Your Biggest Hydration Questions—Answered!

By Cassandra Forsythe, PhD, RD

You know water’s good for you and that dehydration is bad. Beyond that, however, the topic of hydration leaves many people with more questions than answers. Luckily, we’re ready to quench your thirst for the truth about water and hydration, and some of our answers may surprise you!

“Do I have to drink eight 8-ounce glasses of water each day to stay hydrated?”

The “eight 8-ounce glasses” recommendation gets thrown around all of the time, but how accurate is it, really? And why has this become the standard recommendation?

Every day your body loses some water through urine, sweat, respiration (breathing), and other necessary metabolic processes. So if you don't consume enough water, you can become dehydrated, and experience symptoms such as headaches, tiredness, and difficulty concentrating. Chronic dehydration can also disrupt normal, healthy bodily functions and contribute to a number of issues such as constipation and kidney stones—and who has time for that?


Water makes up about two thirds of your body, with high concentrations in our muscles (about 70 percent of our muscles’ weight comes from water) and in our blood. In women, water makes up about 50 percent of our total body weight. However, since fat cells are devoid of water, in both lean women and men (who typically carry less body fat than women) water will make up an even greater percentage of total body weight.

hydration-woman-outdoors-sunset-450x338What’s more, water is important for the regulation of body temperature (thermoregulation) and ideal exercise performance. When you experience exercise-induced dehydration (that is, you lose two percent or more of your body weight from sweating and inadequate water intake during exercise), it will very negatively affect your ability to exercise to your full potential, and can have serious health consequences1. Therefore, drink plenty of water before, during and after exercise to make sure you can put forth your best effort at each exercise session.

“So, how much do I need to drink, exactly?”

The oft-repeated recommendation for eight, 8-ounce glasses of water each day equates to 64 ounces, or about two liters, daily. However, more specific recommendations from the Institute of Medicine (IOM) and the U.S. National Academy of Sciences, suggest you should be drinking even more. These experts state that healthy adults, between the age of 31 and 70, living in temperate climates, should consume the following amounts each day:

  • Men: 125 ounces (3.7 liters) of water per day from all dietary sources,which include drinking water, tea, coffee, flavored waters, and food. (More on how food can hydrate you later!)
  • Women: 91 ounces (2.7 liters) of water per day from all dietary sources.

Just like most nutrition recommendations, however, these recommendations are made for the average population, and they’re not individualized for you, or me.

Every body is different, so of course, our specific needs will usually vary.

This is where individualization comes in. Recently, a very well-controlled study conducted at the University of Connecticut, by one of the foremost experts on hydration, looked at normal fluid intake and hydration in healthy women3,4. The study found that the average 24-hour fluid intake volumes was quite large, spanning 0.89 to 4.40 liters per day. Low fluid intake did not always mean that a woman was dehydrated. Some women simply have a lower water requirement.

One big correlation is urine output. It’s no surprise that the more fluids you drink, the more you’ll pee. You may not require a lot of water compared to your training partner, but how do you know if you’re properly hydrated or not? The best things you can do are:

  • Monitor your mood. If you notice more tension, depression, or confusion, drink up! (With water that is.)
  • ggs-urine-color-table-350x231Use this urine color table as a guide. Understand that from the recent research collected above2,3, that urine color numbers less than or equal to 4 are still healthy and hydrated. It is actually uncommon/rare for women to achieve a urine color of 1 or 2.

Also keep in mind that if you have recently take a multivitamin, the B-vitamin content may turn your urine bright yellow. There’s nothing to be alarmed about, and it’s not related to dehydration, in that case.

What’s more, these recommendations are for people living in temperate climates. So when temperatures soar, you will need more water than this. On hot days, aim to consume at least eight extra ounces, and make sure to drink a fluid that contains electrolytes (sodium, potassium, chloride)—though not necessarily one that contains added sugar—to aid in nutrient absorption. Including electrolytes can help you avoid hyponatremia. Hyponatremia can happen when you drink too much water and throw off your electrolyte balance, which lowers your blood sodium levels. In serious cases this can lead to death.

