Nightly fasting may help reduce breast cancer risk

Fasting during sleep for more than 13 hours a night may offer protection against recurrence of illness among women with early stage breast cancer, say findings published online in JAMA Oncology.
[breast cancer survivors]
When we eat, as well as what we eat, may help prevent recurrence of breast cancer.


Breast cancer is the number one cause of cancer death among women in developing countries and the second most common cause of cancer death in developed countries.


In the US, 224,147 women and 2,125 men received a breast cancer diagnosis in 2012, and 41,150 women and 405 men died from breast cancer.


Much attention has focused on the positive effects of a healthy diet on breast cancer outcomes. However, the results of research into which foods or food groups and which dietary patterns can help have been mixed.


Recently, a new theory suggested that timing also matters, and that when we eat has an impact on metabolic health and cancer.


Previous mouse studies have shown that rodents who consumed a high-fat diet but repeatedly fasted for at least 16 hours experienced protection against abnormal glucose metabolism, inflammation and weight gain. All of these factors have been linked to poor cancer outcomes.


Ruth E. Patterson, PhD, of the University of California-San Diego, and colleagues have been looking at the potential effects of nightly fasting on breast cancer prognosis.

Health benefits of fasting more than 13 hours a night


They looked at data for 2,413 women who were registered in the Women’s Healthy Eating and Living study from 1995-2007. The average age of the women was 52.4 years. All participants had early stage breast cancer and were aged 27-70 years at the time of diagnosis. None of the women had diabetes.


On average, the participants fasted for 12.5 hours each night.


The study focused on the recurrence of invasive breast cancer and new primary breast tumors during an average follow-up time of 7.3 years, in addition to death from breast cancer or any cause over an average 11.4-year period.


Women who fasted for less than 13 hours a night had a 36% higher risk for breast cancer recurrence, compared with those who fasted for 13 or more hours.


No link emerged between shorter fasting time and death from breast cancer or mortality from any other cause.


Patients with early stage breast cancer who fasted for longer had significantly lower concentrations of HbA1c and longer sleep duration.


Since nightly fasting appears to improve glycemic control and sleep, the researchers propose that, as well as having a positive effect on breast cancer outcomes, longer fasting could help to reduce the risk of type 2 diabetes, cardiovascular disease and other cancers.


One limitation of the study is the use of self-reported dietary data.


Nevertheless, the authors note that the findings have important implications for public health.


They say:

“Our study introduces a novel dietary intervention strategy and indicates that prolonging the length of the nightly fasting interval could be a simple and feasible strategy to reduce breast cancer recurrence.”


They call for further studies, including randomized trials, to test the effectiveness of prolonging nightly fasting in reducing the risk of chronic disease.


Medical News Today has previously reported that adhering to a calorie-restricted diet that mimics fasting for a limited period of time may be good for the health.

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