Breast cancer, nightly fasting

Nightly Fasting Improves Cancer Prognosis

Jacob Schor ND, FABNO

When it comes to diet and cancer, we’ve added a new idea into our practice. Patients are encouraged to extend the gap between eating dinner and breakfast. This idea comes from a pair of studies by Catherine Marinac and colleagues at the University of California in San Diego.

Ample evidence has been published that suggest a solid association between caloric restriction and increased longevity and decreased cancer mortality. While this sounds good in theory, getting patients to adopt a caloric restricted lifestyle is in most cases challenging. The technique investigated by Marinac is relatively easy to adopt; it only requires a few tweaks in meal times.

The most recent of these papers was published March 31, 2016, in JAMA Oncology while the first was published in August 2015. Both papers look at the effect duration of nightly fasting, (those are fancy words for how long you go without eating between dinner and breakfast) on breast cancer risk.

The 2015 study analyzed data from 2,212 women gathered through the US National Health and Nutrition Examination Survey (NHANES).¹ Longer fasting was associated with lower average blood sugar as calculated via A1c levels. Elevated blood sugar is a risk factor for breast cancer recurrence. While this first paper was interesting, the 2016 paper is fascinating.

In the newer study, data from 2413 women who were part of the Women’s Healthy Eating and Living Study (WHEL) were analyzed seeking correlation between poor breast cancer outcome and fasting duration.² Marinac et al report that fasting for less than 13 hours per night was associated with an increase in breast cancer recurrence compared to fasting more than 13 hours per night. Data from women with shorter fasting periods trended toward increased breast cancer mortality but did not reach statistical significance. Longer nightly fasting was again associated with lower hemoglobin A1c results.

The WHEL women fasted for a mean duration of 12.5 hours per night. Fasting less than 13 hours per night was associated with a 36% increase in the risk of breast cancer recurrence compared with fasting 13 or more hours per night. Nightly fasting for less than 13 hours was associated with a 21% non-significant trend toward higher risk of breast cancer mortality, and a non-significant 22% increase in all-cause mortality. Women, who fasted an average of 12.5 hours, had a 36% higher risk of breast cancer recurrence than those who fasted 13 hours per night.² Each two-hour increase in the nightly fasting duration was associated with significantly lower hemoglobin A1c levels and a longer duration of nighttime sleep

The authors write, “Prolonging the length of the nightly fasting interval may be a simple, non-pharmacologic strategy for reducing the risk of breast cancer recurrence. Improvements in sugar regulation and sleep may be mechanisms linking nightly fasting with breast cancer prognosis.”

This is a simple lifestyle change that may improve health. Still, some patients will make it feel like we are negotiating a business deal with them. Anytime we ask them to change their life, they find excuses to resist. Thus, over time, the easier the change is for patients to do, the more attractive it becomes to the practitioner.

These Marinac studies suggest an easier approach will obtain similar benefit as fasting or periods of caloric restriction. Simply prolonging the period of time in which women abstain from food at night, the fasting period between dinner and breakfast, is adequate to achieve significant benefit.

Patients generally resist and for the most part want to avoid anything that requires effort or sacrifice. On the effort scale, increasing duration of nightly fasts by half an hour is flat out easy, especially if one starts out by talking about extreme caloric restriction or fasting and then offer this Marinac scheme as another option.

All we need to do is ask a few simple questions and help patients do the math. “What time to do you finish supper?” “What time do you eat breakfast?” “Can you eat a little earlier in the evening or later in the morning?” This is easy.

I qualify what I wrote above, suggesting that most people are resistant to extended fasting or caloric restriction. There are some exceptions, some people are willing and eager to do and try anything. They have what I think of as a genetic tendency toward sacrifice. In their minds any sacrifice, any voluntarily encountered discomfort or hardship, earns them a reward from the universe, and in this equation, better health. I think this is the same tendency that once led people to line up at sacrificial altars; the same impulse now inspires them to limit their diet and seek out food restrictions and accept that idea that various unappealing foods are in fact beneficial if consumed. But I digress.

