|Modest Dietary Changes Are Not Enough to Prevent Breast Cancer Recurrence
The Women’s Healthy Eating and Living (WHEL) Study was a randomized controlled trial that was designed to test whether adhering to a diet high in vegetables, fruits, and fiber would reduce the risk of recurrence in breast cancer survivors. The study was conducted from 1995-2006, and the subjects were 3,088 women who had been treated for early stage breast cancer. Women were either in a control group or an intervention group.
The daily dietary goals given for the intervention group in the WHEL study were as follows:
- 5 servings of vegetables
- 16 ounces of vegetable juice
- 3 servings of fruit
- 30 g of fiber
- 15-20% of calories from fat.1
The overall results of the WHEL study were published in 2007 and were disappointing. Women in the intervention group on average increased their vegetable intake by 65%, their fruit intake by 25%, and their fiber intake by 30%; they also decreased their energy percentage from fat by 13%. However, there were no significant differences in the number of breast cancer recurrences or deaths between the control and intervention groups.2
Why did this intervention fail?
There were likely many contributing factors. This dietary intervention was started after the women had already been diagnosed and treated for breast cancer. After eating the Standard American Diet for decades and developing cancer; moderate dietary improvements at that point may be too late to prevent recurrence. The dietary advice was likely not specific enough or rigorous enough to have a significant effect. For example, vegetables with breast cancer preventive properties, such as cruciferous vegetables and mushrooms, were not emphasized over starchy vegetables—women were simply advised to eat 5 servings of vegetables daily. Plus, 75% of the women were already consuming 5 servings of vegetables daily before being randomized to control or intervention groups.2
Women were not instructed to eat less of anything except fat or to decrease their caloric intake—so it is unsurprising that there was no significant change in body weight in the intervention group.2 This is an important issue, since excess weight is strongly linked to breast cancer risk.3-7 Plus, these women were also consuming significant amounts of animal protein, which increases cancer risk by increasing IGF-1.8-11
Another potential issue was the advice to reduce percentage of calories from fat, but no advice on limiting refined carbohydrates. Advising women to decrease their calories from fat without direction on what to replace those calories with likely resulted in the women choosing more pasta, rice, white potatoes, bread, and low fat processed foods. These women received no guidance on limiting refined carbohydrates, which is an important point here. Refined carbohydrates are higher in glycemic index and contain less fiber and more starch compared to natural carbohydrate foods. High dietary glycemic index is known to be associated with increased breast cancer risk.12 In contrast, consuming high-fiber foods increases the excretion of estrogen and decreases breast cancer risk.13-15 Now, new research coming out of the original WHEL data suggests that starch intake may play a role in breast cancer risk as well.
Starch intake and breast cancer recurrence
In research presented at the San Antonio Breast Cancer Symposium in December 2011, data from the WHEL Study were re-analyzed with respect to changes in carbohydrate intake. Women from both the control and intervention groups were included in the analysis.
The subjects were arranged into four groups based on how much their starch intake changed over the first year of the study: in the group who had the greatest decreases in starch intake, the likelihood of recurrence was 9.7%; in the group with the greatest increases in starch intake the likelihood of recurrence was 14.2%.16,17 The women who increased their starch intake were at greater risk of recurrence.
Although this particular study did not investigate specific foods, we know that white rice, white flour products, and white potatoes are some of the highest starch foods—these are also low nutrient, high glycemic foods and staples in the Standard American Diet. Breast cancer survivors and all women who want to prevent breast cancer must focus on protective foods such as mushrooms, green vegetables, beans, and onions (G-BOMBS); and avoid low-nutrient disease-causing foods, like refined starches and sugars, animal products, and oils. Too often, researchers do not study dietary patterns with the best anti-cancer potential.
1. Pierce JP, Faerber S, Wright FA, et al: A randomized trial of the effect of a plant-based dietary pattern on additional breast cancer events and survival: the Women's Healthy Eating and Living (WHEL) Study. Control Clin Trials 2002;23:728-756.
2. Pierce JP, Natarajan L, Caan BJ, et al: Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer: the Women's Healthy Eating and Living (WHEL) randomized trial. JAMA 2007;298:289-298.
3. American Institute for Cancer Research. New Estimate: Excess Body Fat Alone Causes over 100,000 Cancers in US Each Year [http://www.aicr.org/site/News2/153571380?abbr=pr_&page=NewsArticle&id=17333&news_iv_ctrl=1102]
4. Trentham-Dietz A, Newcomb PA, Storer BE, et al: Body size and risk of breast cancer. Am J Epidemiol 1997;145:1011-1019.
5. Ballard-Barbash R, Schatzkin A, Taylor PR, et al: Association of change in body mass with breast cancer. Cancer Res 1990;50:2152-2155.
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7. Parker ED, Folsom AR: Intentional weight loss and incidence of obesity-related cancers: the Iowa Women's Health Study. Int J Obes Relat Metab Disord 2003;27:1447-1452.
8. Rinaldi S, Peeters PH, Berrino F, et al: IGF-I, IGFBP-3 and breast cancer risk in women: The European Prospective Investigation into Cancer and Nutrition (EPIC). Endocr Relat Cancer 2006;13:593-605.
9. Hankinson SE, Willett WC, Colditz GA, et al: Circulating concentrations of insulin-like growth factor-I and risk of breast cancer. Lancet 1998;351:1393-1396.
10. Sugumar A, Liu YC, Xia Q, et al: Insulin-like growth factor (IGF)-I and IGF-binding protein 3 and the risk of premenopausal breast cancer: a meta-analysis of literature. Int J Cancer 2004;111:293-297.
11. Shi R, Yu H, McLarty J, et al: IGF-I and breast cancer: a meta-analysis. Int J Cancer 2004;111:418-423.
12. Dong JY, Qin LQ: Dietary glycemic index, glycemic load, and risk of breast cancer: meta-analysis of prospective cohort studies. Breast Cancer Res Treat 2011;126:287-294.
13. Goldin BR, Adlercreutz H, Gorbach SL, et al: Estrogen excretion patterns and plasma levels in vegetarian and omnivorous women. N Engl J Med 1982;307:1542-1547.
14. Zhou Y, Zhuang W, Hu W, et al: Consumption of large amounts of Allium vegetables reduces risk for gastric cancer in a meta-analysis. Gastroenterology 2011;141:80-89.
15. Park Y, Brinton LA, Subar AF, et al: Dietary fiber intake and risk of breast cancer in postmenopausal women: the National Institutes of Health-AARP Diet and Health Study. Am J Clin Nutr 2009;90:664-671.
16. Emond JA, Patterson RE, Pierce JP: Change in Carbohydrate Intake and Breast Cancer Prognosis. In San Antonio Breast Cancer Symposium, vol. Presentation #P3-09-01; 2011.
17. Starch Intake May Influence Risk for Breast Cancer Recurrence. 2011. AACR in the News. http://www.aacr.org/home/public--media/aacr-in-the-news.aspx?d=2654. Accessed December 29, 2011.