Grab Some Cabbage and Cantaloupe After You Go Jogging

Lera S. Wenger

David Schlundt, Ph.D.

Health Psychology 115A

November 11, 1997

                            Breast Cancer Prevention

 
    Every year for the last fifty years the number of cases of breast cancer in women has steadily increased.  The only cancer that claims more women's lives in the United States is Lung Cancer.
(http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/rates42.html)   This naturally causes concern among women, and thus the question of prevention is immediately asked.  With prevention of lung cancer, the easiest and most effective way is to avoid smoking completely.  Breast cancer, on the other hand does not have such a direct behavioral action that dramatically changes a person's risk.  There are many factors that cause a person to be more at risk for breast cancer, and there is not one simple action of prevention that is as established as not smoking is for lung cancer.
 

Risk Factors for Breast Cancer

     There are numerous risk factors associated with breast cancer.  If a person has family members with breast cancer, especially a mother or a sister, it greatly increases a woman's odds of being diagnosed.   Additionally, women who have their first child before the age of twenty years old are less likely to have breast cancer than women who were over thirty years old at the time of their first child's birth or had no children at all.  If a woman breast fed her babies, her risk goes down as well. The chances become higher for a woman the earlier she began menstruating during adolescence. (http://oncolink.upenn.edu/cancer_news/1994/excersise_bc.html)   Women of higher economic status, living in a more urban environment in the northern United States, and who are married have the highest rates of breast cancer.  (http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/risks120.html)
 
      Clearly, many factors contribute to an individual's chance of having breast cancer; this report concentrates on behavioral associated risk factors such as diet and exercise. Statistics show how countries around the world have rather different rates of breast cancer.  From 1986 to 1988 the death rates of breast cancer victims were compiled.  England and Wales had the highest rate with 29.3 deaths per 100,000 women with breast cancer.   Other European countries tended to have the highest rates, and Asian countries had the lowest.  Thailand had the lowest number of deaths with only one death per 100,000 women from 1986 to 1988.  The United States ranked sixteenth of the fifty countries in the survey with a rate of 22.4 deaths per 100,000 women. (http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/rates42.html)
 
    Incidence rates are roughly five times higher in northern Europe and North America than in Asia. (International Agency for Research on Cancer, 1992)    It has been shown that when women move from a country with a typically low rate of breast cancer to one with a higher rate, the woman's risk gradually increases to that of a typical woman in the country with the higher rate.  Thus, environmental and behavioral differences between the countries must play an important role in an individual woman's breast cancer risk.
 

Dietary Fat

    One theory of the large variance among the country's incidences of breast cancer deals with the amount of fat the people in each country consumes.  As body weight and mass increase in a post menopausal woman, so does her risk of breast cancer.   (http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/risks120.html)    A person's external influences are most likely involved in causing genetic mutations, that in turn cause cancer of the breast.  Behaviors of the person may stimulate the cancer growth initially, and that is why diet can be very influential in determining the risk of breast cancer.   It is thought that the diet of an adolescent woman can be especially important, because that is when breast cells are growing the most.
 
    "Your food shall be your remedy," was written by Hippocrates and still is valid considering that  20 - 60 percent of all cancer deaths were influenced by the diet of the patient.  A diet low in fat intake reduces a person's general cancer risk.  Breast cancer deaths increase when tumors spread.  This happens when tumors spread to nearby tissue, which is invasion.   Breast Cancer also spreads when a tumor grows in a location in the body distant from the breast, and that is called metastasis.  Dr. Rose from the University of Pennsylvania has shown that metastasis has increased in laboratory rats that have human breast cancer cells in their mammary tissue.  This increase was directly correlated with the amount of omega-6 unsaturated fatty acids the rats ingested.  (http://oncolink.upenn.edu/cancer_news/1994/diet_cancer.html)

 

