
  currently do not consume alcoholic beverages to
  start consuming alcohol to reduce their risk for
  heart disease, as cardiovascular risk can be
  reduced by not smoking, consuming a low-saturated
  fat diet, avoiding obesity, staying physically
  active on a regular basis, and controlling blood
  pressure.

23
The China Study

• Most comprehensive epidemiological nutrition
  study of all time.
• 1980s in China.
• Collaboration of Cornell, Oxford, and Institute
  of Food Nutrition and Safety of Chinese Center
  for Disease Control and Prevention.
• Campbell, T. Colin. The China Study. Benbella
  Books, 2004

24
China Study (2)

• Gathered data on 367 variables
• Compared each variable with every other variable.
  
• Questionnaires and blood tests to 6500 adults in
  65 Chinese counties.
• Urine samples from all participants
• Directly measured everything that participants
  ate over a 3-day period

25
China Study (3)

• Analyzed food samples from markets all over the
  country
• Mined all available epidemiologic databases to
  correlate their findings with the known incidence
  of diseases in particular locales.
• Found more than 8000 statistically significant
  associations between lifestyle, diet, and disease
  variables.

26
T. Colin Campbell

• Among worlds foremost nutrition researchers
• Major research specialty protein
• Animal and human studies over 30 years, hundreds
  of peer-reviewed articles.

27
Campbell (2)

• Concluded that carcinogens initiate cellular
  changes that may become malignant, but
• Key promoting factor determining whether the
  person develops cancer is quantity of animal (but
  not plant) protein in diet. More animal protein
  more cancer.
• Singled out casein (major protein in milk) as
  single worst offender.

28
Plant and Animal Foods

• In Campbells rat studies at Cornell
• Animal based foods increased tumor development
• Plant based foods decreased tumor development
• China study confirmed these basic conclusions in
  population-based human research

29
Plant and Animal (2)

• Campbell
• The more a person relies on animal foods (all
  types of meat, dairy and eggs), the more likely
  he or she is to develop heart disease, cancer,
  diabetes, osteoporosis, autoimmune diseases, and
  a host of other illnesses of affluence.

30
Major Problem with Nutrition Research in West

• Campbell Before China Study, nutritional
  scientists had to rely almost entirely on Western
  research
• Virtually without exception Western research
  involves people whose diets are either high in
  animal foods or very high in animal foods.

31
Contrast with China in the 1980s

• In sharp contrast, the Chinese subjects generally
  had diets low in animal foods.
• Campbell describes their diets as either high
  in plant foods or very high in plant foods.
• As a result, patterns long considered normal in
  the West (e.g., cholesterol levels, incidence of
  heart disease, stroke, cancer, diabetes,
  osteoarthritis, and osteoporosis) were discovered
  to be quite abnormal in China in 1980s.

32
Addendum to China Study

• Since the 1980s, China has experienced vast
  economic growth (especially in urban areas),
  resulting
• in . . .
• Large dietary increase in Western foods
• Large increase in Western diseases (diseases of
  affluence)

33
Specific Diet-Related Cancers in USA

• Breast
• Uterus and ovary
• Prostate
• Colon

34
Breast Cancer

• Mammography and breast exam are very important
  for early detection, but they do not prevent
  cancer
• Preventing is far better than detecting
• Tumor large enough to be detected has been
  growing for several years
• Diet is key factor in prevention of breast cancer

35
Breast Cancer Cross Cultural Perspective

• Asian countries, such as Japan, have very low
  breast cancer rates compared to Western countries
  where rates are many times higher.
• When Japanese women westernize their diets, as
  has been happening since the 1950s, their breast
  cancer rates climb.

36
Japanese Women and Breast Cancer

• Among affluent Japanese women, those who eat meat
  daily have 6x higher risk of breast cancer
  compared with those who rarely or never eat meat.
• When Japanese families move to the United States,
  their daughters acquire the same risk of cancer
  as the other American women
• Hirayama T. Epidemiology of breast cancer with
  special reference to the role of diet. Prev Med
  19787173-95.Armstrong B, Doll R. Environmental
  factors and cancer incidence and mortality in
  different countries, with special reference to
  dietary practices. Int J Cancer 197515617-31.

