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.

Design: multi-institutional randomized controlled trial. Participants: 3088 women previously treated for early-stage breast cancer; age at diagnosis 18–70 years; diagnosed with stage I–IIIA within the past 4 years; underwent axillary dissection and total mastectomy or lumpectomy with radiation; no current or planned chemotherapy; no recurrent disease or other cancer in past 10 years. Enrollment 1995–2000; follow-up through June 1, 2006.

Intensive dietary pattern: daily targets of 5 vegetable servings plus 16 oz vegetable juice; 3 fruit servings; 30 g fiber; and 15% to 20% of energy from fat; delivered primarily by telephone counseling with 12 cooking classes in year 1 and monthly newsletters; duration through the study follow-up (mean about 7.3 years).

Dietary changes achieved in the intervention group markedly improved diet quality (vegetables +65%, fruit +25%, fiber +30%, fat energy −13%; plasma carotenoids higher by 73% at 1 year and 43% at 4 years) but did not reduce invasive breast cancer events or all-cause mortality over mean 7.3 years (invasive events: 256/1537 vs 262/1551; HR 0.96, 95% CI 0.80–1.14, P=.63; deaths: 155/1537 vs 160/1551; HR 0.91, 95% CI 0.72–1.15, P=.43). No significant interactions by baseline characteristics. Conclusion: Adoption of a diet very high in vegetables, fruit, and fiber and low in fat did not reduce recurrence or death among survivors; diet quality improved but prognosis was not altered over the follow-up period.

Limitations: results may not generalize to broader populations given ~85% White sample and only 14% minority groups; did not assess concurrent exercise or weight loss; dietary intake largely self-reported though validated by biomarkers; not powered to detect small subgroup effects; applicable mainly to survivors of early-stage breast cancer and may not extend to other groups.