Emily Wade (Host): At MIT, it seems like everyone has an emotional support water bottle. Campuses full of people toting Nalgenes and Stanleys and Owalas and Yetis, and tracking their ounces on apps and stressing about peak hydration. Today, we're settling a debate between two friends. Do those eight glasses a day count if your water is fizzy like this? If your water is plain and flat and boring, is that the only way it'll be actually hydrating you?

On this episode of Office Hours, I'm talking to n Nurse Practitioner Ally Sherwood from MIT Health's Primary Care Service, and she's going to help us separate the science from the seltzer. Welcome, Ally.

Allison Sherwood, MSN: Thanks, Emily. I'm excited to be here to help to settle the debate.

Host: Yeah. As you can see, I'm really, really invested in this debate. So, I'm going to just get right to the question. Dear Office Hours, I love seltzer. If water isn't fizzy, I don't want it. But a friend just told me that sparkling water doesn't count toward those eight glasses of water we're supposed to drink every day. They can't be right, right? It seems to me that water is water. Who is right? This is like Judge Judy or something. What's the verdict? Is bubbly water, does that count as water, or do you have to just have flat water?

Allison Sherwood, MSN: know, I think our listener is right. Water is water, whether it's bubbles or not. And when it comes to saying adequately hydrated, sparkling water is actually just as good as plain water.

Host: Oh. Well then I guess we're done here. I guess that is a pretty short podcast. You know, we can make this like a reel or something. Well, I guess we should probably say a little more, because I'm always a person who cannot be on a Zoom without having, like, multiple beverages. I was looking here at my coffee. What about coffee and tea? Because they're diuretics. So, do they count as a hydration tool?

Allison Sherwood, MSN: There's a greater truth there that coffee is a mild diuretic. And caffeine increases blood flow to the kidneys, and it does inhibit the reabsorption of sodium and water, which of course is going to promote increase urine production. So, in other words, you're going to pee more when you drink coffee. But there's still a lot of liquid in that coffee cup. So, it doesn't all count, but studies show that the average person retains between one-half and two-thirds of the fluids consumed when we have the caffeinated beverages.

Host: So, still it's kind of a net gain. So, I'm getting like some partial credit here with my cup of morning Joe.

Allison Sherwood, MSN: Yeah. I like that. So, you know, if you're someone that drinks coffee and tea regularly, National Academies of Sciences, which is kind of a big deal, actually lists coffee, tea, juices, and even soda as sources that can contribute to our total hydration.

Host: This is great. So, my seltzer counts, my coffee counts. And obviously, I'm not consuming this right now, but this occurs to me, what about alcohol? That's a liquid. Does that count on this hydration chart?

Allison Sherwood, MSN: Excellent question. And that's where I think we need to, you know, kind of dive into this deeper, because alcohol is a big exception to the liquid is the liquid rule. A pint of beer or a glass of wine, even alcohol seltzer is technically a liquid, but alcohol is a much stronger diuretic than caffeine, which is why you might make more trips to the bathroom when you're out of the bar at a restaurant when you're drinking. But alcohol works differently in the body than caffeine does.

Host: How so?

Allison Sherwood, MSN: Well, caffeine mildly suppresses the reabsorption of sodium and water. Alcohol, on the other hand, inhibits the production of vasopressin, which is a hormone that tells your kidneys to reabsorb the water when it's needed in your body. Alcohol switches the signal off, so instead of liquid being reabsorbed by your kidneys, your bladder fills up with urine and the end result is you have to pee more often.

Host: So unlike coffee where you're maybe keeping about like half or two-thirds of the water, with alcohol, you might be losing more liquid than you're consuming.

Allison Sherwood, MSN: Exactly. It's often a net loss. And well, you know, you should feel free to enjoy your coffee and seltzer if hydration is the goal. Please don't swap out your water bottle for that pint glass.

