What do humans need to drink?

December 20, 2025 •

4 min read

The human body is composed of 50 to 75% water, with this vital liquid forming the basis of blood, digestive juices, and other fluids. To maintain these crucial functions and prevent dehydration, humans need to drink a sufficient variety of fluids, with water being the most essential.

Quick Summary

Optimal hydration is vital for human health, with plain water being the best fluid source. Other beverages and water-rich foods also contribute to daily intake, which varies based on individual factors like activity level and environment.

Key Points

Water is Essential: Water is the most vital fluid for human health, supporting critical bodily functions like temperature regulation and waste removal.
Needs are Individual: Daily fluid requirements vary based on factors like age, sex, activity level, and environment, so listen to your body's cues.
Beyond Plain Water: Healthy alternatives like milk, herbal tea, and fruit-infused water can supplement your intake and provide additional nutrients.
Avoid Sugary Drinks: High-sugar beverages like soda and sweetened juices can be detrimental to health and should be limited.
Recognize Dehydration Signs: Be aware of symptoms like thirst, dark urine, headaches, and fatigue, and increase fluid intake immediately.
Hydrate Throughout the Day: Instead of chugging large amounts at once, drink fluids gradually throughout the day to maintain optimal hydration.

The Core Role of Water in Body Function

Water is not just a thirst-quencher; it is a vital nutrient critical for almost every bodily process. It plays a central role in maintaining overall health by serving multiple essential functions:

Regulates body temperature: The body uses water through sweat to prevent overheating, especially during exercise or in hot climates.
Lubricates and cushions joints: Water helps protect sensitive tissues and serves as a shock absorber in the spinal cord and eyes.
Eliminates waste: Fluid is necessary for flushing out toxins and metabolic by-products through urination, perspiration, and bowel movements.
Aids digestion: Proper hydration helps break down food and absorb nutrients more effectively.
Transports nutrients and oxygen: Water keeps the bloodstream fluid, allowing it to carry vital nutrients and oxygen to every cell.

Establishing Your Daily Fluid Needs

While the conventional wisdom of drinking eight glasses of water a day is a reasonable goal, individual fluid needs vary significantly. Factors such as your age, sex, activity level, health status, and environment all influence how much you should drink. The U.S. National Academies of Sciences, Engineering, and Medicine provide a helpful baseline for total daily fluid intake, which includes fluids from all beverages and foods:

Men: Approximately 15.5 cups (3.7 liters) per day.
Women: Approximately 11.5 cups (2.7 liters) per day.
Pregnant and breastfeeding women: Require additional fluids to support their and their baby's needs.

Around 20% of your daily fluid intake comes from foods, especially water-rich fruits and vegetables, leaving the rest to be supplied by beverages.

Beyond Plain Water: Other Hydrating Options

While water is the ideal choice for hydration, other beverages can contribute to your daily fluid intake, and some offer additional nutritional benefits.

Healthy Choices

Milk (Dairy and Plant-Based): Milk is about 90% water and provides essential nutrients like calcium, protein, and vitamin D. Unsweetened plant-based milks, such as soy or almond, can also be a good option.
Fruit-Infused Water: For those who dislike the taste of plain water, infusing it with slices of lemon, lime, cucumber, or berries adds flavor without sugar.
Herbal Tea: Caffeine-free herbal teas are a hydrating, antioxidant-rich alternative to water.
Coconut Water: This natural drink is high in water content and provides electrolytes, making it a good choice for rehydration.

Less Ideal Options

Sugary Drinks: Beverages like soda, sweetened fruit juice, and energy drinks are loaded with added sugar and calories, which can lead to weight gain, inflammation, and other health issues.
Excess Caffeine: While moderate caffeine intake is not significantly dehydrating, excessive amounts can cause jitters and interfere with sleep.
Alcohol: Alcoholic beverages, particularly hard liquor, have a diuretic effect that can lead to rapid dehydration.

Comparison of Hydrating Beverages


Beverage Category	Hydration Efficacy	Nutritional Value	Considerations
Plain Water	Excellent	None (calorie-free)	Best all-around choice; readily available and free.
Milk (Dairy/Plant)	Excellent	High in calcium, protein, and Vitamin D (dairy).	Offers nutrients and hydration. Choose low-fat or unsweetened varieties.
Infused Water	Excellent	Minimal (from fruit/herbs)	Flavorful alternative for those who find plain water boring.
Sports Drinks	Good (for intense exercise)	Contains electrolytes and carbohydrates.	High in sugar; only necessary for prolonged, high-intensity activity.
Fruit Juice	Good (but with caution)	Vitamins and minerals.	High in natural sugars; should be consumed in moderation, or diluted.
Caffeinated Beverages	Moderate	Antioxidants (tea/coffee).	Can have diuretic effects in large quantities; can affect sleep.
Sugary Sodas	Poor	Little to none	High in calories and sugar; can cause weight gain and health problems.
Alcohol	Poor	Minimal	Causes dehydration; should be consumed in moderation.

Recognizing and Preventing Dehydration

Dehydration occurs when your body lacks enough fluids to function properly. While mild dehydration can often be treated by simply increasing fluid intake, severe cases require medical attention.

Signs of Mild to Moderate Dehydration

Thirst
Dry or sticky mouth
Infrequent urination
Dark-colored urine
Headache
Muscle cramps
Fatigue

Signs of Severe Dehydration

Very dry skin
Rapid heartbeat and breathing
Sunken eyes
Dizziness or confusion
Listlessness or irritability

To prevent dehydration, it is crucial to drink fluids throughout the day and listen to your body's thirst signals. In addition to beverages, consuming water-rich foods like salads, fruits, and soups can help. For more comprehensive information on healthy eating, Harvard Health Publishing offers a wealth of resources on nutrition and diet.

Conclusion: Making Hydration a Priority

For humans, drinking enough fluid is not optional; it is fundamental to health. While water is undoubtedly the best choice, other healthy beverages and foods can contribute to your daily needs. By paying attention to your body's signals and incorporating healthy hydration habits into your routine, you can support every vital function, from digestion and circulation to mood and energy levels.

Frequently Asked Questions

While it varies, the U.S. National Academies of Sciences, Engineering, and Medicine recommend approximately 15.5 cups (3.7 liters) of total fluids a day for men and 11.5 cups (2.7 liters) for women, which includes fluids from all foods and beverages.

Yes, caffeinated beverages like coffee and tea contribute to your overall daily fluid intake. However, it's best to consume them in moderation, as high amounts of caffeine can have diuretic effects on some individuals.

Common signs of dehydration include thirst, a dry or sticky mouth, infrequent or dark-colored urine, headaches, and feeling tired or dizzy.

For most people, water is the best choice. Sports drinks are high in sugar and are primarily recommended for high-intensity, prolonged exercise lasting more than an hour, where electrolytes are lost through sweat.

Yes, about 20% of your daily water intake comes from solid foods, especially those with high water content like fruits and vegetables.

Drinking excessive amounts of water in a short period can lead to a rare condition called hyponatremia, or water intoxication, which causes sodium levels in the blood to drop dangerously low.

You can add natural flavor by infusing water with slices of lemon, lime, cucumber, or berries. Carrying a reusable water bottle can also serve as a helpful reminder to drink regularly.