Hydration matters for your lungs because your airways are lined with a thin layer of fluid and mucus that traps inhaled particles and is swept out by tiny hairs called cilia, and how well that mucus moves depends heavily on how hydrated it is [1][2]. In a small 2021 study, mild dehydration from exercise in the heat or a day without fluids slightly reduced lung-function measurements in healthy adults, and drinking fluids brought them back to normal [4]. Drinking enough every day is a simple way to support normal lung function.
Key Takeaways
- Your airways are lined by a mucus layer resting on a watery "brush" around the cilia. Mucus clears best when it is properly hydrated.
- In 10 healthy adults, losing about 2.5% of body weight through sweat or fluid restriction lowered forced vital capacity by about 150 mL; drinking fluids reversed it, but inhaling a saline mist did not.
- Breathing large volumes of dry or cold air during hard exercise draws water from the airway surface itself, separate from how much you drink.
- Adults need roughly 2.7 to 3.7 liters of total water a day from food and drinks combined. There is no official "8 glasses" rule.
- Drink when you are thirsty and with meals, and add more in hot weather, during exercise and when you are unwell. Follow your doctor's advice if you have been told to limit fluids.
Evidence grade: Emerging. How airway mucus depends on hydration is well established in physiology research, but human studies linking how much you drink to lung function are few and small: one controlled study of 10 adults and one study of 100 cyclists without a control group.
How Your Airways Use Water
Every breath brings in dust, microbes and other particles. The lungs' main mechanical defense is mucus clearance: a sticky mucus layer catches particles, and beating cilia, along with airflow and coughing, move it up and out of the airways [1].
Researchers describe the airway surface as a "gel-on-brush" system. The mucus gel sits on top of a dense periciliary layer, a brush of tethered molecules surrounding the cilia. This brush keeps mucus from sinking down onto the cells and lets it form a distinct layer that the cilia can move [2]. How fast mucus travels depends strongly on how concentrated it is: well-hydrated mucus moves, while mucus that holds too little water slows down [1].
The water that hydrates mucus does not come straight from the glass you drink. Airway cells move salt and water across their surface, balancing sodium absorption with chloride secretion, to keep mucus at the right hydration level in healthy lungs [1]. Your overall fluid status is part of the picture, as the studies below show, but local control by airway cells does most of the fine-tuning.
When airway mucus becomes too concentrated
In research on certain long-term lung conditions, such as cystic fibrosis and chronic bronchitis, mucus becomes too concentrated, or dehydrated. It then sticks to the airway surface and is cleared more slowly [1]. A 2015 study found that in people with chronic bronchitis, the more concentrated their mucus, the slower it was cleared from the lungs [3]. These changes come from altered salt and water transport in airway cells, not from drinking too little, and drinking more water has not been shown to correct them. Anyone with a lung condition should follow the treatment plan from their care team.
What Happens to Lung Function When You Are Dehydrated
A 2021 study in the Journal of Applied Physiology tested 10 healthy adults four times each: twice after 2 hours of exercise in the heat and twice after 28 hours without fluids. Both methods caused mild dehydration, about 2.5% to 2.7% of body weight [4].
When dehydrated, participants could breathe out about 150 mL less air in a full forceful breath (forced vital capacity), and more air stayed trapped in their lungs afterward. The changes pointed mainly to the small airways. Drinking fluids returned the measurements to normal. Breathing in a mist of salt water, which wets only the airway surface, did not [4]. The study was small and the changes were modest, but it suggests overall body hydration, not only airway moisture, affects how the lungs perform.
A 2023 study of 100 professional male cyclists found that lung-function measurements dropped after a hard exercise test. Cyclists with larger drops repeated the test 15 to 20 days later after following hydration instructions, and their drops were smaller [5]. The study had no control group, so other factors may have played a part. For more on fluids after training, see hydration and its role in recovery.
Breathing Dry Air During Exercise
During hard exercise you breathe large volumes of air, and your airways must warm and humidify all of it. As water evaporates from the airway surface liquid, that liquid becomes saltier, and water is drawn out of nearby cells [6]. In some people, this drying is thought to trigger the temporary airway narrowing that can follow vigorous exercise. Cold air makes it worse, because more of the airway has to be used to humidify it [6].
This is water lost from the airway surface during breathing, which is a different process from whole-body dehydration. The water you drink reaches the airway surface only indirectly, through airway cells [1], but staying hydrated before and during long sessions keeps your overall fluid balance steady. For training-day fluid plans, read our guide to hydration strategies for sports performance.
How Much Fluid Do You Need?
The Dietary Reference Intake for total water is about 2.7 to 3.7 liters (91 to 125 fluid ounces) a day for adults. That total includes water from food as well as all beverages [7]. Needs vary with sex, body size, age, activity level and health [7]. There is no specific recommendation for how much plain water to drink [7].
| Situation | What helps |
|---|---|
| Everyday life | Drink when you feel thirsty and have a beverage with meals; choose water over sweetened drinks [7]. |
| Older age | Thirst can fade with age, so drink fluids throughout the day rather than waiting to feel thirsty [7][8]. |
| Hot weather, exercise or outdoor work | Drink extra fluids. If you lose a lot of minerals in sweat, a sports or electrolyte drink can help; watch the sugar content [8]. |
| Illness with fever, vomiting or diarrhea | Get extra fluids. If liquids are hard to keep down, try small sips of water or ice chips [8]. |
| Fluid limits from your doctor | Follow your doctor's instructions rather than general guidelines. |
Water-rich foods such as soups, fruits and vegetables count toward your total, and so do milk, tea and coffee. Alcohol does not add to your body's water, because it makes you pass more urine [7].
