Soy Slashes Breast Cancer Risk
For the past decade, a controversy has raged over whether people can reduce their risk of cancer by increasing their consumption of soy foods or soy supplements. In response to the debate, a number of studies were initiated in the 1990s to ascertain soy’s effects on human health.
Over the past few years, the results of these studies began to be released. While ignored by the mainstream media, the startling findings indicate that breast (and prostate) cancer risk can be cut in half if people consume more soy.125,211,212
One recent study showed that women who ate a Western-style diet, high in meats and sweets, had nearly twice the risk of developing estrogen receptor-positive breast cancer, compared with women who ate a traditional Asian diet high in soy and vegetables.125 This and other studies provide evidence that compounds found in soy have a breast cancer-preventive effect.
Isoflavones derived from soy have shown great promise in providing natural protection against multiple types of cancer.114-116 Two of the best known soy isoflavones are genistein and daidzein.
Isoflavones exert a number of positive biological effects on the human body, and many practitioners of integrative medicine (and even a small but growing number in mainstream medicine) now believe that consumption of soy and isoflavones can reduce the risk of many chronic diseases, including cancer, heart disease, and osteoporosis.113-116,211-217
Studies conducted in Asia found that breast cancer risk was significantly lower among Asian women who consumed large quantities of isoflavones and other soy products, compared with those who consumed less of these healthful nutrients.115 Because animal studies have shown that a diet high in soy and genistein can protect against breast, colon, and skin tumors, it seemed reasonable to think that soy could also help prevent human cancers and, in particular, breast cancer.218Yet many mainstream medical practitioners remain skeptical that something as simple as soy could have such a profound effect on human health.
Soy isoflavones are correctly classified as selective estrogen receptor modulators.219 Due to their unique molecular structure, soy isoflavones can act as both estrogen receptor agonists and receptor blockers. In fact, elegant biochemical studies have shown that some isoflavones bind to the cancer-protective estrogen beta receptor six to eight-fold more readily than native estrogen.219 With this ability, soy isoflavones are thought by many to confer the beneficial effects of estrogen without its potentially dangerous side effects, especially in hormonally sensitive tissues found in both the breast and endometrium.219
Numerous studies show the potential benefits to women of incorporating soy in their diets to help prevent breast cancer. A landmark case control study of women in Singapore, involving 200 case subjects and 420 control subjects, found that women with the highest consumption of soy-based products had a markedly decreased risk of developing breast cancer.117 Finally, a very large population-based, prospective study of 21,852 Japanese women aged 40-59 found that women with the highest intake of soy isoflavones reduced their risk of breast cancer by up to 54%, compared with women with the lowest intake of soy isoflavones.115
In addition to being a chemopreventive supplement for breast cancer, soy isoflavones are also thought to be effective in warding off other types of cancer that afflict women, including endometrial cancer. A recent case control study reported the effects of soy isoflavones and other phytoestrogens on the risk of developing endometrial cancer.220 The study compared 500 women aged 35-79 who developed endometrial cancer between 1996 and 1999 with 470 age- and ethnicity-matched controls. As in studies examining the effects of isoflavones on breast cancer, this study showed that women with a higher intake of soy isoflavones had a significantly lower risk of developing endometrial cancer. Even more interesting was that the levels of isoflavones needed to provide protection against endometrial cancer were found to be much lower than the amount believed necessary to protect against breast cancer (in fact, they were the amounts that could be obtained from a healthy American-style diet).
