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By Tim H. Tanaka, Ph.D., Director

When to Drink or Not Drink Water

In the August 2009 issue of Pacific Wellness Quarterly, I addressed the potential health issues that can arise from drinking too much water.

I stated that the oft-repeated guideline “eight glasses of water a day” should not be applied uniformly; rather, the recommendation should be adjusted on an individual basis.  I can obtain a fairly good sense of a patient’s hydration status by examining his or her skin, face, legs, and tongue and asking a few questions, including the color of the patient’s urine.  In my opinion, despite the commonly held belief to the contrary, chronic systemic dehydration is rather rare in Canada except in cases in which a patient is taking certain medications or on recreational drugs.  I doubt that most of us really need to (or even should) sip water all day, as some health practitioners recommend unless we are in direct sun or performing rigorous physical activity.  Thus, I generally recommend that individual drink water only when he or she feels thirsty.  There are, however, a couple of important time periods to keep in mind regarding water consumption.

  • We lose quite a bit of body fluid while in bed; therefore, many people are dehydrated upon awakening, as evidenced by darker-colored urine for most people.  Early-morning dehydration is particularly pronounced for people who tend to sweat at night.  Night sweating is common among premenopausal women, as well as people who eat late at night or over-consume alcohol, caffeine, or spicy foods.  As well, individuals who tend to sleep with their mouths open are more likely to lose extra water during sleep via mouth breathing.  It is, therefore, a good idea to drink a glass of water upon awakening.  As I explained previously using the example of watering a tree , our cells are hydrated most efficiently when our bodies are slightly dehydrated.
  • On the other hand, it is important not to drink large amounts of liquids just before and during meals. A commonly suggested reason for this is that it can dilute the stomach acids and enzymes required for the proper digestion of food.  While that is certainly true, there is another possible factor to be considered: one study suggested that drinking 500ml of water in a sitting could induce activation of the sympathetic nervous system within 10 minutes and that the effect can last for more than an hour.1  The sympathetic nervous system is a part of the autonomic nervous system, which is activated with physical activity and emotional stress.  It is associated with the fight-or-flight response (the so-called “adrenaline rush”)—a situation in which the body shuts down digestion and elimination activities to conserve energy.  So drinking water before meals not only materially dilutes digestive acids and enzymes but may also suppress the actual secretion of gastric juices.  Please note that the magnitude of sympathetic activation through water drinking is not extreme, as it is during the fight-or-flight response. Still, it is far preferable that the other part of the autonomic nervous system, the parasympathetic nerve (associated with relaxation), be dominantly aroused during mealtime.  The parasympathetic system triggers the secretion of stomach acid and digestive enzymes and enhances the motility of the digestive tract.

Water Temperature

Though it was not necessarily the case historically in many regions of the world, almost all of us who live in modern cities today can obtain fresh water virtually everywhere at any time, thanks to contemporary sanitation infrastructure developments and the ubiquitous presence of convenience stores.  In addition, we can obtain fresh beverages that are nicely chilled.  It is important to keep in mind that cold beverages, including cold water, chilled beer, and soda pop served in ice-filled glasses, have been conveniently available only in recent decades since the invention of freezers and refrigerators.  In traditional East Asian medicine, it has long been believed that our digestive tracts should not be cooled down, regardless of each person’s constitution (i.e., whether he or she is a hot or cold type).  I do not think our bodies have adapted to handle large quantities of cold drinks and frozen desserts.  It is, therefore, best to drink water at room temperature.

The Importance of Considering the Quality of Water Intake

I think the media and health advocates have too broadly emphasized the importance of drinking more water in recent years. Adequate water intake is essential for our health.  However, it is important to consider not only the quantity but also the quality of water intake, which includes water temperature and the timing of consumption.


A 2002 study published in the American Journal of Physiology questioned the old recommendation of 8 ounces of water, eight times a day. After a thorough review, researcher Heinz Valtin concluded there was inadequate evidence that healthy adults — living in temperate climates and not engaged in rigorous activities — need large amounts of water.

For normal, healthy adults, Valtin recommended simply drinking when thirsty. And he reported that even caffeinated drinks can count toward satisfying our fluid requirements.

In February 2004, the Institute of Medicine (IOM) issued new recommendations that agree with Valtin’s findings. The new guidelines remove the eight-glasses-a-day recommendation and say healthy adults may use a thirst to determine their fluid needs. Exceptions to this rule include anyone with a medical condition requiring fluid control; athletes; and people taking part in prolonged physical activities or whose living conditions are extreme.