Kogevinas M, Espinosa A, Castelló A, et al. Effect of mistimed eating patterns on breast and prostate cancer risk (MCC-Spain Study) [published online ahead of print July 17, 2018]. Int J Cancer. https://onlinelibrary.wiley.com/doi/epdf/10.1002/ijc.31649.
Population-based case-control study
Data came from MCC-Spain, a population-based multicase-control (MCC) study conducted in 12 regions of Spain from 2008 to 2013. The larger MCC study includes cases from 5 tumor types and population controls. This subanalysis included data from men and women aged 20 to 85 with histologically confirmed cases of breast (1,738 women) and prostate (1,112 men) cancer. After excluding individuals who had ever worked night shifts, the final analysis included 621 cases of prostate cancer and 1,205 cases of breast cancer. Population controls included 872 men and 1,321 women who were randomly selected from primary health centers and frequency-matched by sex, geographical area, and age.
Study Parameters Assessed
Participants were interviewed on timing of meals, sleep, and chronotype and completed a Food Frequency Questionnaire.
Incidence of prostate or breast cancer
Compared with participants who went to sleep immediately or shortly after supper, participants who delayed going to sleep for 2 or more hours after supper had a 20% reduction in risk for breast and prostate cancer combined (adjusted odds ratio [OR]: 0.80; 95% confidence interval [CI]: 0.67-0.96) and in each cancer individually (prostate cancer OR: 0.74; 95% CI: 0.55-0.99 and breast cancer OR: 0.84; 95% CI: 0.67-1.06). A similar association was observed in participants who ate supper before 9 pm compared with those who ate their evening meal after 10 pm.
The effect of a longer supper-to-sleep interval was more pronounced among those who adhered to other cancer prevention recommendations (OR [both cancers]: 0.65; 95% CI: 0.44-0.97) and in morning types (OR [both cancers]: 0.66; 95% CI: 0.49-0.90). Those who had both an earlier supper (before 9 pm) and a longer interval between supper and sleep (≥2 hours) had an approximately 25% decreased combined cancer risk (OR: 0.76; 95% CI: 0.57-1.0) compared with those who had supper after 10 pm and a short supper-sleep interval (<2 hours).
In summary, adherence to diurnal eating patterns and, specifically, a long interval between last meal and sleep, were associated with a lower cancer risk.
In 2007 the International Agency for Research on Cancer (IARC) issued a statement that shift work that disrupts circadian rhythms is probably carcinogenic to humans.1
Moreover, experimental and epidemiological data have associated chronic circadian disruption with a number of other chronic diseases, including diabetes, obesity, cardiovascular disease, and others.2-4
If we ask our patients about their bedtime habits and find they are going to bed too soon after dinner, encouraging them to change this habit might lower their cancer risk.
Clearly there is something about sleep patterns that affects health. A June 2018 paper studied the effects of eating meals out of sync to the internal circadian clock on plasma protein levels over the course of a day. Of 1,129 proteins analyzed, about half (573) fluctuated in abundance during a 24-hour circadian cycle. The authors concluded that circadian misalignment altered the biological pathways of 127 proteins, pathways that were related to immune function, metabolism, and cancer.5 The current study under review suggests timing of meals relative to sleep initiation may also have an effect.
Most studies on nutrition and cancer have focused on the types of food consumed, either macromolecules or specific foods containing certain phytonutrients, rather than meal timing. Still, a small number of studies have examined eating patterns. For example, a 2016 study by Marinac et al (reviewed in this journal) found that longer nighttime fasting is associated with lower risk of breast cancer recurrence.6,7
This current study adds several new ideas to our understanding of the relationships between meal timing, sleep, and cancer that could have clinical relevance.
First, going to sleep immediately after eating the evening meal was associated with an increased incidence of breast or prostate cancer. Delaying sleep just 2 hours lowered the combined risk of these cancers by 26% for prostate cancer and 16% for breast cancer. If we ask our patients about their bedtime habits and find they are going to bed too soon after dinner, encouraging them to change this habit might lower their cancer risk. They could choose to either eat dinner earlier or go to bed later. Given results from Marinac et al, an earlier dinner might be more advantageous.
Second, eating the evening meal early also lowered cancer risk. We must remember that these data are from Spain, where the cultural norm is to delay the evening meal to relatively late at night by American standards. In this study, eating supper before 9 pm was associated with an approximately 35% lower risk of cancer compared to eating after 10 pm. How this translates to people in the United States, who generally eat supper around 6 pm, is unclear.
Combining both practices by eating early and delaying going to sleep for a few hours after eating may be the best idea.
Third, the impact of meal timing varied by certain general characteristics. The data were further analyzed by the person’s chronotype, a concept that is recently getting attention. The study's authors describe chronotype as “a human attribute with genetic basis that correlates with diurnal preference for activities in the morning or evening.”8
In simpler words, the chronotype indicates whether an individual is better described as a “night owl” or an “early bird.” The protective benefits of meal times and sleep patterns was greater for chronotypes who favored morning activity; morning types had a 34% reduction of cancer risk compared to only a 14% reduction in the night types. Meal and sleep timing made a larger difference in early birds than in night owls.
This study supports a number of traditional naturopathic concepts, in particular, eating early. It also suggests that simple interventions and changes in lifestyle may have significant impact on cancer risk.