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What You Need to Know About Hydration

by Stephanie Margolis, R.D.

Water is vital for our health, making up 70–75 percent of our body mass. Water also works to transport nutrients, maintain a normal body temperature, lubricate and cushion joints, protect your spinal cord, and help get rid of waste through urine, sweat, and bowel movements (because if I say “poop” my kids will lose it in laughter).

We must be constantly hydrating our body throughout the day because we are constantly losing water—when we breathe, urinate, sweat, and even lay still, because our metabolism needs water. If it is hot outside or you’re exercising (especially outside), these losses happen even faster. Here we are going to talk about how much water we need, and how to get more of it each day.

Why So Much Pressure on Hydration?

You hear a lot about hydration because of all reasons mentioned above but also because with just a 2 percent loss of body water you can start to see symptoms of dehydration. These include:

  • Feeling thirsty
  • Dry mouth
  • Dry skin
  • Tiredness or fatigue
  • Headache
  • Decreased cognitive function
  • Reduced exercise capacity
  • Attention deficits
  • One study even showed adults’ arithmetic efficiency decreased with a 2 percent water loss (if you’re helping a kiddo with math, drink up!)

Avoiding dehydration helps to prevent constipation, UTIs, and kidney stones. Our body is constantly trying to achieve homeostasis—a state of balance—and having enough water is key in this process.

How Much Water Do I Need?

The amount of water you need varies based on your body weight, activity level, environment, medical conditions, and if you are pregnant or breastfeeding. While the 8×8 rule is widely known (drinking 8, 8-ounce glasses daily) it is not evidence based, and truly the upper and lower limits of water intake are yet to be established.

Through several studies, science has found that the median (middle of the range) amount of water women over the age of 19 need about 11 cups per day, or about 91 ounces. If you are pregnant you need 2–4 cups more (17–34 ounces), and breastfeeding requires 3–5 cups more daily (23–37 ounces).

I often get the question: “Can I drink too much?” The answer is yes, but it’s rare. When you drink large amounts of water too fast your kidneys cannot get rid of it. When this happens you start to dilute the level of sodium in your blood. This is called hyponatremia and can lead to nausea, vomiting, cramping, weakness, headache, or confusion. If you are a healthy individual drinking moderate amounts of water you should be absolutely fine.

Water and Exercise

We’ve talked about how to eat pre- and post-workout, you have access to amazing fitness programs with Lindsay, and now hydration is a third pillar to include in your health. If you begin a run or workout dehydrated, you will not be able to make up for that during your workout which can impact how hard you can push or the mileage you can cover. How much to drink? Here come the numbers:

  • Aim to drink 1 cup per 50 pounds of body weight of water over a two to four hour period before a workout. If you workout first thing in the morning this can be a challenge but enjoying a cup of water 10–20 minutes before your workout should be adequate.
  • If your workout is 60 minutes or more, or you work up a big sweat, you will need to hydrate during your workout.
  • If you are a salty sweater (blame those genetics), you will need to hydrate and rehydrate with water and some type of electrolyte drink. Not sure if you’re a salty sweater? If you have white marks on your hat or clothing after a sweaty workout, get muscle cramps often, or have sweat that stings your eyes, it is likely you are losing more sodium than average when you sweat.
  • After a workout, the most accurate way to figure out how much you need to rehydrate is body weight measurements. You want to drink 15 ounces for every 1 pound lost.
  • Fun fact: you often hear that milk is a great post-workout drink but do you know why? Milk has carbs, protein, and electrolytes, so it helps your muscles recover, replenishes your carbohydrate stores, and helps rebalance your electrolytes after a sweaty run.

If you’re not into the numbers, just paying attention to the color of your urine will let you know if you need to drink more. Light yellow indicates you are adequately hydrated. The darker the urine, the more hydration you need to do. (1)

Water is Booooring Though…

I get it. It can feel like more of a task than something you enjoy. But hopefully after reading the “why” behind water, you are feeling motivated to drink up! Here are a few tips to increase your water intake:

  • Carry a water bottle with you
  • Set a reminder on your phone every few hours cueing you to drink
  • Make a rule: water with every meal
  • Add flavor (try these immune and flavor boosting ideas)

Remember you don’t have to just get your hydration from water. Any non-caffeinated*, non-sugary beverage counts, and some foods too! Fruits and vegetables are 80–99 percent water with berries, melons, oranges, grapes, and lettuce leading the pack. There is an (*) behind caffeine because drinking coffee and tea can count towards your water needs for the day but once you hit over 250mg of caffeine (the amount in about 2 cups of coffee and 7 cups of tea) it starts to have a diuretic effect and can actually begin to dehydrate you.