In a new study, researchers found that physical activity can reduce cancer risk, and that morning exercise may have the greatest protective effect.
The research was conducted by a team at the Pompeu Fabra University in Barcelona and elsewhere.
Previous research has shown a possible correlation between factors that disrupt our circadian rhythms, such as exposure to light during the night or eating late in the evening, and the risk of developing cancer.
Furthermore, studies have repeatedly demonstrated that regular moderate physical exercise can significantly reduce cancer risk.
However, so far it has not been clear whether the time of day when physical activity takes place plays any significant role.
In the study, the team examined the hypothesis that sporting activities in the morning potentially reduce the risk of prostate and breast cancer more than sporting activities at other times of the day.
The hypothesis is based on results from an experimental study showing that physical activity in the afternoon or evening can delay the melatonin rhythm.
The human body primarily produces the hormone melatonin during the night and some studies have associated this hormone with lower cancer risk.
The team of scientists tested 2,795 participants in the population-based Multi-Case Control Study (MCC-Spain).
They found that the protective effect of exercise on the risk of developing prostate or breast cancer is potentially greatest when physical activity takes place between 8:00—10:00 in the morning.
However, in men, this effect was just as strong for regular sporting activity in the evening (19:00—23:00 hrs.)
The participants’ chronotypes, that is to say, their preferences for sleep and activity at a particular time of day likewise influenced the results: morning exercise (8:00—10:00) appeared to be particularly good for participants who essentially prefer to be active in the evening—so-called “owls” or late chronotypes.
The team says the timing of physical activity obviously has an effect upon the rhythm of sex hormones and melatonin, as well as on food metabolism. That might explain the results.
One author of the study is Jakob Weitzer.
The study is published in the International Journal of Cancer.
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