#79 What Is the Best Time to Eat - Circadian Rhythms with Greg Potter PhD

Siim Land (0:00)

So, welcome back. My name is Siim, and I'm here at the Biohacker Summit Toronto with Greg Potter.

Yeah. And your speech was about chronobiology and the circadian rhythms, and especially like, what is the best time to eat food? So, can you like give a brief overview about what we're talking about?

Greg Potter (0:23)

Yeah. I think that historically, most people have been interested in importance of what you eat, as opposed to when you eat. And the main ideas underlying chrononutrition as a science, is that the time of your body's clock influences what it ends up doing with the foods and drinks that you eat, but also the foods and drinks that you eat influence your body's clocks.

And that has very important consequences for your health. So people are now trying to understand, okay, with that in mind, how can I optimize the timing of my diet and the composition of my diet, such that my body's clock functions well and as a result, my health is improved.

Siim Land (1:03)

Yeah, for like the circadian rhythms themselves are this very new thing.

Like the body has these different inner biological clocks and they're constantly being influenced by light and food and temperature and such. How big of a role does nutrition and calories play in this like the circadian rhythms? How do how much influence does it have like compared to light?

Greg Potter (1:27)

Sure, yeah, it depends on the tissues that you're looking at. So we have a master clock in our brains and the timing of that master clock is primarily set by light. So as I mentioned in my talk then, light enters the eyes and then it's detected by these specialized cells called intrinsically photosensitive retinal ganglion cells and then they then relay information about light exposure down the optic nerves and the master clock sits above where these cross and it just samples that information so over time it accumulates your light exposure history and then it knows what is happening outside during the day and then this master clock sends signals elsewhere in your body using a variety of mechanisms so things like signals in nerves, bloodstream and so on to tell clocks elsewhere in your body what the time of day is but every cell in your body has its own clocks and these determine when the cells do things like build structures and break down structures because those two things can't happen at the same time and what's interesting is that whereas the time of the master clock is mostly set by light exposure, the time of clocks elsewhere in your body so the clocks in your liver and your fat tissue and your skeletal muscle for So, the skeletal muscle, for example, is mostly set by food intake. So, what you can do is, you can change the time of your food intake without changing your light-dark exposure, such that it's only the timing of clocks elsewhere in your body that shifts.

And anyway, that's important because it determines when they're optimized for various processes. So, the key principle is that, whereas the timing of your master clock is mostly set by light and dark, the timing of clocks elsewhere seems to be mostly set by your diet. And that's probably important to your health.

Siim Land (3:22)

Okay, yeah. So, what is the best time to eat, so to say?

Greg Potter (3:26)

Yeah. I think, in practice, it depends on the person, what you're optimizing for, when you're physically active and so on. So, what I spoke about in that talk is the fact that you can get some idea of somebody's biological nighttime by looking at their melatonin profiles. So, during darkness, the master clock detects that light is no longer coming in, and then it relays that signal back to the pineal gland in the brain. And this then synthesizes melatonin. Melatonin then circulates in the bloodstream and acts on various receptors and tissues to tell them it's the nighttime, and so to do their nighttime activities.

So, melatonin tie is the biological nighttime.

Because they're doing their nighttime activities, historically, we didn't have access to food at night. So, those don't really involve doing things that are related to digesting food, for example. So, we're not well set for food intake at that time. So, as a starting point, minimizing food intake and digestive processes during the biological nighttime is a good starting point. And as a heuristic, I think that it's useful to minimize food intake for about half an hour after you naturally wake up. So, let's say that you wake up at 6 a.m. to an alarm, but you naturally get up at about 7 a.m. I wouldn't recommend that you eat until at least 7.30, based on that. And then, in general, you see a sharp spike in melatonin synthesis about two hours before bedtime. So, let's say that somebody naturally falls asleep at 10 p.m.