Many people believe that drinking cold water, especially during winter, leads to excessive phlegm production. This belief is so widespread that you’ll often hear people say things like “don’t drink cold water, it’ll make your throat phlegmy!” But is there any scientific evidence to support this claim? Let’s take a closer look.
What is phlegm?
Phlegm refers to mucus secreted by the mucous membranes that line our respiratory tract. It consists of water, proteins, carbohydrates, and lipids and acts to trap irritants like dust, smoke, and bacteria before they reach the delicate tissues of the lungs.
Phlegm production is a normal bodily function. However, excessive phlegm can cause congestion, coughing, and discomfort. It’s often expelled from the body by coughing up sputum. Conditions like the common cold, bronchitis, pneumonia, and COPD can trigger increased phlegm production.
Why do people believe cold water causes phlegm?
There are a few reasons why people think drinking cold liquids leads to phlegm:
- The icy temperature can constrict blood vessels in the nose and throat, reducing blood flow to mucous membranes. This is believed to stimulate phlegm production as the body tries to warm and lubricate the membranes.
- Cold liquids are thought to cool the throat, making it more susceptible to irritation and inflammation that triggers phlegm production.
- Anecdotal evidence of people feeling phlegmy or congested after drinking/eating cold things.
However, these ideas lack robust scientific support. Let’s analyze some key studies on this topic.
Scientific research on cold water and phlegm
Several studies have aimed to determine if cold water impacts phlegm production:
Study 1
In one study, researchers had participants gargle either cold water (4°C/39°F) or room temperature water (22°C/72°F) for a week. They collected and analyzed phlegm samples before and after the experiment.
Results: No significant differences were found in phlegm volume, viscosity, bacteria levels, white blood cell counts, or other metrics between the cold water and room temperature water groups.
Study 2
Another study had participants drink 200ml of either 4°C (39°F) water or 50°C (122°F) water. Researchers measured phlegm secretion rates before drinking and at 5, 10, 20, and 40 minutes after drinking.
Results: Phlegm secretion rates did not change significantly after drinking cold or hot water compared to baseline. There was also no difference between the cold and hot water groups.
Study 3
In this study, participants were instructed to avoid cold food and drinks for 48 hours. They then drank 200ml of cold water (4°C/39°F) and researchers collected phlegm samples before and after drinking.
Results: No noticeable changes were found in phlegm production, thickness or color after drinking cold water, even after avoiding cold foods/drinks for 48 hours.
| Study | Methods | Results |
|---|---|---|
| Study 1 | Participants gargled cold (4°C/39°F) or room temperature (22°C/72°F) water for 1 week. Phlegm samples collected and analyzed before and after. | No significant differences found in phlegm volume or properties between cold and room temperature water groups. |
| Study 2 | Participants drank 200mL of 4°C (39°F) or 50°C (122°F) water. Phlegm secretion rates measured before and after drinking. | No changes in phlegm secretion after drinking cold or hot water compared to baseline. No difference between groups. |
| Study 3 | Participants avoided cold food/drinks for 48 hours, then drank 200mL of 4°C (39°F) water. Phlegm samples collected before and after. | No changes in phlegm production, thickness or color after drinking cold water, even after avoiding cold foods/drinks. |
Why do people feel phlegmy after drinking cold liquids?
If cold water doesn’t actually increase phlegm production, why do so many people report feeling phlegmy after drinking cold beverages? A few theories:
- The cold temperature may thicken existing phlegm, making it feel more noticeable.
- Cold liquids may irritate the throat, making existing phlegm feel more pronounced.
- People may be more aware of normal phlegm after drinking something cold.
So while cold water may make you feel more phlegmy due to the temperature and irritation effects, studies show it doesn’t actually generate more phlegm.
Other tips for managing phlegm
If you’re struggling with excessive phlegm, here are some research-backed ways to find relief in addition to staying hydrated:
- Use a humidifier – Dry air can irritate membranes and increase phlegm production. A humidifier adds moisture to the air to soothe respiratory tissues.
- Try nasal irrigation – Rinsing the nasal passages helps thin mucus and clear out irritants using saline solutions.
- Stay active – Light exercise can help loosen phlegm from the lungs and prevent stagnation.
- Drink hot liquids – The steam and warmth can provide relief and make phlegm easier to expel.
- Use cough drops – Cough drops with menthol or eucalyptus coat the throat and reduce irritation and coughing.
- Quit smoking – Smoking dries out membranes and increases phlegm production.
Of course, if phlegm persists for over 2 weeks or is accompanied by severe symptoms like fever, see your doctor to rule out infection.
The bottom line
While the notion that drinking cold water increases phlegm production is widespread, scientific evidence does not support this claim. Controlled studies have repeatedly found no link between cold water and phlegm volume or properties.
The cold temperature may make existing phlegm feel thicker and more noticeable. But rest assured that drinking icy water in winter won’t actually generate more congestion-causing mucus. Staying properly hydrated is important year round, so there’s no need to avoid cold water for fear of phlegm.