hey friends, welcome back to the channel. So, I recently turned 30, and I decided that I want to take my health a lot more seriously than I have done in the past. I've been trying to figure out what are genuinely these scientific evidence-based habits that I can add to my life that will help me be healthier. Now in this video, we're going to be talking about three specific health habits. We're going to be talking about should you be getting 10,000 steps a day. We're going to talk about how much sun exposure should you get and should you actually be going out in the sun first thing in the morning. Thirdly, we're going to talk about how much water should you actually be drinking and should you aim for 2 and 1/2 L per day. I was kind of surprised doing the research for this video because it seems like a lot of the recommendations we yet aren't really that evidence-based. Oh, and by the way, if you're new to the channel, hi, my name is

Ali, I'm a Dr. turned entrepreneur, YouTuber, and author of the book Feel Good Productivity, which is about how to be more productive in a way that feels good. So in this video, I'm excited to dive into some of the scientific research around these three fairly simple but important health habits. So let's get into it. All right, so back in 1964 before the Tokyo Olympic Games, there was a marketing campaign that was used to promote walking 10,000 steps a day. And this number was chosen because the Japanese character for 10,000 looks like a person walking, apparently. And during this campaign, they were promoting this device called the man-poke. And in Japanese, man-poke literally means 10,000 steps meter, which counts the number of steps you've taken. So this number was chosen pretty randomly for the campaign, but it's become mainstream all over the world, and now it's like the number that everyone talks about when it comes to walking. But does the science actually support this? Should we actually be

walking 10,000 steps a day. Now, this is something I've been really keen to find out because 10,000 steps a day is actually quite a lot. And left to my own devices, I only get maybe 4,000 or 5,000 steps a day. So, I've been trying to figure out, should I actually be working more? Is it genuinely good for my health? Now, you might not know this, but 10,000 steps is about 5 miles or 8 kilometers with a little bit of variation depending on the individual. And it roughly takes 1 hour and 40 minutes to walk 10,000 steps. Conveniently, this roughly translates to 10 minutes per 1,000 steps. This was new to me. I had no idea until we were doing research with this video. It's like, oh, for every 1,000 steps you do, you need to walk for about 10 minutes. About 10,000 steps is 100 minutes. And so, should we really be spending 100 minutes every single day just walking to answer that

question. Let's look at what some of the data says. Now, meta-analyses are these big studies that take data from lots of other research papers and bring them together, which is kind of cool. And this meta-analysis from 2022 looked at 15 different studies to see how daily step count was associated with the risk of dying from any cause. And in science, this is what we call all-cause mortality. This graph shows how your risk of death changes with the more steps you take each day. This is what it looks like for people younger than 60, and this is what it looks like for people older than 60. So, if you're younger than 60 years old, which you probably are if you're watching this channel, the optimal number of steps to take is around 8,000 to 10,000. And for people older than 60, you actually lower your risk of death by about 50% by only walking about 6,000 steps per day. Now, because both of these lines are really steep at the start, this

tells us that increasing our daily step count is really good. If you are currently pretty inactive and you don't move around a lot, and then over 10,000 steps per day, you can start to see that the graph sort of starts to level out. But to be honest, this is probably because there's not actually enough studies that specifically look at people who actually do walk over 10,000 steps per day. So the data in this range is a little bit more unreliable, and we don't actually know quite yet if your risk of dying keeps on decreasing if you just take more and more and more steps. Now, this graph is for all-cause mortality, but interestingly, we see exactly the same pattern when it comes to your risk of cancer and dementia and heart disease. In this study, for example, researchers measured the number of steps taken per day by around 880,000 adults in the UK around the age of 61 to see how this changed their risk of getting dementia around 7 years later. And as we can see

Here, the total number of steps per day that showed the greatest reduction in risk of dementia was just under 10,000. This magic number, again, we can see a similar sort of pattern for cancer as in this graph. And again, here you can see around 10,000 is when things start to get interesting. And we also see pretty much an identical pattern when it comes to heart disease. And again, if you zoom into the graph, you see that this 10,000 number shows up again and again. Now, if we look at all-cause mortality again and we separate it out into people who sit for more than 10 hours a day, i.e., me, and people who sit less than 10 hours a day, if you sit a lot, then actually the benefit of walking those 10,000 steps is greater than people that don't sit a lot. And so, what this data shows is that it looks like walking seems to offset the negative health outcomes associated with sitting at a desk all day. Okay, so let's talk about the key takeaways from all

