Over the years, many studies have suggested that cancer patients who adopt a more healthful diet are more likely to survive. Two new studies prove it.
The Women’s Intervention Nutrition Study (WINS), sponsored by the National Cancer Institute, followed 2,437 women who had previously been treated for breast cancer.1 Half the women continued their regular diets. The other half cut their fat intake. After five years, 12.4 percent of the women eating their usual diets had a cancer recurrence. But the recurrence rate was cut to 9.8 percent in the low-fat diet group, a 24 percent reduction. For estrogen-receptor-negative tumors, the reduction was 42 percent.
Another study, The Women’s Healthy Eating and Living (WHEL) Study, focused on vegetable and fruit intake. Based at the University of California, San Diego, the project included 3,109 women previously treated for breast cancer.2 Half the participants were asked to consume at least five fruit and vegetable servings per day. The remaining participants were asked to push their diet changes further, up to eight fruit and vegetable servings per day. Specifically, that meant five vegetable servings and three fruit servings, plus 16 ounces of vegetable juice. They were also asked to trim their fat intake to 15 to 20 percent of calories.
The study’s first finding was a confirmation that diet changes can alter the hormones that fuel breast cancer. Estrogen levels were noticeably lower in the eight-a-day group after the first year.3 The reason, apparently, is fiber. It has long been known that the liver filters estrogens from the bloodstream, sending them into the intestinal tract where fiber escorts them out with the wastes. That is important, because excess estrogens fuel cancer growth. When the diet is rich in fiber, this hormone-removal system works efficiently. But if the diet is lower in fiber, some of the waste hormones are reabsorbed from the intestinal tract back into the bloodstream.
In a 2005 article, the WHEL investigators found that participants with the highest carotenoid concentrations in their blood—showing that they really were eating their vegetables and fruits—had a 43 percent lower risk of either cancer recurrence or a new primary breast cancer, compared with women whose carotenoid levels were lower.4
In 2007, the Journal of Clinical Oncology published findings from the WHEL research team showing that women in the five-a-day group who followed the five-a-day guideline and were also physically active had nearly a 50 percent reduction in the risk of dying over the next seven years, compared with women who did not meet these healthful guidelines.5 A subsequent JAMA report showed that those in the eight-a-day group did not experience additional benefits beyond those achieved by the five-a-day group.6
When the JAMA report was released, many newspapers misinterpreted the results. USA Today reported, “A diet high in vegetables and fruits apparently does nothing to prevent breast cancer from returning….” Similarly, ABC News declared, “There are many things a breast cancer survivor can do to keep her cancer at bay—but eating a diet that is high in fruits and vegetables isn’t one of them, new research suggests.”
Both got it exactly wrong. The truth was that high fruit and vegetable intake, plus regular exercise, had a dramatic effect on survival, cutting mortality nearly in half. But a woman already eating five vegetable and fruit servings daily gains no further long-term benefit from eating even more vegetables and fruits.
There were several things the WHEL Study did not test. Because most participants did not trim fat intake beyond the first year, the study could not test the value of a low-fat diet. Nor did it test weight loss, something shown to be of benefit in other studies. The study also did not test a vegan diet, which was previously shown to be dramatically effective for prostate cancer patients.7
So, would a diet that combines all these elements yield stronger results than were seen in the WINS and WHEL studies? It may well, and there is certainly reason to make these healthful changes. Taken together, these studies show that women who have been treated for breast cancer can help keep cancer from coming back by reducing fat intake, boosting vegetable and fruit consumption, and remaining physically active.
1. Chlebowski RT, Blackburn GL, Thomson CA, et al. Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women’s Intervention Nutrition Study. J Natl Cancer Inst. 2006;98:1767-1776.
2. 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. Contr Clin Trials. 2002;23:728-756.
3. Rock CL, Flatt SW, Thomson CA, et al. Effects of a high-fiber, low-fat diet intervention on serum concentrations of reproductive steroid hormones in women with a history of breast cancer. J Clin Oncol. 2004;12:2379-2387.
4. Rock CL. Flatt SW, Natarajan L, et al. Plasma carotenoids and recurrence-free survival in women with a history of breast cancer. J Clin Oncol. 2005;23:6631-6638.
5. Pierce JP, Stefanick ML, Flatt SW, et al. Greater survival after breast cancer in physically active women with high vegetable-fruit intake regardless of obesity. J Clin Oncol. 2007;25:2345-2351.
6. 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.
7. Ornish D, Weidner G, Fair WR, et al. Intensive lifestyle changes may affect the progression of prostate cancer. J Urol. 2005;274:1065-1069.