If you tend to sweat excessively during exercise, you might want to measure your body weight before and after your workout. Rehydrate properly by drinking 16 ounces of water for every pound of weight you lost during your training session (or one liter of water for every kilogram).

“Can hydration really impact my mood?”

It’s possible that your water intake is greatly related to your mood state. Don’t believe it? There’s science to support this.

In a 2015 study conducted at the University of Connecticut, it was shown that adequate fluid intake led to improved mood2. The researchers recorded total dietary water intake and mood states in 120 healthy young women over a five-day period. All the women in the study were on oral contraceptives to ensure hormonal homogeneity among participants. The researchers accounted for known mood influencers such as macronutrients, exercise, and caffeine. They also accounted for other mood variables such as illness, use of prescription drugs, alcohol intake, and family medical history.

Overall, they found that water intake predicted total mood disturbance more than any of the other known mood influencers. Women who habitually drank more water had more favorable mood states. Specifically, total water intake related to lower or higher levels of tension, depression, and confusion (i.e., the better the water intake, the less tension, depression, and confusion experienced).

As stated by the researchers, “These findings, however, are not able to distinguish improved mood state as a function of (1) upbeat/positive women tending to consume more water, or (2) if drinking water enhanced mood state in these women.” So, although the results are highly statistically significant, it’s possible that they may not be clinically significant, even though previous research does support that reductions in body water and dehydration are associated with more pronounced fatigue, tension, and confusion.

Overall, it can’t hurt to drink more water and consume more water-rich foods/beverages (more on that below), and it might even improve your mood!

“What if I just don’t like drinking water?”

It’s not uncommon for some women to feel sick to their stomach just thinking about drinking the recommended amount of water. If you’re one of these women, consider that your total water intake comes from all of the following sources:

  • Drinks, either plain water or other beverages and fluids. This includes tea, coffee (yes!), juice, and soups.
  • Solid foods, especially fruit and vegetables, as well as foods that absorb water, like oatmeal and lentils.

So, if you don’t like drinking tons of water straight up, you can still meet some of your water needs through other beverages like coffee, and high water-containing foods like fruits and vegetables. Food provides about 20 percent of your total water requirement each day (and more if you eat a lot of vegetables and fruits).

That means that you’ll need to drink at least two to three liters (about 64 ounces) each day of some type of water-containing beverage. Thus, the general recommendation of eight 8-ounce glasses of fluid is pretty close to being correct. Keep in mind, too, that some women naturally drink more water than others, especially active women.

“Wait a hot minute. Does coffee really count toward my total daily water intake?”

Yes! In fact, coffee is a reasonable way to get in your fluids. Think about it: What is coffee made up of? You guessed it: Water!

And no, though the myth persists, coffee is not a diuretic (meaning it does not cause you to become dehydrated). In fact, Dr. Lawrence Armstrong from the University of Connecticut was the first researcher to disprove this dehydrating myth in a research setting5. In this controlled, 11-day study, he showed:

  • When you consume caffeine or a caffeinated beverage, your body retains some of the fluid.
  • Caffeine consumption causes a mild diuresis very similar to that of water (water, when consumed in large volume, increases urine output).
  • There is no evidence that consumption of caffeinated beverages causes a fluid-electrolyte imbalance that is detrimental to health or exercise performance.
  • A person who regularly consumes caffeine has a higher tolerance to the mild diuretic effect.

If water isn’t your thing, coffee can help you meet much of your water needs.  (Just go easy on the sugar and sweetened flavor add-ins!)

“What are the best beverages to drink to boost hydration?”

hydration-flavored-waters-450x275To meet your daily hydration needs, these are the beverages I highly recommend, with amount listed beside each one. First and foremost, water is at the top of the list. If you don’t like the taste of your normal plain water, try filtered water or add a touch of lemon to make it a little more palatable.