these studies. So firstly, any amount of walking is good for you, and you don't necessarily need to hit 10,000 steps to start seeing the benefits from walking. But in general, the more walking you do, the better. And also, the faster you walk, too, the better. There were some a bunch of studies about this. They were too long to include in this video, but if you walk at a brisk pace, you're more likely to get benefits than if you walk super super slowly. Also, if you walk faster, it takes less time to get in your 10,000 steps. Now, a great target to aim for for most people is around 6 to 8,000 steps per day, because beyond that, the benefits do start to diminish. And if you remember that 1,000 steps is equivalent to about 10 minutes of walking, then this goal actually seems pretty realistic for a lot of us. This would mean that if you walk, for example, 30 minutes total and your commute to get the train or the bus to work, whatever the thing is that would

be 3,000 steps, and then you only really need another half an hour walk, which you can take during a lunch break or any other time, to be hitting that target of 6,000. So what I'm personally taking away from this is that I'm going to aim to start off my day with a half an hour walk around the local park with a little coffee, and that will be my first 3,000 steps. And then I'm also going to try my best to, like, you know, when I have to get to a restaurant that might be half an hour away, aiming to walk there for 3,000 steps rather than getting an Uber or getting the tube. Walking also has a bunch of benefits to creativity, which we're not talking about in this video, but you know, this is why I find whenever I'm kind of feeling blocked on writing or anything I'm working on, actually just going for a walk really helps clear my mind, and it means that I'm more creative, but I also get the steps in, which is

always a good thing. And as of last week, when we did the research for this video, I've decided to add in my daily walk as part of my ideal week. Uh, if you haven't yet come across my ideal week method for managing your time, there will be a completely free template linked down in the video description so you can check that out. It's one of the time management techniques that has most impacted my life. But of course, mental health is just as important as physical help, and one way to improve that is with therapy provided by BetterHelp, who are the paid partner of this video. BetterHelp is the world's largest therapy service, and it's 100% online. With BetterHelp, you can tap into a network of over 30,000 credentialed and experienced therapists who can help you with a wide range of issues. It's a platform that makes finding a therapist easy because it's online and it's remote. And by filling out a few questions, BetterHelp can match you to a credentialed therapist very quickly. Then you can talk to your

therapist. However, you feel comfortable, whether it's via message, chat, phone, or video call. Regardless of whether you have a clinical mental health issue like depression or anxiety, or if you're just a human who lives in this world who's going through a hard time, therapy can give you the tools to approach your life in a very different way. You can message your therapist at any time and schedule live sessions whenever it's convenient for you. And if your therapist isn't the right fit for any reason, you can switch to a new therapist at no additional charge. If any of that sounds good, then BetterHelp can connect you to a therapist who can support you, all from the comfort of your own home. Head over to betterhelp.com/AlAbdal or enter my name, Ali Abdal, during the sign-up process and enjoy a special discount on your first month. Anyway, thanks, BetterHelp, and let's get back to the video. All right, now we come to health habit number two, which is sun exposure. So we're going to talk about sun

exposure in general, and also sun exposure specifically in the morning. Okay, so let's start with sun exposure in general. Now, back in the day, having darker or tanned skin wasn't very desirable, and so they used lead in skin whitening makeup to try and make their skin a little bit more fair, fair, and beautiful as they say. The Greeks and Romans did this around 900 BC to 500 AD, and from the 1500s to the start of the 1900s, this was fashionable across Europe and America as well. But then everything changed in the 20th century where going to holiday to a hot sunny country and then getting more tanned suddenly became fashionable. But around the same time, scientists were discovering the links between UV radiation and skin cancer. So even though people still enjoyed spending time in the sun, we became more conscious of spending too long outside because we were worried about skin cancer. We're told by doctors and dermatologists and big Public Health bodies to always wear

Sun cream always put on your sunglasses, and always wear a big hat to avoid sun exposure. Apparently, this was actually a famous campaign in Australia in the 1980s: slip, slop, slap. Slip, slop, slap on a shirt, slop on sunscreen, and slap on a hat. This means slip on a t-shirt, slop on some sunscreen, and slap on a sun hat. Apparently, in some ways, sunlight has gotten a bad name for itself over the last 100 years because we've been really worried about skin cancer and aging of skin. But the truth is that sunlight can be both harmful and also beneficial for us, so we need to find some sort of balance. If you get too much exposure to the sun and UV light, that can cause skin damage, aging, and contribute to skin cancer. If you look at this picture, this is a truck driver where, because they've been driving on one side, like half of their face has been sun-exposed for a very long time, and the other half hasn't.