Dietary Fat and its Connection with Ovarian Hormones

    A large multicentre randomized controlled trial found that a low-fat, high-carbohydrate diet reduces the breasts' exposure to ovarian hormones, which in turn helps to prevent breast cancer.  (Boyd 1997)  This long term study involved women that had 50% or greater breast density of the breast area.  All of the women were pre-menopausal.  The participants were between 30 and 65 years old.  The mean age for the enrolled subjects was 42-43 years old.  There were 112 people in the intervention group, and there were 104 control subjects.  The subjects had similar heights and weights.  Additionally 24% of the intervention group and 14% of the control group had at least one first-degree relative that had cancer of the breast.  The women were involved in a randomized trial of dietary intervention.  Its goal was to reduce dietary fat to 15% of the the total calories consumed for the intervention subjects.  The participants were given general advice but were not counseled about their intake of fat.

    After two years of the conducting the study, the intervention and control groups had very similar nutrient intakes records.  There were evident differences between the two groups in other areas of concern.  The mean percentage of energy that came from fat for the intervention group fell from 34% to 21%.  The control group's mean percentage of energy derived from fat remained the same, because they did not reduce their intake of saturated, monounsaturated and polyunsaturated fat.  The subjects in the intervention, on the other hand, did reduce their consumption of those fats, and thus they had the drop in fat energy percentages.   The intervention group had a difference  of 12% in their intake of carbohydrates as well.  Their total carbohydrate consumption rose from 48% to 60%.    The intervention group also ate more fiber over the two year period.  Their level of fiber intake went from 16 to 19 grams a day.  These dietary changes that the intervention group developed were a significant difference from those of the control group.   The members of the intervention group had no change in body weight over the two year period, where as the control group gained about 1.3 kilograms on average.  (Boyd 1997)
 
    The goal of this study was to see if dietary changes such as lowering fat intake, and increasing carbohydrates and fiber would cause a difference in levels of plasma sex hormones.  The proposed theory was that lower levels of ovarian hormones would help reduce the risk of breast cancer.  The amount of the ovarian hormones, oestradiol and progesterone,  in the blood greatly changed over the two year duration of the study.   Blood was drawn from the subjects initially and every year for the next two years.  The intervention subjects had an average reduction of oestradiol of 13.9%, where as the control group had a 2.9% increase of the hormone.  The level of oestradiol of the intervention group was 20.3% lower than the control group after two years.  The change in oestradiol levels was present in the women's blood whether it was before or after their menstrual cycle.  There was an even more drastic change in levels of progesterone between between the two groups of women.  The members in the intervention group had progesterone levels that were 33% lower than the levels corresponding with the subjects in the control group. (Boyd 1997)
 
    The results from this randomized controlled trial indicate that a low-fat, high-fiber, and high-carbohydrate diet reduces ovarian hormones in women.  Such plasma sex hormones are a stimulus to cell division in the breast.  Therefore by reducing the amount of such hormones in women, the amount of exposure that their breasts receive from ovarian hormones is also reduced.  Additionally, the reason that women have a 100-fold excess of breast cancer over men is due to the amount of female sexual hormones in them.  Naturally women have greater amounts of ovarian hormones, thus putting them at a much higher risk for breast cancer.  A woman's chances of developing breast cancer is decreased when her ovaries are removed.  This also relates to how women who start menstruating earlier and go through menopause later are at a higher risk for breast cancer, because they are exposed to ovarian hormones over a longer period of time. (Boyd 1997)
 
    Moreover, populations where women tend to have lower blood levels of ovarian hormones also have fewer cases of breast cancer per capita.  The amount of oestradiol in post-menopausal women in American whites is on average three times higher than levels of recent Asian migrants to Hawaii.  Incidence rates of breast cancer are much lower in Asia then in the United States.  Populations with lower ovarian hormone levels and lower levels of fat in their diet tend to have lower incidence rates of breast cancer.  Reducing dietary fat reduces plasma sex hormones in women, and that in turn reduces a woman's chance of developing breast cancer.  (Boyd 1997)
 
 