Host: Darn, darn Just kidding. Let's go back to the numbers a second. We always hear eight glasses a day, And that measurement always stresses me out because a glass is not a unit of measure. So I'm always like, I don't even know what that means. But even so, if I'm counting water and seltzer as full credit and I am giving partial credit to coffee and tea, how am I making sure that I am sufficiently hydrated during the day?

Allison Sherwood, MSN: It's a good question. And actually that drink eight classes of water a day rule isn't actually as scientific as we might like to think. For different patients and different folks, it might be a different quantity recommended.

Host: But it's eight classes a day. I feel like it's like everybody—that's what they say. Like, it's the instructions. What do you mean?.

Allison Sherwood, MSN: I hear you. And I know we all love to play by the rules. I love it. And I appreciate the sentiment for sure. One thing most people often don't consider is that hydration's not just about drinking, it's also about eating. So, moisture in the foods can account for about 20% of our total water intake. When you eat a piece of fruit, a serving of veggies, or some soup, you are actually eating your water.

Host: All right. So, we're getting hydration from our water bottles, our coffee break, our meals. So like, you can actually maybe have some emotional support soup, and that's still going to be hydrating. is there any harm though? I mean, you know, I go to the gym sometimes and you'll see somebody with like a giant bottle that's like a gallon jug or something. is there anything wrong with actually, you know. super hydrating, hydrate maxing, if we're using like the terms of today?

Allison Sherwood, MSN: Yeah. Yeah. It's an excellent question. For healthy individuals, drinking when you're thirsty and consuming beverages with meals is usually enough, to be totally adequate to maintain our hydration. Now, I think you bring in the gym question, which is an interesting one, which is when we're exercising and we're losing salt and fluids, we do need to be accounting for that. But that might be a different podcast.

Host: So if you're not breaking a sweat, you don't necessarily need to be toting around like that comically large jug of liquid with you at all times.

Allison Sherwood, MSN: You got it. And they're pretty cumbersome for any of us who've tried it.

Host: I mean, it's like maybe it's more of a bicep workout, but otherwise...

Allison Sherwood, MSN: Again, we'll get into a strength training podcast on another day.

Host: Yeah. We'll do that with Get Fit or something.

Allison Sherwood, MSN: I like that.

Host: So if we need something to kind of replace that eight glasses goal, is there a golden rule? Do we need a rule at all? Or is it, "It's MIT. We need to follow rules"? Like, what should we do?

Allison Sherwood, MSN: Yeah, it's a good question. And I think that we want to make sure, that we're not forcing it. So aside from feeling bloated, excessive liquid intake can wreak havoc on our daily schedule and make us a whole lot less efficient and productive. I see patients who feel guilty that they don't drink the eight glasses a day. But the ones who do meet eight glasses a day, often complain of things like peeing too much, getting distracted at meetings, or even peeing in the middle of the night, which is going to disrupt the really important piece of sleep hygiene.

Host: And sometimes when that happens, like your cat wakes up too, and then they want you to feed them, And then, you know, like a chain of crises right there. So, I can definitely try to adhere to that too, to not overhydrating for those reasons. So to recap, our listener is right, which is great news for me as a person who hates just flat water, so I'm thrilled to hear this. Sparkling water does count, and your coffee counts too, but maybe don't reach for that White Claw that's not going to hydrate you. Even if it looks like it maybe has a health halo, it really doesn't.

Well, this is great. Ally, I feel like you've cleared up some confusion for us and definitely saved us from some unnecessary trips to the bathroom and saved me from having midnight cat attacks. So, that's really great.

Allison Sherwood, MSN: I'm happy to be here. It's been my pleasure. And I think the theme continues to be consistent about listening to our body and its needs.

Host: Well, that's great. And if you need a clinician who listens to you like Ally, who is really good at that, our primary care team is always accepting new patients, and we're ready to help you thrive. You can make appointments online. If you have a question for Office Hours, a big one, a little one, a quirky one, a weird one, visit health.mit.edu/thrive and submit your question today. And thanks so much for being on this episode of Office Hours.