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Prolonged nightly fasting may reduce breast cancer recurrence risk
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Fasting for fewer than 13 hours per night may increase the risk for disease recurrence in women with early-stage breast cancer, according to an analysis of data from the Women’s Health Eating and Living study.
Although previous studies on nightly fasting duration and clinical outcomes have not been conducted, research suggests fasting regimens can improve breast cancer risk factors related to glucoregulation, inflammation, obesity and sleep.
Ruth E. Patterson
Ruth E. Patterson, PhD, professor in the department of family medicine and public health at University of California, San Diego, and associate director of population sciences and leader of the cancer prevention program at the Moores Cancer Center, and colleagues used data from the Women’s Health Eating and Living study to evaluate whether nightly fasting duration was associated with breast cancer recurrence and mortality.
The Women’s Health Eating and Living study — conducted between 1995 and 2007 — included women who recently had early-stage breast cancer. Researchers of that trial sought to assess whether a diet rich in vegetables, fruit and fiber and low in fat would improve breast cancer outcomes; however, the dietary intervention did not improve breast cancer prognosis after a median of 7.3 years of follow-up.
Patterson and colleagues evaluated data from 2,413 women (mean age, 52.4 years; mean BMI, 27) enrolled in this study. All women had breast cancer but did not have diabetes, and they had time-stamped, 24-hour dietary recall data and complete data on key confounders. A majority of women were white (85.5%) and college educated (55.3%).
The mean nightly fasting duration in the cohort was 12.5 hours, and women had a mean of 4.4 eating episodes daily. Overall, 1,595 of the women reported a nightly fasting duration that was shorter than 13 hours, whereas 818 of the women fasted for 13 hours or longer.
Women with a nightly fasting duration shorter than 13 hours were more likely to be college educated (57.6% vs. 50.9%; P .001), had a lower mean BMI (26.7 vs. 27.5; P .01), slept for fewer hours each night (fewer than 6 hours; 6.8% vs. 4.9%; P .001), ate more calories daily (mean, 1,769 vs. 1,644; P .001) and were more likely to eat after 8 p.m. (45.1% vs. 8.4%; P .001).
Results of repeated-measures Cox proportional hazards regression models showed fasting fewer than 13 hours nightly increased risk for breast cancer recurrence 36% compared with fasting 13 hours or more nightly (HR = 1.36; 95% CI, 1.05-1.76).
However, shorter nightly fasting did not increase risk for breast cancer-specific mortality (HR = 1.21; 95% CI, 0.91-1.6) or all-cause mortality (HR = 1.22; 95% CI, 0.95-1.56).
Each 2-hour increase in nightly fasting duration was associated with a 0.37-mmol/mol lower glycated hemoglobin level (beta = –0.37; 95% CI, –0.72 to –0.01) and more hours of sleep per night (beta = 0.2; 95% CI, 0.14-0.26).
“Given the associations of nightly fasting with glycemic control and sleep, we hypothesize that interventions to prolong the nightly fasting interval could potentially reduce the risk for type 2 diabetes, cardiovascular disease and other cancers,” Patterson and colleagues wrote. “Thus, findings from this study have broad and significant implications for public health.”
Additional trials are needed to further assess this association, according to the researchers.
“If future trials confirm that habitual prolonged nightly fasting improves metabolic health, this would be an important discovery in prevention that could reduce the risk for cancers, type 2 diabetes and cardiovascular disease,” Patterson said in a press release. – by Alexandra Todak
Disclosure : The researchers report no relevant financial disclosures.
Perspective
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Douglas Yee, MD
The Women’s Healthy Eating and Living (WHEL) study was a randomized clinical trial using an intervention to increase portions of fresh fruits and vegetables to five servings per day. The intervention patient group received telephone counseling, whereas the control group received only print material. The intervention was successful in improving fruit and vegetable intake but was not successful in affecting breast cancer mortality.
Previous published post-trial analyses showed that women most active at baseline or maintained high fruit/vegetable intake and moderate levels of physical activity resulted in improved breast cancer outcomes.
In addition, the WHEL investigators provided another look at the same patients and found nightly fasting for more than 13 hours also was beneficial. The subset of women (mostly white and college educated) who fasted fewer than 13 hours per night had a higher risk for breast cancer recurrence, but no differences in breast cancer or overall mortality. Several additional exploratory studies were performed and showed women with longer fasting intervals had lower hemoglobin A1C levels and a longer duration of sleep. BMI and inflammation — as measured by C-reactive protein — were not different between the short and long nightly fasters. This type of subset analysis cannot provide a mechanism, but it is notable improved glycemic control and sleep hygiene are both associated with improved health outcomes.
So how can we use this information when we talk to our patients? On one hand, it reinforces the idea that healthier women, or those with more physical activity, less metabolic syndrome and better sleep patterns, have better breast cancer outcomes. It would be nice to believe that if we could discourage women from eating late at night (no nightly bowl of ice cream?), we could reduce breast cancer mortality as effectively as we do with current adjuvant endocrine therapies. However, this type of subset analysis is hypothesis generating at best and does not prove cause-and-effect of the benefits of nightly fasting.
On the other hand, these findings help us with the question almost every oncologists gets from their patients: “What can I do to help reduce my risk?” Nightly fasting for more than 13 hours seems an intervention with low risk of harm and is yet another piece of data-backed advice — along with reduced caloric content from fat and increased physical activity — we can use with our patients as we encourage a healthy lifestyle.
References:
Bertram LA, et al. Cancer Causes Control. 2011;doi: 10.1007/s10552-010-9714-3.
Pierce JP, et al. JAMA. 2007;298:289-298.
Pierce JP, et al. J Clin Oncol. 2007;doi:10.1200/JCO.2006.08.6819.
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