you can literally see the difference between like what sun does to skin, and what shade does to skin, and there's actually a really clear association between sun exposure and living longer. So this graph, for example, shows different age groups along the x-axis, and then they all-cause mortality per 1,000 person-years along the y-axis, i.e., how likely are they to die. This is what the line looks like for people who have been avoiding sun exposure. This is what the line looks like for moderate sun exposure, and this is what the line looks like for people who had the most sun exposure. Now, this doesn't seem like much, but if you zoom in on the graph, you can see that there's actually a pretty reasonable difference in all-cause mortality between these different groups. So essentially, the more sun exposure you get, the lower your chances are of dying in terms of all-cause mortality over time. And researchers in 2011 even came to this conclusion: the overall health benefit of an improved vitamin D status from sun exposure may be more important.

than the possibly increased CMM risk, which is a type of skin cancer resulting from carefully increasing UV exposure. And there are lots and lots of reasons for this. So you probably know that UV rays from sunlight help our skin make vitamin D, which means we absorb calcium and phosphorus to strengthen our bones. In theory, you could take a vitamin D supplement, but actually, even though lots of governments and public health bodies recommend vitamin D supplementation, the actual evidence for it is a little bit mixed. And what a lot of the studies around this show is that actual sun exposure is generally better for you than just taking a vitamin D supplement. In fact, this very recent study in 2024 concluded that multiple Trials of oral vitamin D supplementation show little benefit. So basically, the sun does things for our body that taking a vitamin D supplement doesn't really do. For example, you might not know that UV rays from sunlight actually cause our skin to release nitric oxide into our blood. And this makes our blood vessels relax and therefore reduces our blood pressure.

that's why, for example, you can see decreases in blood pressure in summer compared to in winter. So, sunlight helps protect against things like heart disease and strokes, and it also decreases our risk of things like obesity, autoimmune conditions like arthritis, and lots of different types of cancer as well, including apparently skin cancer. So, what I'm personally taking away from this is that I should probably spend more time in the sun. Yes, of course, I'm still going to use my sun cream, but like sun exposure is probably not as bad as we were led to believe. But the other thing around sun exposure is that if you are a fan of Andrew Hubman, which I am, like he talks a lot about getting sun exposure first thing in the morning. Now, because we are diurnal mammals, we want to be alert and active during the day, and then we want to be sleeping obviously at night, and we want all the cells and organs in our body to stay in sync with this day and night cycle, which is

called our circadian rhythm, or our internal clock. Now, there is a region in the brain called the suprachiasmatic nucleus in the hypothalamus, which is our Master Clock. This Master Clock sends signals to the rest of our body about whether to feel sleepy or awake. Now, the cool thing about the circadian rhythm is that it's actually slightly longer than 24 hours, and so we need cues from our environment to keep it in sync, and that is why light is so important. So, our circadian rhythm is most sensitive to sunlight first thing in the morning and also late at night, which enters through our eyes, hits the retina, and then sends signals to that Master Clock in our brain. So, first thing in the morning, firstly, sunlight increases our cortisol levels to make us feel alert and focused. Secondly, sunlight helps our bodies make serotonin, which boosts our mood and makes us feel happier. Thirdly, sunlight in the morning helps stop our body from making melatonin, which is the hormone that makes you feel sleepy. And fourthly

getting sunlight first thing in the morning tells our brain to set an internal timer, so that 12 to 14 hours later, you'll start to make melatonin again, and you'll therefore feel sleepier. In a nutshell, if you get sunlight fairly early in the morning, it basically sets your clock forward and makes it way easier to go to sleep and also wake up earlier. Actually getting light exposure in the evening, especially the blue light that mimics sunlight that comes from lots of devices and screens and phones, is generally not good because it reduces the release of melatonin, which makes us feel less sleepy. Blue light in the evening also delays our internal body clock, so you'll probably find it harder to go to bed early and you might wake up later as well. This is why people recommend that you set on the sort of Night Shift settings on your devices, so that it reduces blue light and makes the light more yellow. Or a lot of people wear blue light blocking glasses. Now I've

interviewed a couple of professors of sleep science and stuff on my podcast. They always say mixed things about blue light blocking glasses. Like are they useful, are they not? I don't know. I bought some like yesterday because I thought, you know what, let me take my sleep more seriously. And so I'm running a bit of an experiment on myself to see if blue light blocking glasses are actually useful. In fact, let me see if I can grab them. This is what they look like. They're super cool. Check this out. Boom. Yep, these are my blue light blocking glasses that I've started to wear for the last two nights in a row. And actually, on night one, my sleep score was 100%, and has never been that high. And yesterday was like 78%, and it's also not usually that high. It's usually in the '60s. I'm not sure if it's the blue light blocking glasses or just the that I've been taking my sleep a bit more seriously, so I'm sleeping a bit better.

