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Turning in for the night right after a big meal may lead to more than heartburn. A study published in the International Journal of Cancer suggests that the later you eat dinner, the more likely you are to develop two of the most common cancers.

Researchers at the Barcelona Institute for Global Health in Spain were curious about the potential cancer impact of disrupting our internal clock, or circadian rhythm. It helps the body regulate everything from sleep and energy levels to hormones and body temperature throughout out the 24-hour cycle of a day. Light is a major disruptor of these rhythms, as is the timing of when you usually eat.

It’s known that breast and prostate cancers are the two malignancies most closely associated with night shift work that disrupts circadian rhythms. So the Spanish researchers surveyed more than 1,800 breast and prostate cancer patients, along with some 2,100 healthy men and women, none of whom worked night shifts. They were asked about their dining habits; specifically, how long after the last meal of the day did they wait to go to bed. After adjusting for things like family cancer history and socioeconomic status, the results showed that individuals who eat dinner before 9:00 pm or wait at least two hours after finishing to retire have about a 26 percent lower risk of developing prostate cancer and a 16 percent lower risk for breast cancer, compared to those who eat after 10 or go to bed shortly after their final meal of the day.

What’s at work here?

Dr. Brian Gonzalez, researcher in Moffitt's Health Outcomes and Behavior Program

Moffitt researcher Dr. Brian Gonzalez studies circadian rhythms as part of his efforts to improve quality of life issues for cancer patients and survivors. He says recent research suggests that disrupting one’s circadian rhythm can impair your body’s ability to fight off disease – including cancer.

We each have our own internal clock, but Dr. Gonzalez says the timing isn’t set in stone. “It can be adjusted using various cues such as sleeping and light exposure. For example, when you travel from one coast of the United States to the other, your body adjusts to the new schedule in part because you’re sleeping and exposed to light on a different schedule. This happens over the course of a few days, and during the transition we experience ‘jet lag’ when our circadian rhythms aren't in sync with the new time zone.”

Unfortunately, we can also cause “jet lag” without even leaving town. Adhering to one sleep schedule during the work week and a radically different schedule during the weekend can cause our bodies to constantly be adjusting every weekend and every work week. Timing of meals can also affect your circadian rhythm, as eating food is another cue that tells your body it’s daytime. Eating at times that would otherwise be considered “nighttime” by your biological can cause circadian disruption.

So, should you move up your mealtime? The Spanish researchers admit more study is needed to understand the mechanisms that might relate late mealtimes to the onset of cancer – this study only shows correlation, not causation.

But they say individuals in the study who waited even longer between mealtime and bedtime were also more likely to adhere to established cancer prevention guidelines.

Early diners might simply be more attuned to living healthier – and maybe we’d benefit by following their example.