The Science of Hydration and Dehydration + 4 Simple Ways to Increase your Water Intake

By April Segal, PharmD, BCPS, APh

Remedy Pharmacist + Founder


The Science of Hydration

You may have heard the advice to drink 8 cups of water a day. That is definitely a good goal, but on average that isn’t even typically enough. The National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:

  • About 15.5 cups (3.7 liters) of fluids for men

  • About 11.5 cups (2.7 liters) of fluids a day for women

We also get water from foods, typically about 20% of our total water intake, so if you get 8 cups of fluids plus eat a pretty good variety of fruits and vegetables, you may be close to getting the recommended intake.

Other factors that increase your water intake needs:

  • Exercise- Any water lost through perspiration must be replaced. If you work out longer than 1 hour, you should consider electrolyte replacement too.

  • Environment- Heat, humidity or high altitude all increase fluid intakes

  • Health- Loose stools/diarrhea or vomiting cause major fluid losses. Intravenous fluids and electrolytes may be needed in these cases.

  • Pregnancy or breastfeeding - Women who are pregnant need 10 cups and those who are breastfeeding need 13 cups/day.

The best way to tell if you are getting enough? 

The color of your pee. It should be clear to pale yellow. Any darker than that and you need more water. Also you should be urinating about 3 times a day.

Health effects of being dehydrated

When we are dehydrated first we feel thirsty and fatigued, and may develop a mild headache. This eventually gives way to grumpiness, and mental and physical decline. By the time you feel thirsty your body is already dehydrated; our thirst mechanism lags behind our actual level of hydration. Research shows that as little as 1 percent dehydration negatively affects your mood, attention, memory and motor coordination. The underlying cause is less clear but it is thought to be that brain tissue fluid decreases with dehydration, thus reducing brain volume and temporarily affecting cell function.

As you 'lose' body water without replacing it, your blood becomes more concentrated and, at a point, this triggers your kidneys to retain water. The result: you urinate less.

The thicker and more concentrated your blood becomes, the harder it is for your cardiovascular system to compensate by increasing heart rate to maintain blood pressure. When your dehydrated body is 'pushed' – such as when exercising or faced with heat stress – the risk of exhaustion or collapse increases. This can cause you to be lethargic and light-headed. 

Eventually, as dehydration progresses, electrolyte imbalance occurs. The most common symptoms of electrolyte imbalance include headache and muscle aches. As imbalance progresses, in the case of severe dehydration, this can also lead to life-threatening heart rhythm abnormalities.

Other benefits of remaining hydrated:

  • Weight loss: Drinking more water delays hunger pangs and random cravings. It also increases the body’s metabolism. Some studies have shown that people who increased their water intake while dieting lost more weight than people that kept water consumption to minimal levels. As a plus, if you’re thirsty while on the go, you’ll have something on-hand right away, so you won’t be tempted to indulge in a soda from the nearest convenience store. Craving sugar? Add fruit to your water for a healthy beverage that quenches your thirst.

  • Plump skin: Skin is the largest organ of the body. Regular water consumption improves the texture and elasticity of the skin, as the cells are allowed to function properly. Staying hydrated also helps the skin regulate body temperature through sweating.

  • Joint Health: Water helps keep the cartilage around joints hydrated and soft. And when that cartilage is hydrated, your joints can move with ease. Think of water as the oil that lubricates your joints.

Simple ways to increase your water intake:

  • Carry around a fun water bottle that you love. Keeping this around is basically a constant reminder to drink.

  • Change up the temperature of your water. From popsicles to teas, you can increase your intake by simply changing the temperature of your water. 

  • Sparkling water- there are plenty of great options out there from La Cruix to Spindrift, or make your own. And yes, sparkling water has shown to hydrate you just as well as regular water.

  • Use a reusable straw- drinking out of a straw helps you consume more water with each “water break” sneaking in extra ounces.