Meat Increases Breast Cancer Risk
Studies that look at human populations (epidemiological studies) have consistently shown that what we eat affects our cancer risk. Women who eat more red meat suffer higher breast cancer rates. In one of the better documented studies, postmenopausal women in China who ate a Western-style diet (which included beef, pork, and desserts) were 30% more likely to develop breast cancer than those eating a diet based on vegetables and soy. Even more startling was the finding that in women who developed estrogen receptor-positive breast tumors, those who ate the Western-style diet experienced a 90% increased risk!125 This is in stark contrast to a study that demonstrated a 52% decreased risk of breast cancer in women with the highest intake of vegetables and fruits, compared to the lowest intake.221
However, it’s not known whether meat from “free range” animals (beef, buffalo, wild game, chicken, pigs) also increases breast cancer risk. While even organically raised, grain-fed animals (like commercially raised grain-fed animals) have much more omega-6 (pro-inflammatory) fatty acids than omega-3 (anti-inflammatory) fatty acids, this ratio is reversed in meat from free-range animals, with significantly more omega-3 than omega-6 fatty acids.222 Theoretically, this much more natural ratio should be associated with lower breast (and other) cancer risk, but research still needs to be done on this point.
Fish Oil and Breast Cancer Risk
In addition to fish oil’s well-known cardiovascular benefits, research has revealed that omega-3 rich fish oil might offer protection against breast cancer as well. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the two most important components of fish oil. One investigation documented a 49% decreased risk of breast cancer in women with the highest dietary intake of omega-3 fatty acids, compared to those with the lowest intake. Furthermore, women with the highest red blood cell levels of EPA had a remarkable 73% decreased risk of breast cancer, compared to those with the lowest levels.223
A group of researchers in France compared levels of DHA in breast tissue in 241 patients with breast cancer and 88 patients with non-cancerous benign breast disease. They reported that women with the highest levels of DHA in their breast tissue had a 69% decreased risk of breast cancer, compared to women with the lowest levels of DHA in their breast tissue.224
Why Plant Foods Are So Important
The body is bombarded with carcinogens on a daily basis. These cancer-causing agents include pesticides, overcooked food, alcohol, food additives, tobacco, fungal mutagens, and industrial pollutants. While avoiding carcinogens is difficult, it may be possible to mitigate their lethal effects by providing the body with a specific plant extract that facilitates the detoxification and removal of these dangerous substances from the body.
A compound called D-glucarate is found in grapefruit, apples, oranges, broccoli, and Brussels sprouts.225,226 D-Glucarate has been shown to protect against cancer-causing agents by supporting detoxification and removal of dangerous chemicals, and also by protecting against the mutating effects that these carcinogens induce on cellular DNA.227
There are several mechanisms by which the body detoxifies itself. One way of guarding against toxic overload involves a pathway of detoxification in the body whereby carcinogens are combined with water-soluble substances, thus making them more easily removed from the body. This process is called glucuronidation, and D-glucarate has been shown to support this important detoxification mechanism.227
D-Glucarate functions by inhibiting the beta-glucuronidase enzyme, thus protecting the critical “glucuronidation” detoxification mechanism. One example of the importance of glucuronidation can be seen in the risk factors for breast cancer. Excess levels of 16-alpha-hydroxyestrone and beta-glucuronidase enzyme activity are associated with an increased incidence of breast cancer.228 D-Glucarate is thought to decrease estrogen’s effects by favorably affecting estrogen’s metabolism and elimination.
Research studies have shown that D-glucarate inhibits breast tumor incidence.118,119 One study in rats that already had breast cancer showed that oral D-glucarate administration resulted in a 50% inhibition of beta-glucuronidase, which led to a 30% reduction in mammary tumor growth during the promotion stage and a four-fold reduction in the absolute number of tumors.229 Another report showed a more than 70% decrease in mammary tumor development in rats exposed to carcinogens that were also administered D-glucarate.120 Still another study looked at the effects of D-glucarate on the initiation and promotional stages of mammary cancer. The results showed a reduction of 28% during the initiation stage, while cell replication was reduced by 42% during the promotion stage.121 Inhibition at the initiation stage is a very important part of D-glucarate’s actions, as it reduces the risk that cancer will even start.
Eating lots of the right fruits (grapefruit, apples, cherries) and vegetables (broccoli, Brussels sprouts) supplies the body with D-glucarate, though it is also available in dietary supplements designed to support breast health.
