Breast Cancer Prevention diet
- Diet high in fresh colorful vegetables and salads plus fish
- Cruciferous vegetable foods (examples broccoli, cabbage, brussel sprouts, collard greens, mustard greens, arugula and kale) - 1-2 cups per day
- High fiber diet (vegetables 5 or more total servings per day and low glycemic fruits like berries)
- Ground flax seeds= 1 Tbsp per day (try adding to organic yogurt, smoothies, or cereal)
- Legumes especially fermented soy foods (miso, tempeh)
- Lower fat in the diet to 20% or less (fat source limited to fish, olive oil, nuts, avocados, and coconuts)
- Avoid non-organic dairy, beef, chicken, turkey, lamb, pork (hormone free-organic-free range meats only!)
- Olive oil 1-2 tbsp/day
- Fish (salmon, tuna, halibut, sardines, mackerel)- at least twice weekly
- Maximize all fruits and vegetables, for mealtimes and for snacks
- Green tea 3-5 cups per day
- Avoid hydrogenated oils (read labels)
- Eliminate sugar and foods made with white flour (no junk food)
- Avoid or minimize alcohol intake
Breast Cancer Prevention with Nutrition
Tori Hudson, N.D.
Professor, National College of Naturopathic Medicine
Medical Director, A Woman’s Time
Author, Women’s Encyclopedia of Natural Medicine
While a large amount of expense and scientific expertise has been expended in the area of breast cancer in the last several decades, these gains are indeed small when observing the ever so small reductions in breast cancer mortality. It is time for the scientific community to consider more seriously the body of evidence pointing towards nutrition as a tool in prevention of breast cancer incidence and mortality. As this information becomes more public, women can finally take advantage of basic and sometimes simple changes in their lifestyle that may profoundly impact their future.
Dietary fat has been the attention of much controversy in regards to its impact on breast cancer. A review of some of the pertinent findings will be helpful. About 30 years ago, the fat intake of many countries was plotted on a graph against breast cancer rates. With few exceptions, the more dietary fat that individuals in that society consumed, the higher the risk of breast cancer. Ten out of ten international studies looking at large differences in fat intake from one country to another continued to confirm this relationship between higher dietary fat levels and higher rates of breast cancer. By and large, the women who live in cultures with the lowest fat intake like Japan and Thailand, have the lowest rates of breast cancer. Women in the middle east who have medium rates of breast cancer have medium amounts of fat in the diet. Women in Europe and North America with the highest intake of dietary fat have the highest rates of breast cancer.
However, in 1992, the Nurses’ Health Study group found no such link. There have been many critiques of this study that have pointed out the inaccuracy of the measurements used and results obtained but perhaps the most compelling at the time was that of the five categories of dietary fat that were analyzed. Its most glaring deficiency was that the group with the lowest amount of fat was still only slightly lower than 29 percent. This is notably higher than the 20 percent many researchers believe to be the beginning of where women would receive the protective benefits.
In March of 1999, a follow up analysis of 88,795 women extended the Nurses’ Health Study for another 6 years and more than 1500 cases. This extended study is now considered large enough and long enough to assess the effect of less than 20% fat intake as well as examining risk of different types of fat. Surprising to many, they saw no increased risk of breast cancer with increased intake of animal fat, polyunsaturated fat, saturated fat, or trans-unsaturated fat . They also found no evidence of decreased risk of breast cancer with increased intake of vegetable fat or monounsaturated fats. Also contrary to the predominant hypothesis, they observed an increased risk of breast cancer associated with omega-3 fat from fish. The strength of this second report is that the analysis was prospective, and included more cases with longer follow-up than the previously studied report. However, the capacity to examine breast cancer risk at the extremes of fat intake is limited by the small proportion of women in those groups and a greater probability of misclassification of dietary intake in these categories.