Antioxidants, Fruits,Vegetables, Fiber, and Fish and Olive Oils

    Women on low fat diets also have breasts that are less dense.  Lower breast density decreases the risk of breast cancer.  At  U.C.L.A.  Dr. Glaspy is conducting a study exploring what a low fat diet along with soy and fish oil supplements would do to the composition of the breast.  The breast cells taken from the women in the midst of the study had encouraging results.  They had less Omega 6 oils which increase metastasis, the spreading of breast cancer.  The women's breast cell samples also contained more Omega 3 oils which help to keep the breast healthy by protecting it. (http://www.cnn.com/HEALTH/9704/02/breast.cancer/index.html)  Also, many countries with the lowest rates of breast cancer tend to have fish for their main source of  protein.  Studies are currently beginning to study if fish oil and vitamin E could reduce the incidence of breast cancer.  (http://www.cancer.org/bcn/report.html)

     In addition to eating a low fat diet, eating at least five fruits and vegetables a day may reduce your risk of cancer.  There is evidence that the cancer rates for various countries are inversely proportional to the amount of fruits and vegetables eaten by the populations there.  Thus, the more fruits and vegetables consumed, the fewer cases of cancer. (http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/risks73.html)   Fruits and vegetable have many beneficial aspects about them.  They have vitamin A and C, carotenoids, minerals, biochemical compounds, and fiber.   Each of these elements of fruits and vegetables ,in addition to other biochemicals and nutrients in them , help to contribute to a person's overall health as well as fight away cancer.
 
    Studies reveal that nutrition may effect breast cancer incidence.  (Kimmack 1997)  Antioxidants, including vitamins A and C, selenium, carotenoids, zinc, copper, iron, and manganese, may protect breast tissue from the development of cancer.  These micro nutrients do so by protecting the tissue from oxidant damage.  Such substances are the body's ammunition against cellular oxidative damage due to toxic oxygen products.  Free radicals and reactive oxygen molecules are generated endogenously as a result of metabolic reactions.   They bind cellular components and react with unsaturated bonds of membrane lipids, denature proteins, and attack nucleic acids.  Such chemical reactions directly influence cell and tissue damage.  Additionally, they are connected with age-related disorders and are thought to cause cancer.  Vitamins C and E, and carotenoids trap damage causing free radicals.  Selenium, zinc, copper, manganese, and iron are critical components of antioxidants.  Antioxidants may prevent cancer by reducing and suppressing cellular damage caused by oxidants. (Kimmack 1997)  An additional reason to eat fruits and vegetables.
 
    A recent study found that an increase in consumption of fruits, vegetables, and olive oil was associated with a lower breast cancer risk, whereas an increase in margarine increased the risk.  (http://oncolink.upenn.edu/cancer_news/1995/olive_oil.html)    Cruciferous vegetables (broccoli, cauliflower, brussels sprouts & cabbage) have caught quite a bit of attention from researchers.  Rodents who eat a diet with dried cabbage have shown to have a reduced risk of breast cancer.  The positive outcome no longer occurred though when the rats were eating a high fat diet along with the cabbage.  One added benefit of eating many fruits and vegetables is that people who do so generally eat less fat and fewer calories overall.  (http://oncolink.upenn.edu/cancer_news/1994/diet_cancer.html)   Fiber also plays an important role, and studies have revealed that there is a reduction in the risk of breast cancer in women who consume  high fiber diets.  (http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/risks73.html)

    The connection among dietary fiber, vitamins A, C, and E, and breast cancer risk was studied in the Canadian National Breast Cancer Screening Study.  (Kimmack 1997)  In 1982,  56,837 women participated in a self administered diet history.  Risk factors included vitamin supplements and nutrient intake.  From the 56,837,  519 developed breast cancer within the next six years.  The diets of all of the subjects were studied, and the amount of vitamin E intake had a small but positive association with the incidence of breast cancer.  Additionally, there was a stronger relationship with consumption of  dietary fiber, pastas, cereals, and vegetables rich in vitamins A and C  with breast cancer risk.  The more such foods were consumed, the lower the breast cancer incidence.
 