How Lignans Protect the Breast
A number of published studies indicate that dietary lignans may protect against cancer by favorably altering estrogen metabolism, inhibiting angiogenesis, and inducing cancer cells to self destruct.122,123 The greatest support for a role of lignans in cancer prevention has been shown for premenopausal breast cancer.
Researchers in New York assessed breast cancer risk and dietary lignan intake in more than 3,000 women, including about 1,100 patients with confirmed breast cancer and approximately 2,000 cancer-free women who served as controls. The scientists determined that premenopausal women with the highest lignan intake had a 44% reduced risk of developing breast cancer.122
Scientists in Italy suggest a mechanism for the protective effect. Their research indicates that higher blood levels of a phytoestrogen called enterolactone—the primary lignan derived by the body from flaxseed—are associated with a lower risk of breast cancer. Conversely, the researchers noted, “values of serum enterolactone were significantly lower in women who subsequently developed breast cancer,” leading them to conclude that the enterolactone “had a strong protective effect on breast cancer risk.”123
Scientists at the University of Toronto reported that flax lignans can slow down the growth of breast cancer in women. Thirty-two women awaiting surgery for breast cancer were randomized to receive a muffin containing 25 grams of flaxseeds or a muffin that did not contain flaxseed (control group). Analysis of the cancerous tissue after surgery revealed that markers of tumor growth were reduced by 30%-71% in the flaxseed group, while the control group did not experience any reduction in markers of tumor growth. The scientists concluded that “dietary flaxseed has the potential to reduce tumor growth in patients with breast cancer.”230
Lignans may also protect against endometrial cancer, a condition associated with prolonged exposure to unopposed estrogens (this means estrogen administered without progesterone). Researchers in California assessed lignan intake and cancer status among nearly 1,000 women in the San Francisco area and determined that women with the highest dietary lignan intake experienced a promising trend toward a lower risk of developing this carcinoma of the uterine lining.220 The relationship between lignans and endometrial cancer risk reduction was slightly stronger among postmenopausal women.
Based on a lot of favorable publicity, health-conscious people are increasingly adding flaxseed to their diet for the purpose of obtaining the beneficial lignans. Highly concentrated lignan extracts are also available in dietary supplements.
Green Tea’s Anti-Cancer Effects
Green tea is rich in plant compounds known as polyphenols. The most active group of green tea polyphenols is the catechins, particularly epigallocatechin gallate (EGCG). Copious evidence supports a role for these compounds in preventing breast cancer. In laboratory studies, green tea polyphenols and EGCG have been shown to suppress the growth and reproduction of human breast cancer cells.231,232 Of even greater interest, these beneficial compounds in green tea delay the appearance of tumors in mouse models of breast cancer and cut down on the total tumor burden (amount of cancer in the body) when human breast cancer cells are injected into laboratory mice.232,233
Other exciting benefits of green tea include inhibition of vascular endothelial growth factor (VEGF) production,233,234 which cuts off the blood supply needed for tumor growth; down-regulation of estrogen receptor-alpha function in breast cancer cells;235 reduction of tumor invasiveness;233 and increased apoptosis, or programmed cell death, in cancer cells.236
One experiment showed that EGCG, 50-100 mg/kg/day, added to the drinking water of female mice, inhibited growth of breast cancer. After five weeks of EGCG treatment, the weight of breast tumors was reduced by 68% in mice consuming EGCG daily.237
But green tea’s benefits aren’t restricted to animal or laboratory models. An investigation found a 47% decreased risk of breast cancer in women who drank at least 3 cups per day of green tea, compared to those who did not consume any green tea.238
The medical establishment questions the use of bioidentical hormones out of concern about cancer risks. Earlier in this article, we outlined persuasive data showing the anti-cancer properties of estriol and natural progesterone.
When factoring in the potent anti-cancer effects that occur in response to consuming healthy foods (such as broccoli and soy) and supplements (such as vitamin D and fish oil), while avoiding carcinogenic foods (such as sugar and well-done meat), the argument that maturing women should forever be denied their full complement of natural sex hormones does not stand up to scientific scrutiny.