How Much Water Should You Drink in a Day? A Doctor + Nutritionist Settle the Debate

Hydration's a hot topic these days. Refillable water bottles (decked out with some cute stickers, please!) are practically a fashion accessory in their own right. And there's no shortage of celebs and influencers preaching the perks of plain water as one of their favorite stay-healthy tips. So how much water should you drink in a day, really?

The answer might surprise you. While you're probably familiar with the recommendation to drink eight glasses of water per day, many experts say that probably isn't enough. Here, we settle the debate once and for all, plus talk about which drinks (and foods) count towards your daily hydration goal.

Hydration matters year-round

Our bodies consist of around two-thirds water, which forms the basis for saliva, blood and joint fluid. And it's a must for proper cell functioning. Since we're losing it 'round the clock — from sweating, urinating and even just exhaling — it needs to be replaced just as often, regardless of the season. "Even on a cold winter's day, our bodies continuously lose fluid through various processes," says Elizabeth Sharp, MD, founder and medical director at Health Meets Wellness.

And while anyone can become dehydrated, women over 50 may be particularly prone to the condition. Why? Menopause symptoms like night sweats and hot flashes may cause you to lose more fluids. Believe it or not, "it's the same potential for dehydration as someone who's sweating from exercise," Dr. Sharp says.

Age-related muscle loss factors in, too. "Muscle tissue holds water, and without enough muscle, your body will hold less water and have a higher likelihood of dehydration," explains Rachel Macpherson, CSCS, exercise nutritionist, certified personal trainer and CURE fitness advisor. In other words, there are more reasons than ever to sip, sip, sip.

The benefits of staying hydrated

Here's a look at keeping your fluid intake up can do.

1. It boosts energy and focus

Your brain is a whopping 75% water, and even a slight decrease in fluids has been shown to zap energy, short-term memory and ability to concentrate, reveals a study in the International Journal of Environmental Research and Public Health. "I've found in my practice that something as simple as drinking more water can actually improve mental clarity and energy levels, and keep energy levels more consistent throughout the day," Dr. Sharp says.

2. It supports weight loss goals

More than a third of people mistake thirst for hunger. If you're among them, simply reaching for a glass of water might satisfy your appetite just as much as a snack, notes Dr. Sharp, warding off accidental overindulging. (Interested in another easy way to shed unwanted pounds? Learn how fathead pizza dough speeds slimming.)

3. It protects your joints

Getting enough to drink might help smooth out some of those age-related aches and creaks. "You need proper hydration for optimal joint functioning, since your joints are surrounded by fluid that eases movement," Macpherson explains. "Without enough hydration, you can start to feel tight and sore from reduced lubrication."

4. It wards off headaches

Sometimes, drinking more water can stop head pain from starting in the first place. that's because dehydration is a known migraine trigger. In fact, frequent headache sufferers who increased their water intake by 1 liter (a little over 4 cups) per day decreased their total headache time by 21 hours over the course of two weeks, found a study in the European Journal of Neurology.

5. It curbs UTI risk

Move over, cranberry juice. Older adults prone to urinary tract infections who drank seven glasses of water a day experienced 58% fewer UTIs and compared to those who drank less, found a BMJ Open Quality study. Experts suspect that more fluids could help flush lingering bacteria out of the bladder before it's able to cause an infection.

See also: Dehydration Can Be a Sneaky Cause of High Blood Pressure — Here’s How To Replenish Fluids Fast

How much water should you drink in a day?

Now that you know what downing more H2O can do for you, one question remains: How much water should you really drink in a day?

Dr. Sharp recommends sticking with the guidelines from the U.S. National Academies of Sciences, Engineering and Medicine. "They state that women need roughly 2.7 liters of fluids a day," she says. That's around 91 ounces, or 11.5 cups. You'll get about 20% of that fluid from water-rich foods like fruits and veggies. "You don't need to get all of your water from drinking glasses of water," Dr. Sharp adds.

And you might need even more water if you're exercising or doing another activity that makes you sweat heavily (like gardening in hot, humid weather). In that case, offset the extra fluid loss by drinking 16 to 20 ounces of liquids two to three hours before you plan to be active. And take a couple sips every 15 to 20 minutes while you're exercising, Macpherson says. "When you're physically active, you lose almost twice as much water as when you're at rest," she adds.

The best drinks for hydration

Plain, simple water really is the best choice for staying hydrated. That's because it's naturally free of calories or added sugar. "I'd recommend flavoring it with a squeeze of lemon, a slice of orange, or mint," Dr. Sharp says, to punch up the flavor in a healthy way.

That said, when you need to switch it up, these options are also good choices:

1. Sparkling water

Bubbly water is still just water, albeit with some extra carbon dioxide for tongue-tingling bubbles. Since it's free of calories and sugar, it's just as good as the gold standard H2O. (Learn how an emotional support water bottle can help you reach your hydration goal.)

2. Herbal tea

Caffeine-free teas like chamomile or rooibos count towards your fluid intake for the day, Dr. Sharp says. The fact that they're calorie- and sugar-free also makes them a good choice, so be mindful about adding extras like milk or sugar. If you want a bit of sweetness, try a calorie-free sweetener like stevia or monkfruit instead, she recommends. (Consider sipping oregano tea, which has a slew of health benefits.)

As for caffeinated teas and coffee? While it's fine to enjoy both in moderation, you shouldn't count either drink toward your daily fluid quota, say Dr. Sharp and Macpherson. (The same goes for alcohol, too.) All are diuretics, which cause your body to expel out more fluids than you take in from drinking.

3. Raw fruits and vegetables

Fresh produce like cucumbers, celery, radishes, lettuce, grapefruit, strawberries and melon all contain at least 90% water (along with fiber, vitamins and minerals), so help yourself to a side salad or fruit salad. "One of my favorite hacks is to switch orange juice for an orange. That way, you hydrate and get fiber and prebiotics from the pulp of the fruit," Dr. Sharp says.

4. Coconut water

It's a favorite of Dr. Sharp's for rehydrating after a workout. "It's a natural source of electrolytes and has some calories for athletes who are exercising, so it's a great option," she says. Look for 100% coconut water that's free of added sugar, like Zico 100% Coconut Water or Harmless Harvest Organic Coconut Water.

5. Electrolyte drinks

These contain calories and minerals like sodium and potassium aimed at offsetting the loss of electrolytes from heavy fluid loss or sweating. "I usually only recommend them for people with a gastrointestinal illness [who are losing fluids from diarrhea or vomiting] or people who are engaging in a lot of strenuous exercise," Dr. Sharp says.

The best electrolyte powder is one free of artificial flavors and sweeteners, Macpherson points out. Some options to try: LMNT Electrolyte Drink Mix, Promix Electrolyte Drink and Cure Hydrating Electrolyte Mix.

For more ways to stay hydrated and healthy:

Dehydration Can Be a Sneaky Cause of High Blood Pressure — Here’s How To Replenish Fluids Fast

Do ‘Hydration Multipliers’ Actually Work? It Depends, Say Experts

Need to Drink More Water? The Trick May Be Using an Emotional Support Water Bottle

This content is not a substitute for professional medical advice or diagnosis. Always consult your physician before pursuing any treatment plan.