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For Breast Cancer Survivors,
Soy is Protective and Alcohol is Harmful

Two new studies have examined the effects of certain dietary factors on recurrence of breast cancer in survivors. Soy had protective effects, and alcohol had detrimental effects.



Soy and breast cancer recurrence

Soybeans are rich in isoflavones, a type of phytoestrogen.

Phytoestrogens are plant substances that are chemically similar to estrogen and thus can bind estrogen receptors. Phytoestrogens may block estrogen's natural effects or actually have weak estrogen-like effects in the body. Since estrogen exposure had been known for many years to negatively influence breast cancer risk, soy was thought by some to be potentially dangerous. This fear of soy was unfounded. Isoflavones were actually shown to have anti-cancer effects in cell culture and animal studies.1 Also, in Asian countries where soy is a staple food, rates of breast cancer have traditionally been much lower than those in the U.S.. This paradox launched much debate and hundreds of studies on the relationship between soy and breast cancer. Today, a search of U.S. National Library of Medicine for "soy" and "breast cancer" returns 373 articles from scientific journals.

These most recent and reliable clinical studies support a strong protective effect of soy against breast cancer. Unfortunately the myth that soy contributes to breast cancer has persisted in spite of this plentiful contradictory evidence:

• 2006: A meta-analysis in the Journal of the National Cancer Institute examining data from 18 studies on soy and breast cancer that were published between 1978 and 2004 concluded that soy overall has a protective effect.2

• 2008: A meta-analysis in the British Journal of Nutrition compiling data from 8 different studies (not included in the 2006 meta-analysis) also concluded that soy consumption decreases breast cancer risk. These effects were dose-dependent – a 16% reduced risk for each 10 mg of soy isoflavones consumed daily.3

• 2009: There were reports in Cancer Epidemiology4 and The American Journal of Clinical Nutrition5 that soy consumption during childhood (60% reduced;) and teenage years (40% reduced;) reduce risk of breast cancer in adulthood. Both studies also reported reduced risk for adulthood consumption of soy.

Despite all this evidence about breast cancer prevention, many scientists and physicians continued to doubt the safety of soy for current or previous breast cancer patients, because of soy's phytoestrogen content.

A new study of breast cancer survivors has shown that these doubts are unwarranted as well. Premenopausal breast cancer survivors who consumed more soy had a 23% reduced risk of recurrence.6

Which soy products are most beneficial?
In Asian countries, the average daily intake of soy isoflavones is 25-50 mg, and is consumed via tofu, soybeans, soy milk, miso, and natto. In the U.S., the average soy isoflavone intake is less than 1 mg, and most of this amount is consumed via soy-based additives or isolated soy protein in processed foods. Cruciferous vegetables are the most powerful anti-cancer foods. In addition, Dr. Fuhrman also recommends consuming a variety of beans, including soybeans, as components of an anti-cancer diet.

Minimally processed soy foods:

• Whole soybeans or edamame
• Tofu
• Tempeh
• Unsweetened soymilk

As little as 10 mg of soy isoflavones consumed per day has a protective effect with regard to breast cancer – this equates to approximately 1 ounce of one of these soy foods.

Alcohol and breast cancer recurrence

In contrast to the mainstream assumption that alcohol is heart healthy (http://www.diseaseproof.com/archives/debunking-diet-myths-eat-for-health-red-wine-for-heart-health.html), even moderate amounts of alcohol are associated with increased risk for breast cancer.7

The current study of breast cancer survivors showed that women who consumed 3-4 alcoholic drinks per week were 34% more likely to experience a recurrence than the women who had less than 1 drink per week. This study was presented last week at the San Antonio Breast Cancer Symposium.8

Alcohol has no beneficial effect on the cardiovascular system, it only inhibits the blood's clotting mechanisms. Since breast cancer is the second leading cause of death in women (second to cardiovascular disease), Dr. Fuhrman recommends minimizing alcohol consumption in order to reduce this risk.

Read "Dr. Fuhrman on Breast Cancer"
to learn more diet and lifestyle strategies for breast cancer prevention.



References:
1. Sarkar FH, Li Y. Soy isoflavones and cancer prevention. Cancer Invest
2003 ; 21 : 744 – 57.
2. Trock BJ et al. Meta-analysis of soy intake and breast cancer risk. J Natl Cancer Inst. 2006 Apr 5;98(7):459-71.
3. Wu AH et al. Epidemiology of soy exposures and breast cancer risk. British Journal of Cancer (2008) 98, 9– 14
4. Korde LA et al. Childhood Soy Intake and Breast Cancer Risk in Asian American Women. Cancer Epidemiology, Biomarkers & Prevention April 2009 18; 1050
5. Lee S et al. Adolescent and adult soy food intake and breast cancer risk: results from the Shanghai Women's Health Study. Am J Clin Nutr 89: 1920-1926, 2009
6. Guha N et al. Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study. Breast Cancer Res Treat. 2009 Nov;118(2):395-405. Epub 2009 Feb 17.
7. Lew JQ et al. Alcohol and risk of breast cancer by histologic type and hormone receptor status in postmenopausal women: the NIH-AARP Diet and Health Study. Am J Epidemiol. 2009 Aug 1;170(3):308-17. Epub 2009 Jun 18.
8. http://www.medpagetoday.com/MeetingCoverage/SABCS/17444

 

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