Alcohol

    Alcohol has also shown to have an influence on breast cancer risk.  If a woman drinks two drinks daily throughout her lifetime, then her breast cancer risk may increase 40 to 70 percent.    (http://rex.nci.nih.gov/NCI_Pub_Interface/raterisk/risks120.html)
There is a connection between the amount of alcohol a woman drinks and her risk for breast cancer.  The younger a woman is when she is initially is exposed to alcohol increases her individual odds of developing breast cancer.  Additionally there is a dose-response relationship with breast cancer risk and alcohol consumption.  Women who drank 15g of alcohol a day, which is more than one drink, had a significantly higher risk for breast cancer.  The risk related to such alcohol consumption alone is higher than the risk of having a family history of breast cancer.  (Colditz 1995)
 

Exercise

     It is not only what you ingest into your body that can influence breast cancer prevention, but also what you do with your body.   Female athletes have a reduced risk of breast cancer.  (http://www.cancer.org/bcn/report.html)   Additionally, women who get into the habit of exercising on a regular basis have a better chance at fighting the odds.  "Women who participate in four or more hours of physical activity per week during their reproductive years reduce their risk of breast cancer by 60 percent, compared to inactive women."  (http://oncolink.upenn.edu/cancer_news/1994/excersize_bc.html)   The most significant reduction in risk was associated with women jogging, swimming laps, or playing tennis.  It was also shown that regular exercise, even though possibly only a couple hours a week, also helps to reduce a woman's risk of developing breast cancer.
 

    Conclusion

    Recommendations for preventing breast cancer would include many aspects of a person's behavior.  A low fat diet is strongly suggested, and no more than 30% of total calories should be calories from fat.  A diet with only 20% of its calories coming from fat is a reasonable goal.  In addition to limiting fat intake, it is important to increase consumption of carbohydrates and fiber.  Fruits and vegetables should replace fatty foods in one's diet.  Foods with  complex carbohydrates, fruits and vegetables not only contain antioxidants, but also quite a bit of fiber.  Cuciferous vegetables should also become part of one's diet.  Fish is a healthy alternative that often has less fat than other meats.  Additionally its oil can be beneficial for preventing breast cancer.  Consumption of alcohol should be minimal.  Exercise should become part of a daily routine, and one should try and be active at least four hours a week.
    There is quite a bit of evidence concerning prevention of breast cancer, and numerous studies are currently being run across the country.  Unfortunately many American women think only of screening for breast cancer, not preventing it.  Clearly screening is critical for early detection, but most women do not realize they may have a chance at decreasing their odds for developing breast cancer by modifying their behavior.  During a telephone survey in 1995, only 23% of the women cited dietary factors such as reducing fat and increasing fruits, vegetables, and fiber as a way of reducing their personal risk for breast cancer.  (Barnard 1997)
    There is no doubt eating a low fat diet is related with overall good health, and more and more studies are revealing the positive outcomes dealing with breast cancer prevention as well.  The behavioral aspects of everyday life must not be forgotten when one considers her personal risk for breast cancer.  There is reason why countries have such a varied number of breast cancer incidences.  Thus, behavioral and environmental factors must be considered along with genetics in regards to breast cancer risk assessment and prevention.

Bibliography

Barnard, N.D., and A. Nicholson.  "Beliefs about Dietary Factors in Breast Cancer
     Prevention among American Women, 1991 to 1995."   Preventive Medicine 26
    (1997) : 109-113.

Boyd, N. F., G. A. Lockwood, C. V. Greenberg, L. J. Martin, and D. L. Tritchler.
    "Effects of a low-fat high carbohydrate diet on plasma sex hormones in pre-menopausal women:
    results from a randomized controlled trial."  British Journal of Cancer  76 (1997)  127-135.

Coldritz G. A. and A. L. Frazier.  "Models of Breast Cancer Show that Risk is set by Events
    of Early Life: Prevention Efforts Must Shift Focus."  Cancer Epidemiology, Biomarkers &
    Prevention.  4  (1995)  567-571.

Kimmick, G.G.,  R.A. Bell, and R.M. Bostick.  "Vitamin E and Breast Cancer: a review."
   27  (1997)  109-117.
 

 

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