37
Fat and Breast Cancer

• The 1988 Surgeon Generals Report on Nutrition
  and Health stated
• . . . a comparison of populations indicates that
  death rates for cancers of the breast, colon, and
  prostate are directly proportional to estimated
  dietary fat intakes.

38
Fats and Estrogen

• High-fat diets increase estrogen levels. which
  encourage the growth of breast cancer cells.
• Reducing the amount of fat in the diet reduces
  estrogen levels quickly (within weeks).

39
Animal Fat vs. Vegetable Oil in BrCA

• NYU researchers compared 250 women w/BrCA to 499
  women w/o cancer from the same province in
  northwestern Italy.
• The groups ate about the same amount of olive oil
  and carbohydrates.

40
NYU Italy Study (2)

• Cancer patients had habitually eaten more meat,
  cheese, butter, and milk.
• Women who consumed more animal products had as
  much as three times the cancer risk of other
  women.
• Toniolo P et al. Calorie-providing nutrients and
  risk of breast cancer. J Natl Cancer Inst
  198981278.

41
2nd Italian Study Yields Opposite Conclusion

• Another observational study in Italy finds
  increased consumption of dairy products to be
  inversely associated with risk of breast cancer,
  particularly among premenopausal women.
• Kesse Guyot E, Bertrais S, et al, Annals of
  Nutrition and Metabolism, 2007 51(2) 139-145.

42
What Might This Mean?

• An outlier, but points to limits of observational
  studies
• Observational dairy studies have often been
  confounded by the fact that health-conscious
  women tend to be the big dairy consumers (i.e.,
  they are doing what they believe to be
  healthful).
• This means they are also engaged in other
  healthful behaviors that influence their risks.

43
Meaning (2)

• Neal Barnard, MD We saw this with dairy and
  body weight. The observational studies suggest
  that dairy consumers are thinner. As soon as you
  test it as a randomized trial, the effect
  disappears. Same as HRT and heart disease.

44
More Fiber, Not JustLess Fat

• As liver filters blood, it removes excess
  estrogens and sends them through the bile duct
  into the intestinal tract.
• There, fiber soaks them up, carrying them out
  with the wastes.

45
Fiber and Estrogens

• Animal products and refined sugars have no fiber.
• To the extent that such foods displace fiber-rich
  foods in the digestive tract, waste estrogens can
  pass back into the bloodstream.
• Whole grains, legumes, vegetables, and fruits
  supply fiber to help insure that waste estrogens
  are eliminated properly.

46
Soy and Breast CancerPrevention

• Soy appears to protect against development of
  BrCA.
• Women who ate soy four times a week or more
  during adolescence and adulthood were nearly 50
  less likely to develop breast cancer than women
  who ate soy less than once a month.
• Carcinogenesis 2002. 23(9)91491-1496

47
Soy and Existing Breast Cancer

• Research is in a preliminary state regarding soy
  effects on existing BrCA.
• Some scientists theorize that it protects by
  docking at estrogen receptor sites and thereby
  blocking actual estrogen from promoting cancer.
• Others theorize that its phytoestrogens act just
  like estrogens and that soy itself promotes
  cancer.
• Bottom line cannot say with certainty.

