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Why Drinking 8 Glasses of Water a Day is a Myth

Have you ever heard of the 8x8 rule? Well, it simply states that everyone should drink eight 8-ounce glasses of water daily. That’s no less than 2 liters.

The thing is — many people have come to accept this rule. But the question is “is the 8x8 rule backed by scientific evidence or is it just another myth?”

Read on to find out.

What’s the origin of the 8 glasses of water per day rule?

The origin of this rule has not been confirmed. Some sources say that it originated way back in 1945 when a group of researchers suggested that the average individual needs to drink 1 ml of water per calorie of food consumed.

So, that means a person consuming 2000 calories had to drink 2000 ml of water (or eight oz glasses).

However, the researchers also hinted that a great percentage of this amount could be obtained from the food consumed.

Dr. Frederick Stare also contributed to the 8x8 rule. His book published in 1975 recommended that the average individual drinks 6–8 glasses of water daily.

He also pointed out in his book that vegetables and fruits contained lots of water.

The bad news, however, is that this part of the story was left out when the research report was disseminated to health organizations and the public.

What does the research say about the 8 glasses of water per day rule?

A 2002 study examined the evidence behind the 8 glasses of water per day rule.

The study reviewed tons of surveys, studies, and articles, and could not find any scientific evidence suggesting that one must drink 8-oz glasses of water daily for adequate water intake.

It is however important to note that this finding is limited to healthy adults, especially those leading sedentary lives and in mild climates.

Agreed, some conditions may require that one increase their water intake, but then, people that are generally healthy don’t have to drink such large quantities of water.

It is also important to note that not taking enough water may trigger mild dehydration. A person is said to be mildly dehydrated when he or she loses 1–2% of body weight due to loss of fluid. Mild dehydration may cause headaches, fatigue, and mood impairment.

Do you constantly eat food even though you’re not hungry?

But one can avoid mild dehydration without necessarily following the 8x8 rule. Nature has given us a regulatory mechanism called thirst. When you are thirsty, it means that your body needs water. So, your water intake should be determined by thirst.

Is there anything wrong with drinking plenty of water?

The truth is that drinking water in excess can cause dehydration. The excess water destabilizes the balance between electrolytes, minerals, and water in your body. It is also important to note that there are electrolytes in your urine. So, the frequent peeing will cause you to lose some minerals and electrolytes. In many cases, it gets worse.

Drinking lots of water can dilute the sodium in your body. When the sodium is diluted, it can no longer regulate the quantity of water absorbed by the cells. This condition is called hyponatremia.

Body cells that are deprived of sodium usually swell up, triggering a barrage of symptoms ranging from headaches and confusion to coma. In extreme cases, the affected individual may die.

You don’t only need water to stay hydrated

Your body gets water from different sources and not just the plain water that you drink. Your body also gets hydrated from other beverages like juice and milk.

What’s more? Mild alcoholic drinks and caffeinated beverages are also fluid sources, especially when you take them in moderation. However, if you take these beverages in excess, they become diuretics. A diuretic is a substance that stimulates fluid loss by causing you to pee frequently.

Eating water-rich foods also supplies your body with a lot of water. Vegetables and fruits are classic examples of water-rich foods. Eggs, fish, and meat also contain plenty of water.

Finally, your body produces water within itself when it metabolizes nutrients. Water produced in this way is known as metabolic water.

So, drink water when you’re thirsty. Focus on increasing your electrolytes by eating plenty of vegetables such as a salad at every meal.


  1. Armstrong, L. E., Ganio, M. S., Casa, D. J., Lee, E. C., McDermott, B. P., Klau, J. F., Jimenez, L., Le Bellego, L., Chevillotte, E., & Lieberman, H. R. (2012). Mild dehydration affects mood in healthy young women. The Journal of nutrition142(2), 382–388.https://doi.org/10.3945/jn.111.142000
  2. Ganio, M. S., Armstrong, L. E., Casa, D. J., McDermott, B. P., Lee, E. C., Yamamoto, L. M., Marzano, S., Lopez, R. M., Jimenez, L., Le Bellego, L., Chevillotte, E., & Lieberman, H. R. (2011). Mild dehydration impairs cognitive performance and mood of men. The British journal of nutrition106(10), 1535–1543.https://doi.org/10.1017/S0007114511002005
  3. Valtin H. (2002). “Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8 x 8”? American journal of physiology. Regulatory, integrative and comparative physiology283(5), R993–R1004. https://doi.org/10.1152/ajpregu.00365.2002

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