Is it bad to drink milk when it's hot? The science behind temperature and digestion

November 5, 2025 •

4 min read

Despite a long-standing myth, dietitians note that milk, even cold, is actually an excellent hydrating choice during hot weather because of its high electrolyte content. So, is it bad to drink milk when it's hot? Not at all, but the effects on your body, including digestion and sleep, differ based on temperature and your individual needs.

Quick Summary

This article explores how drinking milk at different temperatures affects digestion and hydration. It covers the contrasting benefits of warm and cold milk, debunking common myths about consuming milk during hot weather.

Key Points

Not Bad to Drink: It is not harmful to drink milk when it's hot, assuming the milk is properly pasteurized and handled.
Hydration Benefits: Milk is an excellent hydrating beverage for hot weather or after exercise due to its high electrolyte content, often outperforming water.
Digestion Differs: Warm milk digests faster and can be more soothing for sensitive stomachs, while cold milk can provide quick relief from acidity.
Nutrient Impact: Excessive boiling can reduce levels of heat-sensitive nutrients like B vitamins, but pasteurized milk's core nutritional value is stable at a normal warm temperature.
Choice is Personal: The ideal temperature for consuming milk depends on your individual health needs and preference, whether for soothing comfort or cooling relief.
Debunking Myths: The idea that milk is a 'bad choice' in the heat is a misconception; its natural components are highly beneficial.
Listen to Your Body: Pay attention to how your body responds to different temperatures of milk and choose what feels best for your digestion and comfort.

The Core Question: Is Milk Safe in the Heat?

For centuries, people in various cultures have held different beliefs about the effects of consuming warm and cold beverages, particularly milk. The core of the issue isn't safety—pasteurized milk is safe regardless of temperature—but rather the physiological impact it has on the body, especially in hot conditions. A glass of milk, hot or cold, remains a nutritious source of protein, calcium, and vitamins, with its fundamental nutritional value largely unchanged by moderate heating. The key difference lies in how your body processes and responds to the temperature.

How Temperature Affects Digestion

One of the most significant differences between drinking hot and cold milk is the rate of digestion. A 2024 study conducted by Teagasc used Magnetic Resonance Imaging (MRI) to monitor the digestion process in a lab setting. This research found that the proteins in warm milk coagulate faster in the stomach than those in cold milk.

Warm Milk for Soothing Digestion

For many, especially those with sensitive stomachs or mild lactose intolerance, warm milk can be a more comfortable option.

Faster Coagulation: The faster protein coagulation in warm milk can lead to a more efficient and gentler digestive process for some individuals.
Relaxation: Warm beverages have a soothing effect that helps relax the digestive tract, which can alleviate symptoms like bloating and discomfort.
Psychological Comfort: The warmth itself can trigger a calming response, reducing stress that might exacerbate gastrointestinal issues.

Cold Milk and Acidity

Conversely, cold milk is often recommended for soothing stomach acid.

Reduces Acidity: Cold milk provides temporary relief from heartburn and acidity by neutralizing excess stomach acid.
Electrolyte Replenishment: After a workout or on a very hot day, cold milk is an excellent way to replenish electrolytes lost through sweat, aiding in hydration.

Milk and Hydration: A Heatwave Secret Weapon

Contrary to the famous quote in Anchorman, milk is not a 'bad choice' in a heatwave; in fact, it is a highly effective hydrator. A study from St Andrews University found that both skimmed and full-fat milk can be more hydrating than plain water after exercise due to their rich content of electrolytes, protein, and carbohydrates. The sodium and potassium in milk help the body retain fluids for longer periods, making it a surprisingly effective beverage for combating dehydration during hot weather or strenuous activity.

Nutritional Considerations of Heating Milk

While moderate heating doesn't significantly alter milk's overall nutritional profile, prolonged boiling can impact certain heat-sensitive nutrients.

Vitamin Reduction: Boiling milk can reduce the levels of B vitamins (like B6, B12, and folate) and vitamin C, which are sensitive to heat. One study found that boiling milk reduced its B vitamin content by approximately 25%.
Protein Structure: Heating causes slight protein denaturation. While this can aid digestion for some, it doesn't represent a major nutritional loss.
Safety vs. Nutrition: For regions without consistent refrigeration, boiling milk is a safety practice to kill bacteria. However, for pasteurized, refrigerated milk, this isn't necessary and can slightly diminish nutritional value.

Comparison: Hot vs. Cold Milk


Feature	Hot Milk	Cold Milk
Digestion	Easier for sensitive stomachs, coagulates faster.	Can be harder to digest for some; provides quicker relief from acidity.
Acidity Relief	Mild relief from soothing effect.	Quick and effective relief due to neutralizing effect.
Hydration	Still hydrating, but the warmth may be less refreshing in heat.	More refreshing and potentially more appealing in hot weather; highly effective at rehydrating.
Sleep Aid	Promotes sleep by releasing tryptophan, serotonin, and melatonin.	No direct sleep-aid benefits beyond psychological.
Nutrients	May have slightly reduced levels of some heat-sensitive vitamins if boiled for too long.	Retains full vitamin and mineral content.
Comfort	Soothing and calming effect; good for cold weather or bedtime.	Refreshing and cooling effect; excellent for summer or post-exercise.

Conclusion: Personal Preference and Context are Key

So, is it bad to drink milk when it's hot? The simple answer is no. Modern, pasteurized milk is safe to consume hot or cold, and in fact, its rich electrolyte content makes it a superior hydrator to water during hot weather. The decision of whether to drink hot or cold milk ultimately comes down to personal preference and your specific health goals. If you are seeking a calming bedtime drink or have a sensitive stomach, a warm glass might be more suitable. If you need a refreshing, hydrating boost after a workout in the sun, cold milk is the optimal choice. Both provide the same essential nutrition, though prolonged boiling should be avoided to preserve maximum vitamin content. The key is to listen to your body and enjoy milk in the form that best serves your needs.

For more in-depth nutritional information on dairy, you can consult resources like The Dairy Alliance, which provides science-backed content on milk's benefits.

Frequently Asked Questions

No, drinking hot milk is not bad for digestion; in fact, the warmth can help relax the digestive tract and make the milk's proteins coagulate faster, which can be easier for some people to digest.

No, drinking milk in hot weather does not cause health problems. It is a very hydrating beverage, rich in electrolytes that help replenish fluids lost through sweat.

The best temperature depends on your needs. Warm milk can be more soothing and better for sleep, while cold milk is excellent for cooling down and relieving acidity.

While standard pasteurization does not harm nutrients, prolonged boiling can slightly reduce the levels of heat-sensitive vitamins like B vitamins. For already pasteurized milk, boiling is unnecessary and can diminish some nutritional value.

Research has shown that milk, particularly after exercise, can be more hydrating than water. This is because its electrolytes and protein content help your body retain fluids longer.

Yes, cold milk can provide temporary relief from heartburn and acidity by coating the stomach lining and neutralizing stomach acid.

Yes, warm milk can aid sleep. It contains tryptophan, an amino acid that helps produce sleep-inducing chemicals like serotonin and melatonin, promoting relaxation.

Heating milk does not eliminate lactose, so individuals with significant intolerance should stick to lactose-free options. However, some with mild sensitivity report fewer symptoms with warm milk compared to cold.