Why Drinking Too Much Water Could Be Harmful: A Dietitian's Expert Advice

Many people grow up believing that drinking a lot of water is always good for the body. We’re constantly reminded to “stay hydrated,” and while that advice holds a lot of truth, a lesser-known fact is that excessive water consumption can also be dangerous. In a world where health and wellness trends often encourage more of everything — more vitamins, more detoxing, more hydration — it becomes easy to assume that water is one of those “more-is-better” substances. However, just like anything else, water must be consumed in moderation. A registered dietitian, Mrs. Oludayo Coates, has raised an important point on this subject. Speaking from her wealth of experience as the Head of the Dietetics and Nutrition Department at Alimosho General Hospital in Lagos, Mrs. Coates cautioned against drinking water excessively, explaining that it could lead to serious health issues — some even life-threatening.

Contrary to the common assumption that water is always harmless, Mrs. Coates explained that when consumed in extreme quantities, water can disrupt the body's natural balance of electrolytes, especially sodium. This disruption can result in a dangerous condition known as hyponatremia. Hyponatremia occurs when there is an excessive amount of water in the body compared to the level of sodium, which is a critical electrolyte needed for many bodily functions. In this state, the sodium levels in the blood become dangerously diluted, which can cause swelling in cells, including brain cells. As the brain swells, the affected individual may begin to experience symptoms like confusion, nausea, vomiting, headaches, fatigue, and in more severe cases, seizures, coma, or even death. This is why moderation is important, even when it comes to something as essential as water.

Mrs. Coates emphasized that many people do not believe water can be harmful because of its reputation as a "life-giving" substance. Indeed, water is essential to human survival. It is involved in countless processes within the body: it regulates temperature, aids digestion, transports nutrients, removes waste, cushions joints, and protects organs. No one is denying the vital role of water. However, the issue lies in how much water is being consumed. Drinking too much water in a short period can overwhelm the kidneys, which are responsible for filtering water and electrolytes from the bloodstream. When the kidneys can no longer keep up with the excessive intake, the excess water stays in the bloodstream and enters cells, leading to swelling and pressure.

Aside from hyponatremia, drinking too much water can also lead to other discomforts and symptoms. Mrs. Coates pointed out that it may cause a bloated stomach, vomiting, muscle pain or weakness, and drowsiness. In some people, especially those who already have underlying health issues such as kidney disorders or hormonal imbalances, these symptoms may escalate more quickly. For individuals who regularly work out or perform physically demanding tasks, drinking too much water without replacing lost sodium and other electrolytes (through food or supplements) can also be risky. Water intoxication, though rare, is not a myth. It has been documented in various medical journals, often occurring in athletes or individuals who, after extended exercise or sweating, drink large quantities of plain water without any salt replacement.

Still, Mrs. Coates was clear to point out that this doesn’t mean people should stop drinking water or reduce it to dangerously low levels. Instead, the message is one of balance. “Too much of everything is harmful,” she said. This principle applies to food, medication, and even exercise — and it certainly applies to water. She advised people to listen to their bodies and drink according to their individual needs. The sensation of thirst is a natural signal from the body that it needs more fluids. Ignoring thirst is not healthy, but neither is forcing water into the body beyond what it needs.

She referenced guidelines from the National Academy of Science and General Medicine, which recommend a daily intake of about 3.7 litres of water for men and 2.7 litres for women. That translates to approximately 13 cups for men and 9 cups for women, per day. However, even these recommendations are based on average body sizes, climates, and levels of activity. A person who lives in a hot environment and sweats a lot might need more water. On the other hand, someone living in a cold climate and not moving much may need less. Therefore, these numbers serve only as a general guide and should not be treated as one-size-fits-all rules.

Dehydration — the opposite of overhydration — also carries its own risks and should not be ignored. Mrs. Coates warned that inadequate water intake can lead to dehydration, which often begins subtly. Signs of dehydration include dry mouth, dark-colored urine, fatigue, dizziness, and headaches. As dehydration progresses, it can lead to dry coughs, rapid heartbeat, and in more severe or prolonged cases, urinary tract infections (UTIs), kidney stones, or even kidney failure. This is especially dangerous for older adults, children, and people who are sick, as their bodies may not give clear or strong signals of thirst. Dehydration can also affect concentration, mood, and physical performance, even before more serious symptoms appear.

One interesting point made by Mrs. Coates was that hydration needs vary depending on factors such as weather conditions, body size, lifestyle, and the nature of one’s job. For instance, a construction worker in the sun will naturally need more fluids than an office worker in an air-conditioned space. Likewise, a person doing high-intensity workouts will need more water than someone spending the day sitting at home. Even diet plays a role: people who eat lots of fruits and vegetables, which have high water content, may not need to drink as much as those who consume drier, saltier foods.

Mrs. Coates suggested a practical approach: drink when you are thirsty and at regular intervals during the day. Avoid extremes — don’t wait until you feel dizzy and dehydrated, but also don’t chug down litres of water in a short time “just to stay hydrated.” She also advised people to observe their urine color as a simple indicator. Pale yellow urine usually suggests proper hydration, while very dark or amber-colored urine may be a sign of dehydration. On the flip side, completely clear urine all day may suggest overhydration.

Furthermore, she emphasized the importance of access to clean, potable water. Water must not only be consumed in the right amounts but also be safe and free from harmful microbes or contaminants. Access to clean water is a public health priority and a human right. It affects everything from sanitation and food production to disease prevention. The United Nations has also highlighted that water plays a critical role in sustainable socio-economic development, energy generation, and ecosystem health. Poor water quality can lead to diseases such as cholera, diarrhea, and other serious infections.

Mrs. Coates' advice comes at a time when many people are taking more interest in health, fitness, and nutrition — and are often influenced by popular trends on social media. While the intentions are good, misinformation can easily spread when people follow advice that lacks scientific backing. One such trend is the “gallon of water a day” challenge, which has been popular in fitness communities. While this may work for some individuals, it’s not safe or necessary for everyone. Forcing yourself to meet a random water goal every day can cause unnecessary strain on the kidneys and lead to the exact issues Mrs. Coates warned about.

This is why nutritionists, dietitians, and healthcare professionals always advocate for personalized health advice. What works for one person may not work for another. Instead of following general fads, it’s better to understand your own body and consult professionals when needed. Mrs. Coates encouraged people to develop a healthy relationship with food and hydration — one that’s guided by science, moderation, and awareness, rather than pressure or misinformation.

In conclusion, water is absolutely vital to our health, but just like anything else, it must be consumed wisely. Too little water, and you risk dehydration and all the health problems that come with it. Too much water, and you could suffer from hyponatremia or other complications. The body is designed to maintain a delicate balance, and the best thing you can do is support it by paying attention to your natural thirst cues, adjusting your intake based on your environment and activity, and always making sure your water is clean and safe to drink. With the right mindset and a balanced approach, water will continue to serve its purpose as one of nature’s greatest gifts to our survival and well-being.