Tracing the Elusive Causes of Breast Cancer and Leveraging Dietary Strategies to Prevent It


by Jack Challem

Confronted by an alarming increase in the incidence of breast cancer over the past 50 years, scientists have desperately sought the cause.

They’ve found lots of risk factors from a genetic predisposition to never having had children. But none may be as disturbing as what Devra Lee Davis, Ph.D., has proposed: that breast cancer is caused by dozens of common, synthetic chemicals that mimic the female hormone estrogen.

Doctors have long known that estrogen, a hormone essential for reproduction, causes cells to grow and increases a woman’s risk of breast cancer. They’ve also known that the natural variation in estrogen production among women could not account for most cases of breast cancer.

But what they didn’t figure on until recently was that manmade estrogens—called environmental estrogens or xenoestrogens—can stack the deck against women and increase their estrogen levels by hundreds of times. In fact, until a couple years ago, no one realized xenoestrogens were as common as they are.

"If xenoestrogens do play a role in breast cancer, reductions in exposure will provide an opportunity for primary prevention of this growing disease," Davis observed in Environmental Health Perspectives (Oct. 1993;101:372-7).

Davis, a university researcher who currently serves as a senior advisor to the Department of Health and Human Services, has fingered pesticides, household chemicals, and common plastics as the major estrogen imitators. Few of them existed before World War II.

That’s when U.S. researchers developed the pesticide DDT to kill body lice and prevent typhus among soldiers. After the war, DDT was widely used to kill agricultural insect pests and malaria-carrying mosquitos. It was the first of many synthetic organochlorine compounds—none had previously existed in nature.

Breast Cancer Increases
Within a few years, the incidence of breast cancer began to creep up. In the 1950s, one woman in 20 was at risk of developing breast cancer. Today, one in nine is at risk, and about 46,000 women will die from the disease this year. Likewise, endometriosis, in which uterine cells grow outside the uterus, has increased dramatically.

But the first effects of DDT and other organochlorines were noted in animals, not people. Rachel Carson, in her 1962 book, Silent Spring, sounded the alarm about DDT, which was causing reproductive problems in many species.

Because of its effect on wildlife, DDT was banned from agricultural use in the United States in 1972. However, it remains in the environment—and people’s bodies. It’s also used in many other countries, and produce sprayed with DDT is regularly imported into this country.

As it turned out, the link between organochlorines to breast cancer was discovered by accident. Researchers have long known that estrogen promotes cancer cell growth when it’s added to experimental cell mixtures. But a few years ago, Ana Soto, M.D., of Tufts University noticed that cells stored in plastic dishes were growing as if they had been exposed to estrogen.

She and co-researcher Carlos Sonnenschein, Ph.D., looked for and identified the contaminant as nonylphenol, a chemical used to prevent plastic from cracking. They subsequently demonstrated that nonylphenol made breast tissue grow.

But DDT and nonylphenol are only the tip of the proverbial iceberg. In our modern environment—filled with plastics, electronics, and chemicals—xenoestrogens exist all around us. They include chemicals known to be hazardous, as well as those believed to be safe. Among them are atrazine, the most commonly used pesticide in the United States; polychlorinated biphenyls (PCBs), used in the manufacture of electronics; polycarbonate plastics, which constitute baby bottles and water jugs; chlorine compounds, such as dioxin, used to bleach paper. They’re also found in petroleum by-products, detergents, spermicides, and other chemicals around the house.

Because both natural estrogens and xenoestrogens are fat soluble, they gravitate to where women have a lot of estrogen receptors and fat—namely, the breasts. Xenoestrogens can also accumulate over a lifetime and be passed through the placenta from mother to fetus, and even through breast milk.

They inflict damage in several ways. First, xenoestrogens bond with estrogen receptors just like a woman’s own estrogen, called estradiol, does. When they attach to the receptors, they transmit a molecular message that tells breast cells to grow larger and to create new cells, much as they would during pregnancy. Second, estrogens prompt the body to release a chemical called "tumor growth factor." Third, xenoestrogens can even increase the number of receptors, which act like estrogen magnets.

It doesn’t take much of a xenoestrogen to trigger a response. For example, heated polycarbonate plastics release an estrogen building block called bisphenol-A (BPA) that’s hard to measure in concentrations less than 10 parts per billion. But only 2 to 5 parts per billion of BPA can prompt more noticeable estrogenic effects in laboratory experiments, according to an article in Science News (July 3, 1993;144:10-13).

The effects are magnified when xenoestrogens are added together. "The cumulative effect may be much greater than any individual molecule," David Feldman, M.D., of Stanford University told the Journal of the American Medical Association (Feb. 9, 1994;271:414-16).

The Link to Breast Cancer
Meanwhile, Davis has built a strong case linking xenoestrogens to cancer. She found that women have a higher than average risk of breast cancer if they were exposed to xenoestrogens while working in the chemical industry or had high levels of DDT in their breast tissue. She also determined that farmers exposed to pesticides have a high incidence of unusual cancers.