but yeah, I mean, I thought I'd give it a go just to see what happens. Anyway, the important takeaways here are that sunlight is generally a good thing, and sunlight first thing in the morning is an even better thing. And so, as part of my thing that I'm doing to get the steps in first thing in the morning, I'm going for a walk around the local park for the first half an hour to an hour of the day. So hopefully, what that means is that I'll get my blue light in from the sunlight, and hopefully that also means I get my steps in completely for free. Now, if for whatever reason you cannot go outside first thing in the morning, then one thing you can do is you can open all of your windows and try and flood your room and your retinas with natural light. And by opening the windows, you won't filter out a lot of the sun's rays. And if you're in an environment where there's literally no sunlight, then what you can do is you can turn on lots of

your indoor lights so that you try and flood your retinas with some amount of light. Or you can get those fancy lamps and stuff that are supposed to mimic natural sunlight. Uh, I've never tried one personally, but I've heard from a few friends that they're quite good. And then finally, we come to hydration. So, you have probably heard the recommendation that you should drink at least 2 and 1/2 L of water every day. Now, this is a little bit baffling to me because I never drink 2 and 2 lers of water a day. And so, in this new health kick that I'm doing, I was kind of asking myself, should I actually be drinking 2 and 1/2 L of water? Cuz there's quite a lot of water to drink. Now, this recommendation to drink 2 and 1/2 L of water per day originally came from dietary guidelines that were published by the US Food and Nutrition Board of the National Academy of Sciences in 1945, which said 2500 Millers.

of fluid should be ingested on a daily basis, and even way before this in the 1800s, there was a thing called hydropathy, and hydropathists were people who thought that water could cure anything. And so, they told people to drink lots and lots of water. There was even this guy called Vincent Priet who said famously that water brings bad stuff out of the system. And to be honest, when it comes to hydration, you probably get a lot more water than you think from food. Like if you have any fruit, that's full of water. Even bread is like 40% water, which was kind of surprising. And so, I'm kind of skeptical about this. Like, do we actually need 2 and 2 L of water? I feel like I've never really drunk that much water, and I'm still alive. I know a lot of people who don't drink that much water, and they're still alive. What's like a good amount of water to drink on a daily basis? Now, what a lot of people don't is that this guideline from 1945.

was not actually supported by any proper scientific study. As this article says, this recommendation of 2 and half liters was repeated in the 1948 revision with no reference or authority cited in the calculation. Okay, so 2 and a half liters is probably not a scientifically validated recommendation, but we do know that staying hydrated is not actually a bad thing. Obviously, drinking too much water all at once can be bad for you, but we do have evidence for lots of positive effects of drinking water on our health. For example, if you are dehydrated, that can alter your mood, concentration, memory, and alertness. So, drinking water to the point that you are sufficiently hydrated is important for our mental performance. And obviously, if you're exercising as well, especially when you're doing endurance sports like running or cycling, we've got to stay hydrated so we can perform at our best, and so that we can regulate our body's temperature and so that we don't get as tired as quickly. Research also shows that our kidneys function better when

we're more hydrated, so it makes sense that low water intake is a risk factor for urinary and kidney diseases. Actually, we also apparently have strong evidence that mild to moderate hypohydration, i.e., underhydration, impairs several indices of cardiovascular function. Now, broadly from a of the research we've done on this, the conclusion seems to be that yes, you should drink water, but you shouldn't necessarily feel like you have to be hitting some arbitrary threshold of 2 and a half liters per day. Generally, if you follow your body's thirst cues, that will probably give you the water that you need, 'cause the body is quite good at regulating its own water levels and telling us to drink when we feel thirsty. One thing you can do that I do find quite helpful is this urine color chart. So basically, you can see how dark your wee is, and in theory, if your wee is in zones 1, 2, and 3, you're probably sufficiently hydrated. But if it is darker than Zone 4 of Zone 4 through to

8 you're probably a little insufficiently hydrated, and it's worth having a little bit more water, but broadly, there's not actually that much scientific evidence to support drinking loads of water or drinking water at specific times. Obviously, if it's a hot day and you're exercising and you feel thirsty, then yeah, you should drink water. One thing to keep in mind is that you probably don't want to drink a lot of water at night because you are likely to then wake up to go for a wee at nighttime, and it's probably better for you to get a full night's sleep without it being interrupted by having to urinate than it is for you to just drink loads of water at nighttime. But broadly, the advice here seems to be to just follow your own body's natural cues. Now, if you enjoyed this video, you're probably going to want to dive into a little bit more about sleep, and so you can check out this video over here, which is my evidence-based sleep routine that talks about all of the actionable

evidence-based recommendations for how you can get better sleep. Because sleep is the single best performance-enhancing drug, so check out that video over there. Thank you so much for watching, and I'll see you in the next video. Bye-bye.

3 Easy Habits to Improve Your Health (Evidence-Based)

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