Sleep is kind of like the ocean. Hear me out. We know the ocean is vast, but we also realize there is so much we have yet to discover about all that water. Well, we know sleep is a big part of our day, and we're still very much researching unknowns about our slumber. What we do know, thanks to health organizations like the National Heart, Lung, and Blood Institute, sleep has important effects on our heart and circulatory systems, memory, metabolism and our respiratory and immune systems.
We're talking about sleep this week for our series Balance, which is about health, exercise and nutrition. We again asked Jamie Baum and Erin Howie to the Anthony and Susan Hui News Studio for this conversation. Jamie is associate professor in the University of Arkansas Department of Food Science and director of the Center for Human Nutrition at the University of Arkansas. Erin Howie is associate professor of exercise science at the UofA.
Jamie says much like sleep is connected to much of our health, our behaviors can be very much connected to our sleep.
Baum: For sure, diet and nutrition play a role, if not directly, indirectly through diet-related chronic diseases. So things like type 2 diabetes or obesity or overweight can impact our sleep quality in a negative way. So it is linked to diet. There's a lot of research going on right now about nutrient quality or diet quality and sleep, because I think people are starting to recognize that sleep is really important and a risk factor for a lot of things like depression or quality of life. And there's a lot of talk about sleep with exercise, kind of a chicken-or-the-egg type problem. So do you sleep better because you did exercise in the afternoon, or because you got a good night's sleep, do you have more energy to exercise the next day?
But there's been a movement globally called 24-hour movement guidelines, or thinking about 24-hour movement patterns. And this idea that you only have 24 hours in the day and you fill them with something. So either you're sitting or you're moving. So you're doing physical activity or exercise, or you're sleeping. And those are kind of your three options. So if you sleep more, you have to decrease how much you're sitting or how much you're doing activity. And so they kind of all affect each other.
And Canada was the first country to adapt these at the national level. So they have 24-hour movement guidelines for kids and adults. Australia has had them for a while for kids. And just a month or two ago they adopted them officially for adults. So now their national activity guidelines include sleep, because they recognize that it's really important for a variety of health outcomes from mental health, cardiometabolic health, cancer. Basically anything, you name it.
Kellams: So do they give values, like a range for what they would consider good sleep?
Baum: Yeah. Their recommendation is seven to nine hours for adults. And there's a lot of individual variability in sleep needs. So that's why there's kind of that range.
Kellams: Do they break it down into percentages? I understand that REM sleep is really good, you need a certain amount of that, you need a certain amount of other sleep, you need continuous sleep.
Baum: They haven't gotten that far.
Kellams: When they talk about seven to nine hours, I'm assuming it's like in a single stretch, versus maybe you sleep five hours but you take a siesta for two hours in the afternoon?
Baum: Yeah, there's a lot of questions about how you accumulate sleep and the research evidence isn't out there to support the really specifics. The one thing that we do know are overnight shifts. So working at night is really bad for your health. So when you sleep in the daytime and you're up at night, that's not very good for you. And you have to take additional behavioral measures to try and combat that. Even nutritionally, shift workers tend to struggle with chronic diseases, poor nutrition choices and a lot of negative behaviors from just shifting their circadian rhythm to what we would expect — to be awake during day hours, not night.
And there's probably a difference too, at the individual level, about when you sleep. So there's a lot of talk now about chronotypes. It comes from your genetics. You're predisposed to what chronotype you have, but you think of it as like a morning person or a night owl.
Kellams: What are you, Kyle?
Kellams: Oh, I'm definitely a morning person.
Baum: Me too. But I'm married to and raising night owls, and so that can be a bit of a conflict in a household. Especially if you're sharing a room or a bed. I mean, one person wants to go to bed at 9, the other one's getting in the covers at 2:30 or 3.
Kellams: Well, that's why you need noise-canceling headphones and someone that sleeps like a log next to you. Going back to what we put in our bodies and sleep — we all know that caffeine is an accelerant. Are there other things that we think can help us sleep better, if we have a more balanced diet?
Baum: Well, every episode, it's kind of funny that we come back to balance, because people who have healthier lifestyle behaviors, like regular physical activity, proper fruit and vegetable intake, tend to have overall better health and better sleep quality.
But we have been — we're closing in on the end of our second dietary intervention with postmenopausal women, looking at increased protein intake. So a target of around 25 to 30 grams of protein per meal, and how that impacts sleep quality. So one of the cool things we do is actually — it started with the help of Erin's lab — wearing these, it's called wrist actigraphy. They're monitors and we can track sleep. Participants wear them for seven days and also keep a diary of "I got in bed at this time, I woke up at this
time," and it can tell us: did you actually sleep? What was your sleep like? Did you get up during the night?
