Who needs to drink more water? 8 groups for whom it matters most

Who needs to drink water? Everyone. But for some people, getting enough takes more deliberate effort: they lose more water through exercise, heat or illness; they need extra during pregnancy and breastfeeding; or they can’t rely on thirst, like young children and older adults. Some everyday habits crowd water out, too. And a few people need to be careful about drinking more, not less.

This is the second article in our series “Five rules of drinking water,” based on the book 5 Fundamental Postulations of Drinking Water by Prof. Oleh Pokotylo — Professor, Academician, Doctor of Biological Sciences (Ternopil, 2021). Below: eight groups, what US health authorities recommend for each, and how to make it easy.

When you lose more water: exercise, heat and sick days

The CDC names four times your body needs more water: in hot climates, when you’re more physically active, when you have a fever and when you have diarrhea or vomiting.

1. Active people and athletes

Muscle is about 80% water, Prof. Pokotylo notes, and a hard training session can cost anywhere from 34 to 135 fl oz (1–⁠4 L) of sweat. The American College of Sports Medicine suggests keeping losses under 2% of body weight and weighing yourself before and after a workout to learn your sweat rate. Prof. Pokotylo’s routine: drink well, but no later than 30 minutes before you start; take a few sips about every 15 minutes during the session; and replace the rest afterward. On hot days, the CDC adds, drink more than usual and don’t wait until you’re thirsty.

Athletes are also among the most studied groups in hydrogen water research: in a small pilot study of 10 male soccer players, blood lactate rose during heavy exercise after placebo water but not after hydrogen-rich water (Aoki et al., 2012). The research is still early; more in Hydrogen water and sports.

2. Anyone in the heat, doing hard physical work or at high altitude

On a hot day you can sweat a lot without noticing. NIOSH calls drinking enough fluids one of the most important things you can do when working in the heat. Its advice: about 1 cup (8 fl oz) every 15–⁠20 minutes, because small, frequent drinks work better than a lot at once — but no more than 48 fl oz (1.5 quarts) an hour. Very active people who spend their days in hot weather often need 200 fl oz (6 L) or more of total water a day, the National Academies note. High altitude can also increase dehydration (Mayo Clinic).

3. Anyone who’s sick: fever, vomiting or diarrhea

With a fever, you lose extra water through your skin; Prof. Pokotylo estimates you need about 3–⁠10 fl oz (100–⁠300 mL) more a day for every 1.8 °F (1 °C) of fever. With vomiting or diarrhea, you lose minerals as well as water. The CDC advises drinking plenty of liquids and notes that over-the-counter oral rehydration solutions are most helpful for mild dehydration, while sports drinks may not replace the minerals you’ve lost. Watch children closely: a dehydrated child may cry with few or no tears and be unusually sleepy or fussy. If someone seems severely dehydrated, call your doctor.

Life stages that change your needs

4. Pregnant and breastfeeding women

Water aids digestion, helps form the amniotic fluid around the baby and helps nutrients circulate, ACOG explains, recommending 8–⁠12 cups (64–⁠96 fl oz) of water a day during pregnancy. The National Academies set total water at about 101 fl oz (3.0 L) a day in pregnancy, including about 10 cups from drinks, and 128 fl oz (3.8 L) while breastfeeding, including about 13 cups. Prof. Pokotylo gives the same ballpark: at least 10 glasses of fluid a day in both cases.

The FDA recommends asking your health care provider whether you need to limit caffeine while pregnant or breastfeeding. And check with your doctor before adding anything new to your routine, hydrogen water included.

5. Children and teens

Babies and kids carry a larger share of water in their bodies than adults (USGS), and busy kids easily forget to drink. In a study of 58 sixth-graders in a desert town, more than half arrived at school already dehydrated, and the well-hydrated children tended to score better on tests by midday (Bar-David et al., 2005). In another, children aged 7–⁠9 who were given extra water did better on attention tasks (Edmonds & Burford, 2009). Prof. Pokotylo’s advice: a water bottle always at hand, a few sips — about 2–⁠3 fl oz (50–⁠100 mL) — every hour or at breaks during school, and a glass before sports.