48
Cancer of Uterus and Ovary

• Like breast, sensitive to hormones and therefore
  to diets high in fat
• Obesity increases risk
• Supplemental estrogen increases risk

49
Galactose in Ovarian Cancer

• Galactose (a milk sugar) can increase risk. Women
  with low levels of enzyme to break it down have
  triple the risk of ovarian cancer.
• Non-fat milk not better. CHO (not fat) is the
  issue here.
• Cramer DW, Willett WC, Bell DA, et al. Galactose
  consumption and metabolism in relation to the
  risk of ovarian cancer. Lancet 1989266-71

50
Prostate Cancer

• Most common cancer for males in US, although lung
  CA kills more men
• Strongly linked to dietary factors in
  epidemiologic studies, particularly animal
  products milk, meat, eggs, cheese, cream,
  butter, and fats.
• But large 2008 European Union study shows no
  correlation with fats.
• Crowe et al. American Journal of Clinical
  Nutrition 2008 87(5)1405-1413
• Countries with a higher consumption of rice, soy,
  or green or yellow vegetables have far fewer
  prostate cancer deaths.

51
Fruits and Vegetables Re Prostate Cancer

• Fatty, fiber-deficient foods tend to increase
  testosterone activity.
• Vegetables and fruits are low in fat and high in
  fiber, resulting in reduced testosterone levels.
• This protects against prostate cancer
• As is common with hormone-related cancers,
  vegetarians have lower prostate cancer rates.

52
Lycopene

• Red pigment that gives watermelons and tomatoes
  their red color. Strong antioxidant.
• Fruits rich in lycopene associated with reduced
  prostate cancer risk.
• Harvard study of 47,000 health professionals
  found that men who had ten or more servings a
  week of lycopene-rich foods had a 45 percent
  reduced risk of prostate cancer.
• Giovannucci E et al. J Natl Cancer Inst
  1995871767-76.

53
Colon Cancer

• There is an association between Western diets and
  colon cancer.
• Meat-eaters have approximately 3x the risk of
  colon cancer compared to those who rarely or
  never eat meat.
• Willett WC et al. Relation of meat, fat, and
  fiber intake to the risk of colon cancer in a
  prospective study among women. N Engl J Med
  19903231664-72.

54
Possible Diet-Colon Cancer Mechanism

• After a fatty meal, the gallbladder releases bile
  acids into the intestine, where they chemically
  modify fats so they can be absorbed.
• Colonic bacteria turn bile acids into
  cancer-promoting secondary bile acids.
• Meat consumption fosters the growth of bacteria
  that encourage the production of secondary bile
  acids.

55
Cooked Meats and Colon Cancer

• As animal proteins are heated, they produce
  heterocyclic amines, known carcinogens.
• National Cancer Institute research well-done
  burger or steak 30 nanograms per gram of the
  carcinogen PhIP
• Grilled chicken 480 nanograms per gram, 15
  times higher than beef.
• Sinha R et al. High concentrations of the
  carcinogen 2-amino-1-methyl-6-phenylimidazo-4,5p
  yridine (PhlP) occur in chicken but are dependent
  on the cooking method. Cancer Research
  1995554516-9.

56
Marinating Meat Decreases HCA Formation

• Research at Kansas State University, 2008. Click
  here.
• Marinades tested were rich in spices from mint
  family

57
Foods That Protect Against Colon Cancer

• Fruits and vegetables, as noted earlier
• Fiber reduces production of carcinogenic
  secondary bile acids and also absorbs and dilutes
  bile acids.
• Cruciferous vegetables are protective against
  colon and other cancers.
• Broccoli, cabbage, kale, collard greens,
  cauliflower, Brussels sprouts

58
Antioxidants

• Free radicals -- unstable oxygen species produced
  in the course of cellular metabolism.
• Damage to DNA -- believed to be initiating step
  in cancer.
• Aside from being low in fat and high in fiber,
  fruits and vegetables also rich in antioxidants
  that neutralize free radicals.

59
Key Antioxidants

• Vitamin C -- in many fruits and vegetables,
  particularly citrus fruits
• Beta-carotene -- orange, yellow, and green
  vegetables
• Vitamin E -- grains and beans
• Selenium -- many grains, vegetables, fruits, and
  legumes

60
Antioxidants in Foods vs. Supplements

• A diet emphasizing foods high in antioxidants is
  protective against cancer.
• There is not at this time convincing evidence
  that antioxidant isolates in supplements are
  protective.
• The supplement question is unresolved.