These two Marinac papers appear to be the first human studies that have sought a direct association between nightly fasting and breast cancer outcome. In animals, caloric restriction is an effective way to reduce cancer risk.³ Intermittent caloric restriction prevents breast cancer development as well or even better than chronic caloric restriction in animals.⁴ There is only one study that has examined whether meal timing has an effect on tumor progression in mice. Mice whose feeding times were restricted had smaller tumors than mice fed as much as they wanted.⁵ Feeding mice during the light phase of their day was associated with less tumor growth. How do we translate that? Mice are nocturnal. Would this be equivalent to feeding people late at night or waking people during sleep to eat? Probably not; mice experiments only go so far in duplicating human biology.

In both groups of women in the Marinac studies, members of either the NHANES or WHEL study cohorts, longer nightly fasting was associated with a lower hemoglobin A1c levels. Giovanucci et al, also having analyzed data from NHANES, reported a similar finding in 2010.⁶ Longer fasting is associated with lower blood sugar, a measure that may limit growth of breast cancer cells. Erickson et al reported in 2011, in a separate analysis of data from the WHEL cohort, that women with a A1c > 7.0%, were more than twice as likely to die during the study than women with an A1c less than 6.5%.⁷

In an August 2015 analysis of NHANES data, Marinac et al reported that among 2019 women, longer night time fasting was associated with significantly lower c-reactive protein levels, but only in women who ate less than 30% of their daily calories after 5 PM.¹ So we might modify our diet instructions and suggest eating bigger lunches and smaller suppers. This is starting to sound like things we learned back in naturopathic school.

In the 2016 paper, longer nightly fasting was not associated with basal metabolic index (BMI). Longer fasting was however associated with longer sleep duration. Late night eating disrupts circadian rhythms. Eva Schernhammer’s multiple studies looking at night-shift workers have produced convincing evidence that circadian misalignment is linked with increased cancer risk, including increased risk of breast cancer.⁸

While these new findings are the result of retrospective analysis of data gathered two decades ago, the results are intriguing. As always, there will be those who suggest waiting for more definitive data gathered from a large prospective randomized trial before bringing this practice into clinical use. This writer is not among that group as, at this point, there is no evidence that longer night-time fasting is associated with any increase in risk. At the worst, this idea may prove to be ineffective. Given that this study suggests a nearly 40% shift in cancer recurrence rates, longer night time fasts may have clinically significant value.

Obviously, we cannot yet know whether the association revealed by this data is causal or not. It could be that women who produce higher amounts of insulin choose to forgo long night time fasts for the simple reason that they become hypoglycemic easily if they wait too long to eat. In simpler words, they wake up hungry and don’t hold off breakfast. Eating patterns may simply select for differing levels of insulin production. Length of night-time fasts may simply be a biomarker of insulin production and not serve as an intervention. Still, what’s it going to hurt to try?

In fact, what would it hurt to try this night-time fasting routine in people at risk for other types of cancer recurrence? No good reasons not to try it come to mind.

Up until now, we have had a number of unappealing choices on the menu for patients seeking the benefits of caloric restriction. There are the three-to-four-day 500 calorie diets Valter Longo has experimented with. There are the alternate-day-caloric restricted diets that switch from regular food intake to significantly restricted calorie intake every other day. Then there is the once-a-week fasting or low-calorie day approach. While patients may brave one of these diets, the practice is often of short duration; basically, few people love the experience and quickly find an excuse to discontinue. These night-time ‘fasts’ are different; patients see them as simply having a late breakfast. There is something leisurely, almost pleasant in starting the day a bit later. Rather than hardship, it feels somewhat laidback if not luxurious, a kind of every-day-is-a-holiday feeling. Patients are able to do this day after day and week after week. We do not yet know if they are as effective as other approaches, but we certainly know they are doable.

So, at our clinic, in addition to simple prescriptions for daily exercise, a healthy Mediterranean patterned diet, and adequate sleep, we now tell our breast and other cancer patients to “eat an early dinner and a late breakfast.”

It sounds almost too simple. Often the best of naturopathic medicine is like that. Simple. It feels natural.