Numerous other studies have pointed out the protective benefits of olive oil and fish fat. A study published in the Journal of the National Cancer Institute in 1995 demonstrated that increased olive oil consumption was associated with a lowered risk of breast cancer in Greek women by 25%. Two case-control studies, one in Spain and another in Italy, as well as the Greek study are reasonably large, properly analyzed studies of monounsaturated fat and breast cancer. The Spanish study and the Greek study have similar results, suggesting a protective effect of olive oil. The Italian study found a strong positive association between saturated fat intake and breast cancer risk, but no association with monounsaturated fat intake. Another study in France showed a protective effect between breast cancer and the consumption of olive oil, although it was not considered statistically significant. A recent survey was completed in Sweden studying 61,471 women from 1987 to 1990. They reported that monounsaturated fat reduced the risk of breast cancer by 45 percent. They credited the effects of canola oil and olive oil, the oils highest in oleic acid. To achieve optimum protection, 2 tablespoons per day is recommended.
It is still thought by most nutrition experts that one of the best ways to reduce the risk of breast cancer is to consume more omega-3 fatty acids. The protective effect of omega-3 fatty acids was first observed in Greenland Eskimo women who seemed to have a strikingly low rate of breast cancer. These women have a diet that is probably the highest in omega 3 fats of any women to date. Laboratory, animal and epidemiological studies almost universally show reductions in breast cancer associated with high omega 3 fish oils. Fats containing high amounts of omega 3 polyunsaturated fats have been reported to have a suppressive effect on tumor growth in female rats as well as other animal models that have been studied. Fish that are generally available and contain high amounts of omega 3 oils include salmon, tuna, halibut, mackerel, sardines and herring.
It may be that the kind of fats have more to do with breast cancer protection than the amount of fat. It has been difficult to conclusively associate amount or kinds of fat with breast cancer risk because there are many confounding nutritional variables in diets associated with low rates of breast cancer. One of these variables is fiber.
With all the attention on fat, fiber has been underrated as a breast cancer prevention strategy. A low fat diet, rich in insoluble fiber, has been shown to decrease the circulation of estrogens between the intestines and the liver and decrease plasma estrogen levels, thereby potentially reducing the risk of hormone-related cancers. Seeds and whole grains contain significant amounts of lignans. Once lignans are absorbed, they interfere with estrogenic activity and have a weak estrogen blocking effect on the breast. Breast cancer patients excrete lower levels of urinary lignans than healthy women do. The lack of sufficient lignans in the urine is in part due to a low-fiber diet. Vegetarians eat more fiber and more lignans, than do non-vegetarians and vegetarians excrete a high level of lignans. Vegetarians with a high lignan diet do in fact appear to have lower rates of breast cancer. Studies on dietary fiber have however yielded conflicting results. In one of the most recent analyses in June 1998, the International Journal of Cancer published the results of a study of 10,000 women with cancer, who were compared to 8,000 controls without the disease. The investigators concluded that a high intake of whole grain foods consistently reduced the risk of cancer at all sites, except thyroid. The importance of fiber-rich foods in the prevention of breast cancer should not be ignored, although proof of this effect is not yet conclusive.
Most but not all studies report women who drink alcohol have a higher risk of breast cancer compared with women who do not drink. In 1988, researchers conducted a meta-analysis of sixteen previous studies. When the researchers looked at retrospective studies, they found that two drinks per day were associated with a 40 percent increase risk of breast cancer. When they looked at prospective studies, they found that two drinks per day were associated with a 70 percent increase in risk. They also found that in the prospective studies, the more the women drank, the higher their risk. A 20 percent increase was found in women who averaged half a drink per day.
Individual dietary nutrients may be associated with a reduced risk of pre and postmenopausal breast cancer. Dietary sources of vitamin C, carotenes, selenium and vitamin D may be important nutrients to consider in prevention strategies. If you collect the results together of twelve breast cancer/nutrition studies, the women consuming the most vitamin C were found to have a 16 percent reduction in risk of premenopausal and a 37 percent reduction in the risk of postmenopausal breast cancer. It is difficult to know if the protective association is the result of other properties and ingredients found in the fruits and vegetables, which are high in vitamin C, or the vitamin C specifically. Fruit, the best dietary source of vitamin C, by itself has been found to have a link with breast cancer protection. The Nurses’ Health Study could not find a link between vitamin C in food or supplements and breast cancer prevention.
