What Would Happen if I Drink Milk Instead of Water?

December 5, 2025 •

4 min read

While milk is approximately 90% water, replacing your total daily fluid intake with it would drastically increase your caloric consumption and lead to a host of health problems. This article explores exactly what would happen if you drink milk instead of water for an extended period.

Quick Summary

Replacing water with milk would cause a massive increase in caloric and saturated fat intake, leading to significant weight gain, digestive issues, and nutrient imbalances like iron deficiency anemia.

Key Points

Significant Weight Gain: Consuming the necessary fluid volume from milk instead of water would lead to a massive increase in daily caloric intake, causing rapid weight gain.
Digestive Problems: Large quantities of milk can overwhelm the digestive system, leading to bloating, cramps, and other gastrointestinal distress, especially for those with lactose intolerance.
Nutrient Imbalance: Over-reliance on milk displaces other food sources, resulting in deficiencies (like iron) and excess intake of calcium and fat, stressing the kidneys and heart.
Inferior Everyday Hydration: While milk retains fluids longer post-exercise, water is the best and most neutral option for general, daily hydration needs.
Increased Health Risks: Excessive and sustained milk consumption increases the risk of chronic issues like iron deficiency anemia, kidney stones, and heart disease from saturated fat.
Impractical and Expensive: Replacing water with milk is economically unfeasible due to cost and logistical challenges like constant refrigeration.

Short-Term Effects of Replacing Water with Milk

If you were to completely replace your water intake with milk, the initial effects would be surprisingly fast and noticeable. The human body is not designed to process such a rich liquid in the quantities needed for proper hydration, which typically amounts to several liters a day. The result is a cascade of immediate consequences that affect your digestive system and overall well-being.

Digestive Distress

Unlike plain water, milk contains lactose, fat, and protein that require more effort to digest. Consuming large volumes would likely overwhelm your system, leading to uncomfortable and consistent digestive issues, even if you are not lactose intolerant. Common symptoms would include:

Bloating and abdominal cramps
Diarrhea or constipation
Increased gas

For the millions who are lactose intolerant, the effects would be far more severe, with symptoms manifesting much more quickly and intensely.

Caloric and Saturated Fat Overload

One of the most significant changes would be the dramatic increase in your daily caloric intake. A cup of whole milk contains about 150 calories, meaning that replacing a recommended 8 glasses of water (approx. 2 liters) with milk would add about 1,200 calories to your diet per day. Without a corresponding reduction in food intake, this would lead to rapid and significant weight gain. The saturated fat in whole milk would also substantially increase, putting a strain on your cardiovascular system.

Long-Term Health Consequences

If the practice continued beyond a few days, the initial discomfort would evolve into more serious, chronic health problems. The body's reliance on a single, nutrient-dense source would create dangerous nutritional imbalances and put vital organs under extreme stress.

Iron Deficiency Anemia

Drinking large amounts of cow's milk can inhibit the absorption of iron from other foods due to its high calcium and casein content. This is a particular concern for children, but can affect adults as well. Iron deficiency anemia can lead to a host of symptoms, including fatigue, paleness, and shortness of breath. For toddlers, excessive milk consumption has been linked to severe anemia requiring medical intervention.

Kidney Stress and Mineral Build-Up

High calcium intake from excessive milk consumption forces the kidneys to work harder to filter out the mineral. Over time, this can lead to the formation of kidney stones and other serious renal issues. Water is essential for flushing toxins and waste from the body, a job milk is ill-equipped to handle due to its composition and density.

Cardiovascular Problems

As noted, excessive intake of saturated fats from milk can contribute to high cholesterol and increase the risk of heart disease. While some studies suggest a more neutral effect for moderate dairy consumption, replacing all water with full-fat milk would far exceed any recommended intake and likely have a detrimental impact on heart health.

Milk vs. Water for Hydration: A Detailed Comparison

While some studies have shown milk can be effective for rehydration, particularly after intense exercise, it is not a superior replacement for water in everyday situations. The key difference lies in the purpose and speed of fluid delivery and absorption.


Feature	Water	Milk
Caloric Content	0 calories	100+ calories per cup (varies by fat content)
Primary Function	Hydration, flushing toxins, metabolic processes	Nutrient delivery, bone health, muscle repair
Absorption Rate	Rapidly absorbed and utilized by the body	Slower absorption due to fat, protein, and sugar content
Nutrient Balance	Pure and neutral, allows for nutrient balance from food	High in calcium, fat, protein; can cause imbalances
Everyday Use	Ideal for daily, all-purpose hydration	Suitable in moderation or specific contexts like post-exercise

Other Considerations and Conclusion

Beyond the direct health impacts, a complete switch from water to milk has other impracticalities. The high cost of buying enough milk to sustain yourself, the need for refrigeration, and the overwhelming flavor profile make it an unsuitable long-term strategy. Milk is a valuable part of a balanced diet, offering essential nutrients like calcium, protein, and vitamin D. However, moderation is key. It is designed to be a component of nutrition, not the sole source of fluid. Your body needs the pure, neutral hydration that only water can provide to function properly. Therefore, while a glass of milk can supplement your fluid intake, especially after a workout, water must remain your primary source of hydration for optimal health and bodily function. The idea of replacing water completely is not only unrealistic but would lead to severe and potentially life-threatening health issues.

For more detailed nutritional information on dairy, you can consult resources like the Harvard T.H. Chan School of Public Health website.

Frequently Asked Questions

While milk can be hydrating, especially after intense exercise, it should not replace water for your general daily fluid intake. Its high calories, fat, and protein content are not suitable for all-purpose hydration.

Yes, you would likely gain a significant amount of weight. Replacing several glasses of zero-calorie water with high-calorie milk would dramatically increase your daily caloric intake, leading to weight gain.

Some studies suggest that milk may be more effective at maintaining fluid balance after a strenuous workout than plain water due to its protein, carbohydrates, and electrolytes, which slow down fluid loss.

Drinking excessive milk can cause digestive problems like bloating, cramps, and diarrhea, even in individuals who are not lactose intolerant. The high lactose and fat content can be difficult for the digestive system to process in large volumes.

Yes, excessive milk consumption can lead to health issues such as iron deficiency anemia (especially in children), weight gain, and an increased risk of kidney stones due to high calcium intake.

The primary difference is that water provides pure, zero-calorie hydration for essential bodily functions, while milk is a nutrient-dense food that provides calories, protein, fats, and minerals in addition to fluids.

No, it is not realistic. The high caloric density, cost, and digestive burden of drinking only milk make it an impractical and unhealthy strategy for long-term hydration.