Breast cancer recurrence reduced by prolonged nightly fasting

Breast cancer risk and prognosis is affected by glucose and insulin regulation. The authors of a study recently published in JAMA Oncology demonstrate that fasting intermittently by extending the overnight fast between dinner the night before and eating the next day reduces the risk of cancer recurrence. They state:

"To our knowledge, no studies in humans have examined nightly fasting duration and cancer outcomes."

So they set out to...

"...investigate whether duration of nightly fasting predicted recurrence and mortality among women with early-stage breast cancer and, if so, whether it was associated with risk factors for poor outcomes, including glucoregulation (hemoglobin A1c), chronic inflammation (C-reactive protein), obesity, and sleep."

Breast cancer and HgbA1c reduced by prolonged nightly fasting; sleep improved

They analyzed data collected over 12 years for 2413 women with breast cancer but without diabetes aged 27 to 70 years at diagnosis who were participants in the Women’s Healthy Eating and Living study. Their main outcomes were recurrence, new primary tumors, mortality, assess concentrations of hemoglobin A1c and C-reactive protein. Happily their data show significant improvements in recurrence, HgbA1c and sleep duration:

"The cohort of 2413 women reported a mean (SD) fasting duration of 12.5 (1.7) hours per night. In repeated-measures Cox proportional hazards regression models, fasting less than 13 hours per night (lower 2 tertiles of nightly fasting distribution) was associated with an increase in the risk of breast cancer recurrence compared with fasting 13 or more hours per night (hazard ratio, 1.36). Nightly fasting less than 13 hours was not associated with a statistically significant higher risk of breast cancer mortality or a statistically significant higher risk of all-cause mortality. In multivariable linear regression models, each 2-hour increase in the nightly fasting duration was associated with significantly lower hemoglobin A1c levels and a longer duration of nighttime sleep."

Intermittent fasting

The two most main methods of intermittent fasting are 5:2 and 16:8. 5:2 is 5 days of normal eating alternating with two very low calorie days (500 cal for females and 600 cal for males). 16:8, which I prefer, delays eating and drinking anything other than water, coffee or tea (black) until 16 hours after dinner the night before. This has numerous metabolic and immune benefits, and should be a mainstay in the 'oncology toolbox.' The authors conclude:

"Prolonging the length of the nightly fasting interval may be a simple, nonpharmacologic strategy for reducing the risk of breast cancer recurrence. Improvements in glucoregulation and sleep may be mechanisms linking nightly fasting with breast cancer prognosis."