Recently, Mary Wolff, Ph.D., of the Mt. Sinai School of Medicine in New York City established a clear link between blood levels of DDT and PCB and a woman’s subsequent risk of developing breast cancer. By analyzing blood samples from 14,000 women, she found that women with high blood levels of DDE, a by-product of DDT, had four times the risk of developing breast cancer compared with women who had low levels of the chemical. Levels of PCBs were also associated with breast cancer risk, though not as strongly.

"Between 1973 and 1980, the incidence of breast cancer in the United States increased a modest 8.0% among women under 50 years of age, while it rose 32.1% among women in the age group 50 years or older," Wolff wrote in the Journal of the National Cancer Institute (April 21, 1993;85:648-52). "Although this increase can be explained in part by enhanced screening, the upward shift is also consistent with the historical pattern of accumulation of organochlorine residues in the environment; i.e., older women who had the greatest potential cumulative exposure to DDT between 1945 and 1972 may now experience a higher risk of breast cancer than woman much older or younger who were not similarly exposed."

The significance of xenoestrogens in breast cancer is still being hotly debated in scientific circles—as it probably will be for several years. For example, a follow-up study described in the Journal of the National Cancer Institute (April 20, 1994;86:589-99) failed to confirm the association between organochlorine compounds and breast cancer.

Still, many researchers point to diethylstibetrol (DES) as the best example of what xenoestrogens are known to do. DES a drug given to women from 1948 to 1971 to prevent miscarriage and, also, to cattle as a growth hormone. It’s now been banned in the United States.

While the women who took DES didn’t suffer any apparent harm, their children did. A small but significant number of DES daughters under the age of 30 developed a rare form of cancer, called clear-cell vaginal adenocarcinoma. Others were born with reproductive abnormalities that left them sterile. DES sons have had a higher than average incidence of undescended testicles, decreased sperm counts, and an increased risk of testicular cancer and prostate problems, according to Lovell A. Jones, M.D., director of the University of Texas M. D. Anderson Cancer Center.

Natural Estrogens May Protect
There are, however, several strategies that might reduce the dangers of elevated estrogen, whether it’s produced by a woman’s body or is the result of pesticide or other chemical exposure.

Natural plant estrogens—called phytoestrogens—may prevent xenoestrogens from attaching to a woman’s estrogen receptors. Like a key in a lock, a phytoestrogen may prevent far more dangerous xenoestrogens from entering cells.

"Scientists first became interested in the possible effects of phytoestrogens when they observed that Japanese women have very low rates of breast cancer, but when they move to the U.S. and adopt a Western diet, their breast cancer rate matches that of the average U.S. population," explained Bette Hileman in Chemical and Engineering News (Jan. 31, 1994:19-23).

"The situation is similar with prostate and colon cancer," she added. "Countries with diets rich in fiber and the phytoestrogens—isoflavonoids and lignin—have few breast, prostate, and colon cancer deaths. Flax seeds, whole wheat, and rye are abundant sources of lignins. Soy beans are good sources of isoflavonoids."

Another phytoestrogen, found with flavonoids in orange peels, shows promise in the treatment of breast cancer. Michael Gould, Ph.D., of the University of Wisconsin, Madison, has used the substance, called limonene, to treat implanted human breast cancers in mice. Sixty percent of the mice receiving limonene had a complete disappearance of tumors, and 20 percent benefited from some tumor shrinkage, he explained at a May 1993 meeting of the American Association for Cancer Research in Orlando, Fla.

B-Vitamins, Other Nutrients Also Protect
Another protective factor might involve how efficiently the liver breaks down estrogen. For example, the liver can break estrogen down into either a weak estrogen, which is safe, or into a strong one capable of damaging deoxyribonucleic acid (DNA) and initiating precancerous changes. According to Hileman, DDT, DDE, atrazine, and other pesticides depress the liver’s mechanism that weakens estrogen while promoting production of the stronger, more dangerous estrogen.

In the early 1980s, nutrition educator Carlton Fredericks, Ph.D., reported that high intake of the B-complex vitamins, plus extra choline and inositol, helped the liver break down estrogen into estriol, a non-carcinogenic form of the hormone.

"Not only does inadequate intake of these vitamins interfere with the breakdown of female hormone by the liver, but estrogen itself may cause vitamin B-complex deficiency," Fredericks astutely noted in an article in the January 1984 Let’s Live.

Fredericks made an especially keen observation. In experiments, he demonstrated that these B-vitamins also reduced many symptoms of premenstrual syndrome—itself caused by excessive estrogen—and probably reduced a woman’s long-term risk of developing breast cancer.

Other nutrients exert a protective effect as well—even in the face of high xenoestrogen exposure. For example, the Inuit of northern Quebec eat the fat of seals and beluga whales, which are loaded with DDT and PCBs. Not surprisingly, Inuit mothers have among the highest concentrations of these chemicals in their breast milk, which can cause brain damage in infants. Yet Inuit children appear to develop normally.

Pierre Ayotte, M.D., of Laval University Hospital in Ste.-Foy, Quebec, believes that omega-3 essential fatty acids may offer protection, according to an article in Environmental Health Perspectives (Dec. 1993;101:618-20). The omega-3 fatty acids, also known as "fish oils," are found in the seal and whale fat, and passed from mother to infant through nursing.

