The Role of Meal Timings in the Circadian System and the Association with Cancer Risk

Circadian rhythms, from Latin “around a day”, are cycles of 24 hours that allow the anticipation and adaptation of the body to daily external changes and which are coordinated by the circadian clock. In humans the circadian clock is responsible for regulating multiple activities including sleep, movement, body temperature, hormonal secretion, immune regulation, and the cell cycle.

This system is regulated by a central clock located in the brain and multiple peripheral clocks located in other tissues. The light/dark cycle captured by the eyes is in charge of synchronizing the central clock, but meal timings play a key role in resetting peripheral clocks in the muscle, liver, pancreas and the adipose tissue.

 Regulation of the circadian system by light exposure and meal timing.

Flanagan A, Bechtold DA, Pot GK, Johnston JD. Chrono-nutrition: From molecular and neuronal mechanisms to human epidemiology and  timed feeding patterns. J Neurochem. England; 2021;157:53–72.

Chronodisruption is the alteration of circadian rhythms resulting from a misalignment of the internal clock with mistimed external inputs. Given the broad implication of the circadian clock in biological processes, it is intuitive to think that chronodisruption can have negative consequences for human health. It has been suggested that disruption of the circadian rhythm can lead to cellular transformation, proliferation and tumorigenesis. The International Agency for Research on Cancer (IARC) classified shift work involving circadian disruption as probably carcinogenic to humans for cancers of the breast, prostate and colon.

It has been suggested that disruption of the circadian rhythm can lead to cellular transformation, proliferation and tumorigenesis

In the past decades, much attention has been given to exposure to artificial light at night as the main source of chronodisruption. The main hypothesis linking exposure to light at night with an increased cancer risk is the decrease in the production of melatonin, the body’s internal signal for darkness and a molecule with anti-cancerogenic potential. However, less is known about the role of meal timings in circadian regulation.

Between 2008 and 2013, the multicase-control MCC-Spain study, coordinated by Manolis Kogevinas and Marina Pollan, was conducted in Spain to evaluate etiological factors for common cancers in Spain. In this population-based study, participants answered a general questionnaire that included information on socio-demographic factors, lifestyle and family medical history. A circadian questionnaire was also answered by the participants including questions on meal timings, work shifts and sleep patterns.

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In 2018, a paper published by Manolis Kogevinas and colleagues showed that having an early supper and a longer time interval between supper and sleep was associated with a reduced risk of having prostate and breast cancer.

In 2018, a paper published by Manolis Kogevinas and colleagues showed that having an early supper and a longer time interval between supper and sleep was associated with a reduced risk of having prostate and breast cancer

Following the popularisation of prolonged nighttime fasting regimens and some publications suggesting a protective association with metabolic health, we examined the association of nighttime fasting duration and prostate cancer risk. In this paper, recently published in the journal Nutrients, we considered whether the time window of this period of fasting (breaking the fast early in the morning versus prolonging it by skipping or delaying breakfast) played an important role in this association.

We analysed data from 607 prostate cancer cases and 848 population controls from the MCC study. We calculated nighttime fasting as the period of time between the last eating episode (considering any after supper snack) and breakfast the following day. For people that reported not having breakfast, we considered lunch as the broader concept of the time when the nightly fast was broken.

Our results showed that fasting for more than 11 hours overnight (the median duration among controls) was associated with a slight reduction in the risk of prostate cancer, specifically by an 8%. After adjusting for time of breakfast this association was strengthened and the risk was reduced by a 23% showing that the time of breakfast was an important factor in this association. Indeed, in a model combining both nighttime fasting duration and time of breakfast we observed that the nutritional behaviour associated with a lower prostate cancer risk was having a long nighttime fasting and an early breakfast (8.30 am or before). These results, that should be cautiously interpreted, were maintained even after considering factors such as the quality of the diet, the consumption of alcohol or smoking.

Although more studies are needed to confirm this association, these results indicate that having a long nighttime fasting period could be associated with a lower risk of prostate cancer when this period of fast is broken early in the day

In addition to the previous results from the MCC study in relation to time of supper and interval of time between supper and sleep, these findings show the importance of aligning meal timings with circadian rhythms. Although more studies are needed to confirm this association, these results indicate that having a long nighttime fasting period could be associated with a lower risk of prostate cancer when this period of fast is broken early in the day. Both investigations highlight the importance of meal timings in the regulation of the circadian system and in cancer research.

More information:

Palomar-Cros A, Espinosa A, Straif K, Pérez-Gómez B, Papantoniou K, Gómez-Acebo I, Molina-Barceló A, Olmedo-Requena R, Alguacil J, Fernández-Tardón G, Casabonne D, Aragonés N, Castaño-Vinyals G, Pollán M, Romaguera D, Kogevinas M. The Association of Nighttime Fasting Duration and Prostate Cancer Risk: Results from the Multicase-Control (MCC) Study in Spain. Nutrients. 2021 Jul 30;13(8):2662. doi: 10.3390/nu13082662. PMID: 34444822; PMCID: PMC8399976.