Transcript
Avoid these three drinks because they can make your skin look older. 16 million views with the winning recipe of an appeal to fear and vanity coupled with an unqualified dietary rule. We can talk more about one and two in a different video, but let's skip to three. Number three was a real surprise to me because it is so healthy for you. Was a surprise? Oh, he must mean that he was surprised when he read the research study that his claim was based on. I'm excited to see it. It is coffee. damaging to the skin. Why is coffee aids the skin? Caffeine is what's called a diuretic. That means it dehydrates you. So caffeine can dehydrate the body and dehydrate the skin and make you look older. Now I'm not saying don't drink coffee ever again. If you do like coffee or drinks that contain caffeine and many of them are very healthy for the brain and for the body, make sure you drink plenty of water. That's it. No evidence. Just trust me because... You're new to my channel. Hi, my name's Robert Love. I'm a neuroscientist. Not that being a neuroscientist really has much to do with what he's talking about. Hi, Robert, I'm a visha. I'm a scientist who only makes recommendations based on cited evidence. But let's analyze his claim. Avoid coffee because it'll age your skin, because it's a diuretic, which dehydrates you, so actually just worry about drinking a ton more water. This gets a few things right, but relies on many assumptions, which is not how we do science. Let's break it down. First, yes, your overall body hydration level does impact your skin hydration parameters, not the same as aging your skin, because if you just drink more, then suddenly your skin bounces back and as good as new. No cause for fear. Next, yes, diuretics make you pee more, but when you lose fluids, your body does this weird thing where suddenly you want to drink more and replenish. It's, uh, what's that word again? Oh, thirst. Your body is pretty good at regulating your overall fluid balance, so a diuretic is unlikely to impact your skin, although there is some truth to this with elderly folks on diuretic medications. Anyway. relevant here because coffee does not cause dehydration and it's often not even a diuretic contrary to popular belief but that's why we rely on scientific evidence. As a great educator often says, time for school. See notes everyone! Coffee can be a short-term diuretic but mostly at high doses of caffeine. This study took coffee drinkers who typically consumed between one and three cups of coffee per day and based on their body weight gave them a cup of coffee with the equivalent of either six cups of coffee worth of caffeine, or water. They then took urine samples over the course of the next three hours. And only the four to six cup of coffee equivalent caffeine group, the high caffeine group, ended up peeing out any more than the group that just drank water. But that was still just three hours after drinking the coffee. And the body is really good at maintaining long-term balance. Another study used those same two doses of caffeine, this time in pill form, given over 11 days, while measuring 20 different biomarkers of full-body hydration status. neither dose of caffeine caused any amount of measurable dehydration. In fact, another study showed that caffeinated beverages work perfectly well for rehydration after exercise. So if you're a fellow coffee lover who's also a little bit vain, drink without fear for your skin. But yes, it does make you poop.
Additional notes
Does coffee age your skin? Make you pee? Does it even dehydrate you? There are lots of common misconceptions here. Some notes: 1. Few studies have measured the effect of more than ~6 cups / day (6mg/kg caffeine), so we know less about the effects in that range. 2. The study that showed 4-6 cups acting as a short-term diuretic showed it in folks where that was more than their habitual consumption. It could be that if that was their baseline, the diuretic effect would go away. Another study (PMID: 24416202) with a 4-6 cups / day cohort showed no diuretic effect at 4mg/kg. 3. As we get older, our bodies get a bit worse at maintaining hydration balance via thirst signals. As such, elderly folks taking diuretics do have to make more of a conscious effort to drink fluids (PMID: 34199738) 4. Exercise may reduce the diuretic effect of caffeine. 5. Women may experience a somewhat increased short-term diuretic effect as compared to men (PMID: 25154702) 📚 KEY STUDIES PMID: 28868290 PMID: 16131696 doi: 10.1046/j.1365-277X.2003.00477.x Here’s a systematic review from 2020 that I didn’t discuss explicitly but backs up all of the conclusions: doi: 10.1111/ijcp.13539 For a written versions of this video, with in-text citation, sign up for my newsletter! #science #coffee #edutok
References
- Original source notes.
- Hydration and skin physiology. PMID: 29392767.
- Caffeine, coffee, and fluid balance study.
- Caffeine ingestion and fluid balance. PMID: 16131696.
- Caffeinated beverages and rehydration after exercise. DOI: 10.3390/nu12051276.
- Additional caption references: PMID 24416202; PMID 34199738; PMID 25154702; PMID 28868290; DOI: 10.1046/j.1365-277X.2003.00477.x; DOI: 10.1111/ijcp.13539.