Eight Glasses of Water Myth

The realization that most bits of conventional wisdom are wrong is one of the uncomfortable but empowering lessons of going on a skeptical journey to understand the world we live in. It is likely not true if you pick up knowledge from popular culture. Many reliable sources get tricked at times.

Right and wrong are not absolutes. Sometimes incorrect information can be oversimplified or lacking context. It is difficult to come up with a scientific question that can be used in a one-liners meme. Reality is much more complicated than you think.

There is a meme that says people should drink eight glasses of water a day. Although it is not completely benign, this piece of misinformation is a good example of why we should be skeptical of medical advice.

In 1945 the U.S. Food and Nutrition Board determined that an adult needs 84.5 ounces of water per day to remain healthy. This advice was distorted. Most of the water will come from food. Water comes from food. Most of the stuff we drink is water. Coffee is mostly water and won't make you sick because of the caffeine. The water intake is much larger than the effect.

The 84.5oz became 64 because it can be translated into the 88 rule, which means eight glasses of water. There is more than one layer. The bottled water industry promotes this myth. They promoted the myth because they have a vested interest in people drinking more of their product.

Despite the fact that it is widely discredited online, the 88 myth is still going strong. It is a popular myth to debunk. It continues to be widely spread. It is more complex than that.

There is no evidence for the recommendation of 8 glasses of water a day. It is not based on science. There is no evidence that following this rule will benefit you in the long run. Reality is far more complex than this recommendation suggests. hydration needs vary greatly from person to person. The amount of food consumed, the size of the person, the environment, and physical activity are some of the factors that affect them.

Basic understanding of human physiology is what led to this. There is empirical evidence to back this up. Water turnover is the amount of water people need from all sources. Their summary is here.

Water intake requirements largely reflect water turnover (WT), the water used by the body each day. We investigated the determinants of human WT in 5604 people from the ages of 8 days to 96 years from 23 countries using isotope-tracking (²H) methods. Age, body size, and composition were significantly associated with WT, as were physical activity, athletic status, pregnancy, socioeconomic status, and environmental characteristics (latitude, altitude, air temperature, and humidity). People who lived in countries with a low human development index (HDI) had higher WT than people in high-HDI countries.

We don't know how much water we need to stay hydrated. Over the course of hundreds of millions of years, evolution has been able to perfect a method called thirst. If you are thirsty, drink when you are thirsty. If you don't have access to fluid, you won't be able to drink when you need to. If you are going to be in a hot environment or in a dry environment, you need to be aware of this. When you are in environments that are not familiar to you, you can get dehydrated very quickly. There is no need to drink pure water. If you don't want to eat to replace electrolytes, you should drink electrolyte drinks. There are other sources of fluids that are okay.

People with certain medical conditions may need to limit their fluid intake or drink more water than usual. Keep your urine pale if you have a history of stones. Speak to your doctor if you have any questions.

Is it possible to overhydrate? It's hard to cause harm. It takes a lot of water to overwhelm your body's homeostatic mechanisms. It does happen. You might need to get up at night to urinate if you drink too much water. Chronically poor sleep has a lot of medical drawbacks. It is harmful for the environment to use a lot of plastic water bottles.

The greatest harm that I see in my practice is that people who want to live a healthy lifestyle are confused and distracted. Most of the time when a patient says to me that they are trying to lead a healthier lifestyle, they put together a list of things that are useless. Eight glasses of water is included in this list. They should focus on the things that will improve their health instead of being lulled into a false sense of health.

The myth fosters a simplistic understanding of human biology. It is difficult to measure the harm of things like that.

• Steven Novella is the founder and currently Executive Editor of Science-Based Medicine. The Great Courses and The Skeptics Guide to the Universe were both written by Dr. Novella.

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