Signs you may be low on fluids
In adults, common signs of dehydration include strong thirst, a dry mouth, urinating and sweating less than usual, dark urine, dry skin, tiredness and dizziness [8]. Get medical help right away if these come with confusion, fainting, no urination, a rapid heartbeat or rapid breathing [8].
What Research Does and Does Not Show
The physiology is clear: properly hydrated mucus clears better than concentrated mucus [1][2]. A small controlled study shows that mild whole-body dehydration can slightly reduce lung-function measurements in healthy people, and that drinking fluids reverses it [4].
Other common claims have weaker support. "Drink plenty of fluids" is standard advice for chest colds and other respiratory infections, but a Cochrane review found no randomized trials testing whether it helps. The authors noted that some observational studies suggest extra fluids could even cause harm in lower respiratory infections, because the body may hold on to more water during these illnesses [9]. That is why fluid advice during illness should come from your clinician. We found no good evidence that extra water strengthens immune defenses in the lungs or prevents long-term lung conditions, so those claims are not repeated here.
For more everyday choices people make with their lungs in mind, see our article on foods to avoid for better lung health.
Where an Electrolyte Drink Fits
For most people on most days, water and food cover fluid needs. On hot days, during long workouts or when you sweat heavily, MedlinePlus notes that a drink with electrolytes can help replace minerals lost in sweat [8]. OPA ION+ Select Electrolyte is a scoop-and-mix powder made to support daily hydration. It contains magnesium (as di-magnesium malate), potassium (as potassium chloride), sodium from Himalayan pink salt and vitamin B12 (as methylcobalamin), along with coconut water, beet root juice and acerola juice powders. It has no added sugars or stimulants and offers 30 servings per container.
To be clear: no study has tested this product, or electrolyte powders in general, for lung function. It is a convenient way to replace fluid and minerals on active days, not a lung supplement. Check the label for its sodium and potassium amounts if you watch either one.
Safety and Interactions
- Fluid limits: Some people are told by their doctor to limit fluids. If that applies to you, follow their instructions over any general guideline.
- Sweetened drinks: Some sports drinks contain a lot of sugar, so do not rely on them for everyday hydration [8].
- Potassium in electrolyte products: ACE inhibitors such as benazepril, angiotensin receptor blockers such as losartan, and potassium-sparing diuretics such as spironolactone reduce how much potassium the body excretes and can raise blood potassium [10]. If you take one of these or have kidney concerns, talk to your doctor or pharmacist before using an electrolyte supplement.
- Magnesium in electrolyte products: Count it toward the 350 mg daily upper limit for magnesium from supplements, and space it from bisphosphonates and certain antibiotics as your pharmacist advises [11].
- Breathing changes: Shortness of breath, wheezing or a cough that lasts are reasons to see a clinician, not to simply drink more water.
Frequently Asked Questions
Why is hydration important for lung function?
Your airways rely on a hydrated mucus layer to trap particles and move them out of the lungs, and mucus clears more slowly when it holds too little water [1]. In a small study, mild dehydration also slightly reduced lung-function measurements, which returned to normal after drinking fluids [4].
How does dehydration affect breathing?
In healthy adults who lost about 2.5% of their body weight in fluid, forced vital capacity fell by about 150 mL and more air stayed in the lungs after breathing out, mainly reflecting changes in the small airways [4]. The changes were modest and reversed after drinking fluids.
Does drinking water thin mucus?
It has not been shown directly. Airway cells control mucus hydration mainly by moving salt and water locally [1]. Staying hydrated supports normal fluid balance, but there is no trial showing that extra water thins mucus in healthy people.
How much water should I drink to support healthy lungs?
There is no lung-specific amount. Adults need about 2.7 to 3.7 liters of total water a day from food and drinks, and drinking when thirsty and with meals usually covers it [7]. Drink more in heat, during exercise and when unwell.
Do foods and other drinks count toward hydration?
Yes. Water-rich foods, soups, milk, tea and coffee all count toward your daily total. Alcohol does not, because it increases urine output [7].
Should I drink extra fluids when I'm sick?
Extra fluids help replace what you lose through fever, vomiting or diarrhea [8]. However, no randomized trials have tested whether drinking more shortens respiratory illnesses, and some observational data suggest too much fluid may not be helpful in certain chest illnesses [9]. Ask your clinician what is right for you.
Sources
- Hill DB, Button B, Rubinstein M, Boucher RC. Physiology and pathophysiology of human airway mucus. Physiol Rev. 2022.
- Button B, Cai LH, Ehre C, et al. A periciliary brush promotes the lung health by separating the mucus layer from airway epithelia. Science. 2012.
- Anderson WH, Coakley RD, Button B, et al. The relationship of mucus concentration (hydration) to mucus osmotic pressure and transport in chronic bronchitis. Am J Respir Crit Care Med. 2015.
- Marshall H, Gibson OR, Romer LM, et al. Systemic but not local rehydration restores dehydration-induced changes in pulmonary function in healthy adults. J Appl Physiol. 2021.
- Pigakis KM, Stavrou VT, Pantazopoulos I, et al. Effect of hydration on pulmonary function and development of exercise-induced bronchoconstriction among professional male cyclists. Adv Respir Med. 2023.
- Anderson SD, Daviskas E. The mechanism of exercise-induced asthma is ... J Allergy Clin Immunol. 2000.
- MedlinePlus Medical Encyclopedia. Water in diet. U.S. National Library of Medicine.
- MedlinePlus. Dehydration. U.S. National Library of Medicine.
- Guppy MP, Mickan SM, Del Mar CB, et al. Advising patients to increase fluid intake for treating acute respiratory infections. Cochrane Database Syst Rev. 2011.
- NIH Office of Dietary Supplements. Potassium: Fact Sheet for Health Professionals.
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals.
Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.
Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: · How OPA researches and writes
