SAN ANTONIO—Women who have survived breast cancer and usually spend at least 13 hours between their last meal of the day and the first meal in the morning appear to have a decreased risk of developing breast cancer, researchers reported at the San Antonio Breast Cancer Symposium.
So if a breast cancer survivor usually eats dinner at 8pm and then had breakfast before 9am, she had a 36 percent greater risk of having a breast cancer “event” than if she finished her last meal of the day at 6pm and didn't eat breakfast until after 7am the following morning, said Catherine Marinac, a PhD candidate at the University of California at San Diego Cancer Center, who presented the data in a poster study titled “Intermittent fasting in breast cancer risk and survivorship: Insight from the women's healthy eating and living study” (Abstract P3-09-01).
“Prolonging the length of the nightly fasting interval may be a simple, non-pharmacologic strategy for reducing the risk of breast cancer recurrence as well as other chronic conditions with etiologic ties to breast cancer such as type 2 diabetes,” she told OT.
She and her colleagues also found that women who fasted less than 13 hours had a greater risk of breast cancer mortality—a 21 percent increase over the women who had intermittent fasting of more than 13 hours, but the difference did not reach statistical significance.
Similarly, there was a 22 percent greater risk of all-cause mortality among women who fasted less than 13 hours, but again that difference did not reach statistical significance.
Mechanism: Sleep & Glucoregulation?
“The mechanisms through which a prolonged nightly fasting interval may improve breast cancer prognosis may involve sleep and glucoregulation,” she said, noting that previous in vivo studies gave hints that fasting could have an impact on recurrent disease.
“Landmark studies in rodents have demonstrated that prolonged intermittent fasting during the sleep phase reduces metabolic dysfunction associated with breast cancer risk. In mice, this eating pattern led to improved glucoregulation; reduced body and mammary fat pad mass; reduced inflammation; and improved regulation of circadian rhythm patterns.
“Data from other rodent models indicate that fasting influences cancer incidence and progression,” she continued, noting, however, that no human studies have examined associations between prolonged nightly fasting and cancer risk.
In an attempt to get at how humans would respond to regular nightly fasting, Marinac and her colleagues reviewed outcomes of breast cancer survivors from the Women's Healthy Eating and Living Study, which included 2,413 women.
The participants in the study filled out multiple 24-hour dietary recalls, which were collected at baseline, year one, and year four. Pathological characteristics of the original breast cancer diagnosis were abstracted from medical records. Demographic variables and sleep duration were self-reported. Height and weight were collected at the baseline visit. HbA1c and C-reactive protein levels were ascertained from the baseline blood specimen.
The researchers focused on additional breast cancer events over 7.3 years of follow-up and death from breast cancer or any other cause over 11.4 years of Social Security Death Index surveillance.
Marinac said that the statistical analysis adjusted the outcome models for age, race/ethnicity, education, comorbidity, menopausal status, breast cancer stage, breast cancer grade, anti-estrogen use, total calories, evening calories, eating frequency, the study site, and the intervention group. The researchers used multivariate linear regression models to investigate the relationship between nightly fasting and possible mechanisms by which night fasting may influence cancer prognosis.
The study intrigued Dustan Osborn, MD, PhD, a private practice oncologist in Olympia, Washington, asked for his perspective. “The researchers make cogent arguments that fasting could impact breast cancer recurrence. It's a very interesting concept.
“These are the kinds of things that we as clinicians talk to our patients about all the time. We talk about exercise, we talk about calories, and all this stuff. These are things that you can do without spending a lot of money.”
He referenced the Women's Health Initiative, which showed that an intervention with diet and exercise was beneficial. “You don't need to be a physician to be able to grasp this concept. All those people in Florida who have those early bird dinners may be doing the right thing. It's eating on Eastern Time while living on the West Coast.”