(RxWiki News) A woman diagnosed with breast cancer has a 90 percent chance of surviving five years, but long-term survival depends on many factors. A healthy diet may be one of those factors.
In the face of a breast cancer diagnosis, many women make healthy lifestyle changes. To look for changes women can make that might reduce their risk of dying after a cancer diagnosis, a research team looked at the effect of diet quality on survival.
These researchers found that a better quality diet reduced the risk of death among women with breast cancer. This risk was reduced even further in those with estrogen receptor-positive (ER-positive) breast cancers.
"Work with a dietitian to develop a healthy diet for you."
Stephanie M. George, PhD, MPH, MA, from the Division of Cancer Control and Population Sciences at the National Cancer Institute in Bethesda, MD, and a team of researchers conducted this study.
The participants for this study came from the Women’s Health Initiative (WHI) program, a large study of women's health issues.
Dr. George and team used data on women who were part of the Dietary Modification Trial of the WHI and some from the observation group, who had no dietary modification. In all, there were 2,319 women aged 50 to 79 in the study, and all of them had been diagnosed with invasive breast cancer.
As part of the WHI, a food frequency questionnaire was completed by the study subjects to collect data on food eaten, amount eaten and frequency. The researchers used the questionnaires completed just before the subjects’ diagnosis and another about 1.5 years later, then once every three years for nine years.
The research team calculated diet quality from the answers on the food questionnaire, using the 2005 US Dietary Guidelines for Americans. Based on a 2,000-calorie diet, a healthy diet was considered one that included or exceeded the recommended consumption of 4 servings of fruit, 5 servings of vegetables, 6 ounces of grains (half of which is whole grain), 5.5 ounces of meat or beans, 3 cups of dairy and no more than 6 teaspoons of oils. The diet recommended that solid fats, alcohol and sugar should be consumed in moderation.
The Healthy Eating Index, which the researchers used for this study, provides scores for eating certain types of foods. Total scores range from 0-100, where a higher score is a better diet.
The researchers scored the food consumed and grouped the participants by score, with a poor quality diet being a score of 34-63, a mixed quality diet falling between 63 and 77 and the better quality diet being a score over 77 points.
Women in the poor quality diet group ate more calories, drank more alcoholic drinks and did less physical activity than the women in the better quality diet group.
Results of the study showed that a total of 415 women died during the 9.5 years they were followed. Of these, 188 died of breast cancer and 227 died from other causes.
Women who ate a better quality diet had a 26 percent lower risk of death from any cause than the women who ate a poor quality diet. The risk of death from causes other than cancer in the better diet group was 42 percent lower than that risk among those eating a poor quality diet.
Among women with ER-positive tumors, those who ate a high quality diet had a 45 percent lower risk of dying from any cause than the women who ate a poor diet. In those with ER-negative tumors, diet had no effect on risk of dying.
The authors of this study noted a possible explanation for the different survivals based on ER status and diet. They hypothesized, “One explanation for this finding is that ER+ survivors generally have better prognosis than survivors of ER- breast cancer and thus may be more likely to die of causes other than breast cancer and for these women, postdiagnosis diet quality may play a larger role in promoting longevity.”
One limitation of the study cited by the authors was that diet quality was based on reports from the study subjects and may have been inaccurate. Another was that they did not have data on cancer treatments that could have affected the results of the study.
This research was published in the February issue of Cancer, Epidemiology, Biomarkers and Prevention.
Funding for the Women’s Health Initiative program was provided by the National Heart, Lung and Blood Institute.
The researchers disclosed no conflicts of interest.