Ayotte’s view has been confirmed in laboratory experiments. David Rose, M.D., Ph.D., of the American Health Foundation, Valhalla, N.Y., recently reported that the omega-3 fatty acids suppressed breast cancers in mice, whereas the omega-6 fatty acids promoted their growth. "Dietary intervention trials to reduce recurrence risk in the postsurgical breast cancer patient should take account not only of the level of fat consumed, but also its fatty acid composition," Rose wrote in the Journal of the American Cancer Institute (Nov. 3, 1993)85:1743-47).

Garlic may also be a potent protector against breast cancer. John Milner, Ph.D., of Pennsylvania State University, University Park, found that high-garlic diets slowed breast tumor growth and reduced the number of tumors in laboratory animals. "The total tumor number was reduced by 56% in rats fed the 2% garlic powder diet throughout the 20 weeks feeding period compared to control-fed rats," Milner explained in Carcinogenesis (Oct. 1992;13:1847-51).

Perhaps the most remarkable recent finding relates to Coenzyme Q10, a vitamin-like substance produced by the body and almost universally found in foods (although it’s highest in organ meats and tuna). CoQ10 is a potent stimulator of the immune system; it promotes energy at the cellular level and functions as an antioxidant.

At the Eighth International Symposia on CoQ10, held in Stockholm in November 1993, researchers from Sweden and the United States reported that breast cancer patients had lower than average blood levels of CoQ10. One of the presenting researchers, Karl Folkers, M.D., Ph.D., of the University of Texas, Austin, treated 32 breast cancer with 90 mg. daily of CoQ10. Six of them showed partial tumor regression, according to Folkers report in Biochemical and Biophysical Research Communications (Mar. 30, 1994;199:1504-8).

"In one of these 6 cases, the dosage of CoQ10 was increased to 390 mg. In one month, the tumor was no longer palpable and in another month, mammography confirmed the absence of tumor," Folkers wrote. "Encouraged, another case having a verified breast tumor, after non-radical surgery and with verified residual tumor in the tumor bed, was then treated with 300 mg. CoQ10. After 3 months, the patient was in excellent clinical condition and there was no residual tumor tissue."

Have We "Poisoned Our Nest?"
Even though some dietary factors protect against breast cancer, it only makes sense to limit one’s exposure to suspected cancer-causing chemicals. There are many ways to do this.

For example, many common plastics contain xenoestrogens. If you drink bottled water, buy it in glass containers instead of plastic. Likewise, when you store food, put it into glass bowls rather than plastic containers.

Around the house, minimize your exposure to synthetic chemicals, including detergents. Instead, use soaps and natural cleansers. And outside, be judicious in your use of pesticides because many of them function as xenoestrogens.

In a syndicated newspaper column, Linda Ellerbee asked whether the increase in cancer was because "we have poisoned our nest." If we have, it’s up to us to make it livable again.

Of Related Interest...
Other Risk Factors in Breast Cancer

One reason scientists are intrigued by xenoestrogens is that 70 percent of breast cancer cases are not preceded by the established risk factors. The six accepted risk factors are :

• a family history of breast cancer,
• onset of menstruation before age 12,
• beginning menopause at a late age,
• giving birth after age 30 to your first child,
• never giving birth, and
• being 40 percent above normal weight for your age and height.

Over the past couple of years, scientists have added and subtracted some new risk factors. For example, fat consumption used to be considered a risk factor. It isn’t any more although meat consumption now is. Paolo Toniolo, Ph.D., of the New York University Medical Center, reported in Epidemiology (July 1994) that women who ate red meat every day were twice as likely to develop breast cancer as woman who ate mostly fish, poultry, and dairy for animal protein.

Weight gain around age 30 increases the long-term risk of breast cancer, according to Noreen Aziz, Ph.D., who presented her findings in May 1994 at a meeting of the American Society for Clinical Oncology in Tampa, Fla. According to Aziz, a 10-pound increase raises risk by 23 percent, a 15-pound increase by 37 percent, and a 20-pound increase by 52 percent.

Smoking also increases a woman’s risk of breast cancer. In an analysis of 600,000 women, Eugenia Calle, Ph.D., of the American Cancer Society found that risk increased with the number of cigarettes smoked. She reported in Epidemiology (May 15, 1994) that women smoking between 20-29 cigarettes a day were 32 percent more likely to die from breast cancer, and women smoking more than 40 cigarettes a day were 75 percent more likely to die from the disease.

Even exposure to electromagnetic fields, a cause of leukemia in children, might increase a woman’s likelihood of developing breast cancer. Dana Loomis, Ph.D., of the University of North Carolina, Chapel Hill, compared death certificates of women employed in electrical trades to those who had other professions.

According to Loomis’ report in the Journal of the National Cancer Institute (June 15, 1994;86:921-25), he found that women who worked as electrical engineers, electricians, power-line workers, and telephone repairers had a 38 percent greater risk of dying from breast cancer.

Copyright 1994 by Jack Challem, The Nutrition Reporter™
All rights reserved. Used with permission.