Another valuable antioxidant is vitamin A, which occurs as retinol and beta-carotene. There is evidence that women who eat more beta-carotene or retinol have a lower risk of breast cancer. Both may be potentially able to reduce cancer risk, but most evidence suggests that beta-carotene is more protective. Women who eat the most vegetables in their diet, the best dietary source of beta-carotene, have a lowered risk of breast cancer; maybe as much as a 90 percent lower risk than that of women with the lowest vegetable intake.
Selenium has significant antioxidant properties by activating glutathione peroxidase. Numerous observations have been made regarding selenium and breast cancer. Areas of the United States with low levels of selenium in the soil have higher rates of breast cancer. In some but not all studies, American breast cancer patients have been reported to have lower blood levels of selenium than do healthy women. A more recent study cast serious doubt on the protective relationship between selenium and breast cancer. A double-blind randomized cancer prevention trial supplementing selenium to patients with a past history of non-melanoma skin cancers demonstrated a protective effect with prostate, colorectal and lung cancer, but not breast cancer.
Vitamin D has been used to prevent mammary cancer in rats, inhibit breast cancer cell growth in the laboratory, and may have antiestrogenic activity. Women who live in sunnier parts of the country or in the Southern hemisphere leading to increased levels of sun exposure correlate with reduced risk of breast cancer. When we look at dietary vitamin D though, there may be some correlation with an increased risk of breast cancer. Since dietary sources of vitamin D are high in saturated animal fat, it would seem logical that the dietary source of vitamin D may be problematic.
There are some specific vegetables that may have a very important role in reducing the risk of breast cancer. Cabbage family foods (broccoli, cauliflower, cabbage, brussel sprouts), are high in compounds called indoles, or specifically indole-3-carbinol (I3C). I3C has been reported to affect the metabolism of estrogen in a way that might protect against breast cancer. Animal research and laboratory research have confirmed those same findings. A recent study in Sweden, compared the diets of 2,832 postmenopausal women aged 50-74 years diagnosed with invasive breast cancer with 2,650 postmenopausal women of the same age with no history of breast cancer. Women who consumed an average of 1 ˝ servings of cabbage family vegetables each day had a 25% decreased risk of breast cancer.
Perhaps the most current topic of interest is the relationship of soy to rates of breast cancer. Most of the research we have on soy is in relationship to lowering the risk of breast cancer in women who consume more soy in their diets from a young age (Japanese, Chinese women). In addition, we do have some laboratory research to glean theories from, regarding the safety of using soy products in women who have had or have breast cancer. There is a great deal in the scientific literature that provides support for the conclusion that soy contributes to the prevention of breast cancer. Several studies have observed and concluded that Asian women who consume a traditional low fat, high soy diet have a four to six fold lower risk of developing breast cancer. The soy-derived isoflavones, i.e., genistein and daidzein, protease inhibitors, phytosterols, and saponins are remarkable in their activities against a variety of cancers. Biochemical mechanisms that explain the anticancer action of genistein are numerous. They include the antiestrogenic effects, induction of cell differentiation (the more differentiated a cell, the less likely it is to become cancerous), inhibition of several enzymes that induce cancers, antioxidant effects, and antiangiogenesis (limiting the blood supply to cancer cell sites and tumors). Dietary phytoestrogens also inhibit cancer cell growth by competing with estradiol for the type II estrogen binding sites. Even more convincing evidence for the breast cancer protection benefit of soy comes from animal studies. Soy supplementation has reduced the number and size of tumors that were induced with a carcinogenic substance. A review paper of 26 animal studies of experimental carcinogenesis in which diets containing soy or soybean isoflavones were employed, 17 reported protective effects. No studies reported soy intake increased tumor development. The epidemiological data shows that consumption of nonfermented soy products, such as soymilk and tofu, tended to be either protective or not associated with cancer risk; however no consistent pattern was evident with the fermented soy products, such as miso. Protective