Level 1 — MOST Important

  • Plain water – drink a minimum of 20 ounces (0.5 liters) each day if you will be getting fluids from other sources, or aim for at least 64 ounces, if water is your beverage of choice.

Level 2 — Contain No Calories, Artificial Sweeteners, Caffeine, and Chlorine

These beverages can replace an equivalent amount of water. Consume up to 40 ounces per day.

  • Sparkling mineral water, unsweetened
  • Naturally decaffeinated tea – white, green, oolong, black, rooibos, tulsi, herbal (If naturally decaffeinated is not possible, go with the decaf option you have available to you.)
  • Naturally decaffeinated coffee

Level 3 — Contain No calories and Artificial Sweeteners

These beverages also can replace an equivalent amount of water, but try to limit your intake of caffeine to no more than 250 mg per day (one eight-ounce cup of coffee contains about 80 to 140 mg of caffeine). To see a caffeine chart of beverages, click here.

  • Caffeinated tea – white, green, oolong, black, yerba mate
  • Caffeinated coffee, espresso

Level 4 — Contain Some Protein, Carbohydrates, and Fat

These contain about 80 percent water content. Consume 0 to 16 ounces per day.

  • Dairy Beverages – goat’s milk, cow’s milk, organic grass-fed if possible
  • Non-Dairy beverages – almond milk, hemp milk, rice milk, all unsweetened

Level 5 — Contain Mostly Carbohydrates

Consume up to eight ounces of these types of beverages per day if desired. Ideally, limit these types of beverages due to their high simple carbohydrate (sugar) content, which can lead to excess energy intake and blood sugar fluctuations.

  • 100% fruit juice – no added sugar or artificial sweeteners
  • Coconut water
  • Soy beverages

I hope this article has cleared up some of the most common misconceptions about water and hydration that you might hear and read everywhere. If you know someone thirsting for this information, pass them the link and share the knowledge!

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About the author:  Cassandra Forsythe, PhD, RD

Cassandra Forsythe, PhD, RD, CSCS, CISSN is an Assistant Professor at Central Connecticut State University (CCSU). She is a mother, entrepreneur, health and fitness enthusiast, and the author of The Modern Woman’s Guide To Good Nutrition. Cass is also on the advisory boards for Women’s Health magazine, and You can learn more about Cass on her website.


  1. Effects of hydration state and resistance exercise on markers of muscle damage. Yamamoto LM, Judelson DA, Farrell MJ, Lee EC, Armstrong LE, Casa DJ, Kraemer WJ, Volek JS, Maresh CM. J Strength Cond Res. 2008 Sep;22(5):1387-93
  2. Habitual total water intake and dimensions of mood in healthy young women. Muñoz CX, Johnson EC, McKenzie AL, Guelinckx I, Graverholt G, Casa DJ, Maresh CM, Armstrong LE. Appetite. 2015 Sep;92:81-6. doi: 10.1016/j.appet.2015.05.002. Epub 2015 May 8.
  3. Hydration biomarkers and dietary fluid consumption of women. Armstrong LE, Johnson EC, Munoz CX, Swokla B, Le Bellego L, Jimenez L, Casa DJ, Maresh CM. J Acad Nutr Diet. 2012 Jul;112(7):1056-61. doi: 10.1016/j.jand.2012.03.036
  4. Markers of the hydration process during fluid volume modification in women with habitual high or low daily fluid intakes. Johnson EC, Muñoz CX, Le Bellego L, Klein A, Casa DJ, Maresh CM, Armstrong LE. Eur J Appl Physiol. 2015 May;115(5):1067-74. doi: 10.1007/s00421-014-3088-2. Epub 2015 Jan 7.
  5. Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption. Armstrong LE, Pumerantz AC, Roti MW, Judelson DA, Watson G, Dias JC, Sokmen B, Casa DJ, Maresh CM, Lieberman H, Kellogg M. Int J Sport Nutr Exerc Metab. 2005 Jun;15(3):252-65.

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