How much? The National Academies’ daily adequate intakes:

From age 9, the lower figure is for girls and the higher for boys. Babies are different: in their first 6 months, they don’t need water in addition to breast milk or formula unless a pediatrician says so. Around 6 months, you can start offering small amounts, about 4–⁠8 fl oz a day, the American Academy of Pediatrics advises.

6. Older adults

With age, thirst fades: older people feel less thirsty when they’re short on water, a pattern reported consistently for decades (Begg, 2017), and the kidneys become less able to conserve it. That’s why the National Academies set the same intake for adults over 50 as for younger adults — about 125 fl oz (3.7 L) for men and 91 fl oz (2.7 L) for women — instead of basing it on the smaller amounts older people usually drink. European geriatric guidelines advise offering older women at least 54 fl oz (1.6 L) of drinks a day and older men at least 68 fl oz (2.0 L), unless a medical condition calls for a different approach (ESPEN).

The practical takeaway: drink on a schedule, not on thirst. The National Institute on Aging suggests a simple check — drink enough that you need to urinate every few hours. In a heat wave, drink more than usual; if your doctor limits your fluids or you take water pills, ask how much to drink when it’s hot (CDC).

Habits that crowd water out

7. Coffee and tea lovers

Prof. Pokotylo’s rule of thumb is a glass of water with every cup of coffee, the way many cafés serve espresso. Newer research is more relaxed about coffee itself: in habitual coffee drinkers, four cups a day hydrated as well as the same amount of water (Killer et al., 2014), and US experts count caffeinated drinks toward your daily fluids. The rule still earns its keep, though, because coffee and tea can quietly replace water altogether. Keep plain water at least half of what you drink, as Prof. Pokotylo advises, and caffeine within about 400 mg a day — two to three 12-oz cups of coffee (FDA).

8. People watching their weight — and their skin

Water has no calories, so swapping sugary drinks for plain water is one of the simplest ways to cut calories, the CDC notes. A glass before meals may help, too: in a 12-week trial of 48 adults aged 55–⁠75 on a low-calorie diet, those who drank about 17 fl oz (500 mL) of water before each meal lost about 4.4 lb (2 kg) more than those on the diet alone (Dennis et al., 2010). Prof. Pokotylo adds a trick for snack cravings: the brain’s hunger and thirst centers sit side by side, so a sudden urge to snack is often thirst in disguise. Try a glass of water first.

And skin? “How much water do you drink during the day?” is the first question a good cosmetologist asks, Prof. Pokotylo notes. The research is modest. In 49 young women, adding about 68 fl oz (2 L) of water a day for a month improved measures of skin hydration, most of all in those who drank little to begin with (Palma et al., 2015). A systematic review rated the evidence as weak but found a slight rise in skin hydration with extra water (Akdeniz et al., 2018).

Who should be careful about drinking more

More water isn’t the right advice for everyone:

• People with heart or kidney disease. Some people need to drink less because of conditions such as kidney failure or heart disease, the National Institute on Aging notes. Your doctor sets the number.
• People who take water pills. Ask your doctor how much to drink, especially in hot weather (CDC).
• Endurance athletes. Drinking far more than you sweat can drop blood sodium dangerously low (hyponatremia). At the 2002 Boston Marathon, 13% of the runners tested at the finish had it (Almond et al., 2005). Drink to replace what you lose, not as much as you can.
• Babies under 6 months. Extra water can upset their mineral balance; stick to breast milk or formula unless your pediatrician advises otherwise (AAP).

Easy ways to drink enough

• Keep water where you are. Carrying a reusable bottle is the CDC’s first tip. The Living Aqua Insulated Bottle comes in 32 oz for the whole day and 22 oz for a bag or the gym, and it’s leak-proof.
• Drink on a schedule, especially for kids and older adults: a glass on waking, one before each meal and a few sips every hour.
• Make water the easy choice at home. A Living Aqua Hydrogen-Rich Alkaline Water Pitcher on the counter holds 3.8 L (128 oz) and turns tap water into filtered, hydrogen-rich water in about 2 minutes. Change the filter every 6–⁠8 weeks; spare filters are sold separately.
• Take it with you. If your water is already safe to drink, Living Aqua Hydrogen Water Discs turn a bottle of it into hydrogen water in 5 minutes.
• Pair every coffee with a glass of water.

If you’re pregnant, nursing or managing a health condition, check with your doctor before switching to hydrogen water. New to it? Start with What is hydrogen water.