effects were observed for both hormone and nonhormone related cancers. Another study that offers some insight evaluated the effects of soy consumption on steroid hormones in premenopausal women. Six healthy women in their 20’s ingested 12 oz of soy milk three times daily for one month. Daily isoflavone intakes were approximately 100 mg of daidzein and 100 mg of genistein. Serum estradiol levels decreased by 31% on cycle days 5-7, 12-14 and decreased by 31 % on days 20-22. Progesterone levels in the second half of the cycle decreased by 35%. Menstrual cycle length extended from 28.3 days to 31.8 days during the one month of soy. These results suggest that consumption of soy diets containing phytoestrogens may reduce circulating ovarian steroids, increase menstrual cycle length, two effects that may account in part for decreased risk of breast cancer. While a statement that soy reduces cancer risk cannot be made with certainty at this time, there is a sufficient amount of evidence to feel comforted in its use as a proactive measure one could take to help lower the risk of breast cancer. (see full TLFD column on soy and breast cancer October 2001
While this article is not attempting to deal with treatment of breast cancer, one study that would be remiss not to mention is on Green tea helping to reduce recurrence rates in women who had stage I and II breast cancers. In the spirit of common sense, it would seem that your average woman who does not have breast cancer and women at higher risk for breast cancer, should drink green tea as a preventive measure.
In this study, 472 women were studied who had invasive breast carcinoma. 117 had stage I, 273 stage II, and 82 stage III and all had undergone a partial or total mastectomy. This survey study was carried on for 9 years from 1984 to 1993. The questionnaire included intake of green tea, coffee, black tea, various food groups such as soy and seaweed and fish and vegetable, cigarettes, alcohol as well as breast tumor characteristics, tumor markers, adjunct treatments, medical history and various physical parameters.
The researchers determined that in stage I and II breast cancer, increased consumption of green tea was associated with less metastasized axillary lymph nodes in premenopausal women and an increased progesterone and estrogen status in postmenopausal women. No such associations were seen in stage III breast cancer patients. The consumption of green tea among the 349 women without a recurrence of breast cancer was significantly higher than among the 123 women with a breast cancer recurrence. In stage I and II patients, there was a 16.7% recurrence rate for those consuming 5 cups or more of green tea (average 8 cups) per day. For those who consumed 4 or less cups per day (average of 2), there was a 24.3% recurrence rate. Disease-free survival was also significantly improved in stage I and stage II breast cancer patients with a greater consumption of green tea. Of all the predictors, green tea was the most statistically significant predictor for a decreased rate of recurrence in the stage I and II patients. No improvement in prognosis was seen in stage III patients.
Green tea (Camellia sinensis) contains several polyphenols including epigallocatechin gallate (EGCG). EGCG enhances antioxidant defense systems as well as being a potent free-radical scavenger. It has also been shown to inhibit the growth of several breast cancer cell lines in the laboratory, inhibit an enzyme called urokinase that is involved in tumor invasion and metastasis and induces programmed cell death. The suggestion is that EGCG found in green tea has multiple anticancer properties.
A possible bias influencing this survey study is that perhaps those individuals who drink so much green tea are also those who are more health conscious. It is also my experience that getting a Western woman to drink an average of 8 cups of anything per day besides coffee or soft drinks is very difficult. However, once these results are shared, advising something as benign and potentially significant as merely drinking tea, may inspire greater compliance. One option might be to use green tea extract in tablet form. It is estimated that one cup of green tea contains 30 to 40 mg of EGCG.
Many will consider these nutritional prevention strategies far too speculative and lacking in sufficient scientific data, especially clinical trials. However, given that one in eight women in the U.S. will be diagnosed with breast cancer in their lifetime, and given the gross lack of understanding as to the cause of breast cancer, those who would take issue with safe, nutritional prevention strategies look only biased in a time of great need for progressive thinking.
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