So the women who are on this higher protein intake — their sleep does not improve physically or physiologically, but they're reporting that they feel more rested, more energetic and ready to face the day. And we've seen that in two studies. And I was talking to someone who does protein research in adolescents and sleep, and her adolescents are reporting the same thing. In reality, they're not sleeping better, but they're feeling like they're sleeping better. If you're feeling like you can go conquer the day in a better way, there's something to be said for that.
Kellams: What about a connection between exercise, regular exercise and sleep? I know that when I was training for marathons, I was more tired by the time it was what I considered time to go to bed, 9:30 or 10, and it felt like I slept more. That's the thing about sleep — it's kind of anecdotal even for yourself, because you're asleep when it's happening. How much do we know about the connection between exercise and good sleep?
Howie: Like I said before, we kind of know that they are related, but we're not sure which causes which. And kind of like Jamie was saying, there's a lot of things that go into sleep from the amount you get, but also all these physiological responses. So things like your metabolism and how it changes when you sleep versus when you're awake, your core body temperature changes. And those are things that also change with exercise.
One of the questions we get a lot — and a couple years ago it got a lot of press — is when you should exercise. Should you exercise in the morning or at night? And if you exercise at night, does that give you worse sleep? There's been a little bit of research around that. And for most people, it doesn't really matter. You're not going to severely impact your sleep whenever you exercise. There's a little bit of difference between the type of exercise. Really long, vigorous exercise within four hours of bedtime can sometimes impact some of your sleep metrics, but not all of them. So it might affect your sleep quality but not necessarily your sleep quantity.
And that's especially for people who are morning chronotypes. So if you're a morning person and you are going for a 10-mile run at 7 p.m. and trying to go to bed at 9, that's probably going to impact your sleep. If you're a night owl and you're exercising at night before bed, it's probably either not going to affect your sleep or affect it a lot less. So it comes down to the individual person. And in general, physical activity or exercise anytime throughout the day is going to be better for health and better for sleep over the long run.
Kellams: I know we call this Balance, but we could also call this series Cyclical, right? Because everything sort of harmonizes with everything else if you're doing it well.
Howie: I used to be a morning workout person, but now the mornings are the only time I have like an hour to myself a day. So I switch to nighttimes. So on the days I work out, like at 6 p.m. to a scheduled class, I'm probably up to like 10 or 11. But it doesn't impact the fact that I wake up at 5. And a lot of these are their associations between the things. So for a while it was people who exercise in the morning are healthier. And that's probably just because they're more likely to exercise in the morning before their
schedule, and the workday doesn't stretch out for them. It's not because it's the morning, it's just because they get it in.
Kellams: And you can sort of change your chronotype over time?
Howie: Your chronotype can change as you age. So often it shifts more towards being a morning person, but you can't really deliberately change it. So if you're a night owl and you're like, "I'm going to get up at 5 a.m. every morning," you can change your bedtimes and wake times, but that doesn't necessarily influence your overall chronotype.
Age does impact sleep. And especially women, as we are transitioning through perimenopause into menopause, hormonal shifts and things like that can impact sleep quality, but often it tends to return to whatever your normal was once you've gone through that transition. Stress, all kinds of things impact sleep. But once people start — if you address sleep — one thing in the reading I've been doing in the literature is that it can sometimes fix a lot of these problems. Because if you feel more rested, you may have more energy to put more thought into creating balanced meals, putting in time for physical activity and things like that.
And I know it's seasonal as well, because in the winter, once it's dark, I'm not going back out. But just acknowledging the other end of the continuum: there was a big review that showed that physical activity about 150 minutes a week, which is what we talk about in our guidelines, is best for sleep. But if you get much beyond that — so you think of people who are training for long events or have unhealthy relationships with exercise — it actually impairs their sleep. So there is such a thing as too much of a good thing.
Kellams: Sure. And 150 minutes a week — if you do it seven days a week, that's just over 20 minutes a day, which isn't that much. And that's just moderate. If you do vigorous, it's half as much.
Howie: There you go.
Kellams: Thank you both.
Baum: Thank you, Kyle.
Jamie Baum is associate professor in the University of Arkansas Department of Food Science and director of the Center for Human Nutrition at the University of Arkansas. Erin Howie is associate professor of exercise science at the University of Arkansas. Our series Balance is dedicated to conversations about health, exercise and nutrition.
Ozarks at Large transcripts are created on a rush deadline and edited for length and clarity. Copy editors utilize AI tools to review work. KUAF does not publish content created by AI. Please reach out to kuafinfo@uark.edu to report an issue. The audio version is the authoritative record of KUAF programming.
