Breast Cancer Survival: Exceeding 5 A Day Veg And Fruit Diet Has No Effect

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Main Category: Breast Cancer
Also Included In: Nutrition / Diet
Article Date: 18 Jul 2007 - 0:00 PDT

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A new large scale US study suggests that women with early stage breast cancer do not reduce recurrence or increase survival when they follow a diet that goes beyond the recommended 5 a Day guidelines on eating fruit, vegetable, fibre and fat.

The study is published in the Journal of the American Medical Association (JAMA).

Dr Marcia Stefanick, one of the senior researchers and professor of medicine at Stanford Research Centre in California said she was surprised and disappointed by their findings but said it did not mean a healthy diet made no difference to breast cancer. This study was looking at the effect of exceeding the guidelines, not following them.

The research formed part of the Women's Healthy Eating and Living (WHEL) Study which is based at the University of California, San Diego and involved scientists from the University of California, Davis, Stanford University, Kaiser Permanente in Oakland and Portland, University of Arizona at Tucson, and the University of Texas MD Anderson Cancer Center in Houston.

WHEL is the largest multi-centre randomized trial to assess the impact of diet on additional breast cancer events.

Another senior researcher, Dr John Pierce, director of the Cancer Prevention and Control Program at the University of California, San Diego, said this study was definitive and that it:

"Provides strong evidence that, for the typical woman diagnosed with early stage breast cancer, there is no additional health benefit over 7 years from dramatically increasing the diet's amount of nutrient-rich plant-based foods, compared to following the recommended healthy diet."

Pierce, Stefanick and colleagues followed over 3,000 patients who had been treated for early stage breast cancer and were aged between 18 and 70 over a period ranging from 6 to 11 years. The participants were randomly assigned to one of two groups: the intervention group and the comparison group.

The intervention group received telephone counselling and newsletters and went to cooking classes that encouraged them to follow a daily diet comprising 5 portions of vegetables, 16 oz (about half a litre) of vegetable juice, 3 portions of fruit, 30 g of fibre, and 15 to 20 per cent of energy intake derived from fat.

The comparison group was given printed leaflets about how to follow the "5 a day" diet promoted by the US Department of Agriculture (USDA).

At first, all the participants were following the 5 a day diet, but as the women in the intervention group were exposed to more information, classes, and counselling, their diet changed to the one they were encouraged to follow. By the end of the first year the women in the intervention group were eating an average of 12 portions of vegetables a day, were eating substantially more fibre and less fat.

Further results showed that:

• The intervention group maintained a significantly different diet over 4 years compared with the comparison group.
• This diet had 65 per cent more vegetables, 25 per cent more fruit, 30 per cent more fibre and 13 per cent less energy intake from fat.
• Tests measuring concentrations of carotenoid (a plant pigment) in the blood confirmed differences in fruit and vegetable intake.
• The women in both groups received similar levels of clinical care throughout the study.
• Over the 7.3 years of mean follow up, 16.7 per cent of the intervention group versus 16.9 per cent in the comparison group had an invasive breast cancer event.
• Also, rate of death in the intervention group was 10.1 per cent compared with 10.3 per cent in the comparison group.
• The figures show a slight favouring toward the intervention group but the adjusted hazard ratios (0.96 and 0.91 respectively) are not statistically significant (P= 0.63 and 0.43).
• These figures were independent of the type of tumour the women had at the start of the study, their demographic characteristics and diet at the start of the study and the way their breast cancer was treated.

The study concluded that:

"Among survivors of early stage breast cancer, adoption of a diet that was very high in vegetables, fruit, and fiber and low in fat did not reduce additional breast cancer events or mortality during a 7.3-year follow-up period."

The researchers said that following such an intensive diet provided no additional benefit compared to following the generally recommended dietary guidelines.

Vicky Newman, Director of Nutrition Services for the Cancer Prevention Program at the Moores Cancer Center at the University of California in San Diego said:

"The dietary changes achieved and maintained by the women in the intervention group resulted in some of the biggest differences in dietary pattern ever reported in a large randomized clinical trial."

"It provides further evidence of the effectiveness of telephone counseling in helping people to change behaviors," she added.

Bette Caan, senior epidemiologist at the Kaiser Permanente Division of Research in Oakland, California said:

"These results do not mean that women should stop paying attention to what they eat."

"In addition to exercising regularly, eating a diet that has plenty of fruits and vegetables and is moderate in fat is still one of the best ways we know to maintain health," said Caan.

The researchers emphasized that this study relates only to breast cancer survivors and they were aware of other good studies are out there showing that following a diet that exceeds the 5 a day guidelines can lower blood pressure and reduce risk of stroke and heart disease.

Also, reflecting on the study's limitations, the researchers pointed out that the results were for a "typical woman" on the study. There may have been subgroups that benefitted from exceeding the 5 a day guideline, and they are going to investigate this further. In addition, the 7 year follow up may not have been long enough for the younger part of the cohort for which longer term outcomes may show more significant benefits, for example from reduction in heart disease risk.

According to the American Cancer Society (ACS), breast cancer is the most common cancer in women, with the exception of nonmelanoma skin cancers.

The chance of a woman in the US getting invasive breast cancer sometime in her life is about 1 in 8; this translates to about 13 per cent of women.

The ACS estimates that in 2007 there will be nearly 178,500 new diagnoses of invasive breast cancer in American women and there are over 2 million breast cancer survivors living in the US. North American women have the highest rate of breast cancer in the world.

"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."
John P. Pierce, Loki Natarajan, Bette J. Caan, Barbara A. Parker, E. Robert Greenberg, Shirley W. Flatt, Cheryl L. Rock, Sheila Kealey, Wael K. Al-Delaimy, Wayne A. Bardwell, Robert W. Carlson, Jennifer A. Emond, Susan Faerber, Ellen B. Gold, Richard A. Hajek, Kathryn Hollenbach, Lovell A. Jones, Njeri Karanja, Lisa Madlensky, James Marshall, Vicky A. Newman, Cheryl Ritenbaugh, Cynthia A. Thomson, Linda Wasserman, and Marcia L. Stefanick.
JAMA 2007;298:289-298.
Vol. 298 No. 3, July 18, 2007

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Written by: Catharine Paddock
Writer: Medical News Today
Copyright: Medical News Today
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