Leah:
Hello and welcome to the Ideal Nutrition Podcast. I am Leah Heigl and I am here with my co-host Aidan Muir and today’s going to be a little bit of a short one and we’ll be answering the question, does coffee dehydrate you? The logic here is pretty simple in that we know caffeine is a diuretic. Diuretic is something that increases urination. So increases the amount of fluid output that we have in our system.
Therefore coffee could potentially be something that dehydrates you being that it contains caffeine. So there are a lot more layers to this than just that. Otherwise we could end the podcast here and be like, yes, it does dehydrate you. So obviously there’s a little bit more to it. So we’re gonna go through that now.
Aidan:
So stating the obvious, just because something is a diuretic like it increases your own production, doesn’t mean it necessarily needs to have a net negative in terms of you are now increasing urination by more than you were taking in. So the first place to obviously start there is by looking at research on this topic. So there was a meta-analysis that found 16 studies looking at this and they found obviously this very broad but consuming an average of 300 milligrams of caffeine in the form of 710 mL of coffee, keep in mind these are averages. So 710 mL of coffee increases urine production by 109 mL in comparison to drinking non-caffeinated beverages.
So, you can interpret that from a few angles. One is that the diuretic effect is real. We have a lot of areas of caffeine research. You can imagine that this may also scale a little bit based on tolerance. Like does it affect somebody who rarely has caffeine more than affects somebody who has caffeine? But let’s just take that out for a second and just be like, okay, it increases it a little bit. That’s a real thing, the diuretic effect.
The second is how practical or relevant is that? Does that really matter? Like if somebody’s like, having a cup of coffee is gonna dehydrate you. When we just looked at it being like having 710 mL of coffee, quote unquote dehydrated somebody by 109 mL, like that’s not crazy. Then the third is that when you look at it, 109 mL is not much in comparison to 710 mL. So clearly the coffee still had a net hydrating effect when you look at it from that.
Perspective, there’s where you can go into that. Keep in mind that these are just averages. I want to go really, really broad with this to give us a good foundation to start off with, the simple way of looking at it is there’s probably a net hydrating effect still in most cases.
Leah:
Yeah, I think also providing a little bit of context around the 300 milligrams of caffeine. If we’re talking like specifically coffee, that could be like three to five cups of coffee. Yeah. So that’s like talking a significant amount for an extra output of 100.
Aidan:
Yeah, I typically call like a shot of coffee about 80 milligrams is pretty variable. Some people just use 100 just like round up. It also it just depends on so many things.
Leah:
Yeah, it’s like on average, like three to five cups of coffee is probably about that amount of caffeine. Something else to consider is the habitual intake. A lot of caffeine research is skewed by habitual versus non-habitual intake. So people that drink coffee all the time and the impact on them versus people that are not habitual coffee drinkers and how it goes on to impact them.
Often participants will be withdrawn from caffeine for a period of time in studies like this, or they take on people who just do not consume caffeine. So typically there is this period of time where there’s no caffeine consumed and then they are testing some kind of effect of caffeine. The consensus is that the diuretic effect of caffeine coffee in general is significantly decreased if you drink coffee on a regular basis.
A study looking at this specifically got 50 habitual consumers of coffee to consume either 800 mL of water or 800 mL of coffee with about 4mg of caffeine per kilo body weight in addition to their habitual fluid intake, which was provided as water and had been measured in the lead up to this study. And there was no difference in urine production.
So perhaps if you’re someone who is habitually having three to five cups of coffee per day, this isn’t necessarily going to have a dehydrating or potentially even a diuretic effect at all.
Aidan:
Yeah. So like, while I say that the diuretic effect of caffeine is real, like when you look at it from the perspective of being like, well, what if you are a habitual consumer? Then maybe it’s not as real, just the same as blood pressure. Like if you do not habitually consume caffeine, and then you have a relatively high dosage and you measure your blood pressure, you will likely see an increase. That’s what the research has found, like it’s often an increase.
But if you habitually consumed caffeine at the same time every day in the same dosages every day, that increase if present at all will be much, much, much smaller. This is also another thing to think about when you are interpreting research on caffeine, because so many areas of caffeine research are a little bit skewed by this habitual versus non-habitual thing as well. But on this specific topic, we could go even deeper into the research if we wanted to, like really, no matter how you look at it, coffee, tea and other caffeine containing liquids still count towards hydration.
Maybe you need a tiny bit more liquid because of the small diuretic effect if you are somebody who that is going to be relevant for, but the effect is small and certainly doesn’t dehydrate you. If somebody is really going to nitpick about the exact words I’m using, they might be like, what if I had a like 30 or 50 mL shot of espresso that only has a tiny amount of liquid. And even then you’re like, this is probably still not like…
Leah:
And you’re not a habitual consumer, so it’s like a once off.
Aidan:
Yeah, so you’re gonna go real deep with this to maybe find a flaw in this. yeah, basically the short version is caffeine doesn’t dehydrate you.
Leah:
Yeah, I think that’s a good summary. And I think if you are concerned about dehydration, your first port of call is probably just drinking more fluids.
Aidan:
Shout out to our shortest podcast ever with an under seven minute time.
Leah:
That is definitely the shortest, but there is no like every way, every angle you look at this, you kind of came come to the same conclusion and it’s just super clear.
Aidan:
So as always, thank you so much for listening. If you have not already, please leave a rating and a review. We massively appreciate that.