A reader recently wrote to me to ask what kind of drinking water I recommend. That exchange reminded me that we’re exposed to a fair bit of misleading information about what we should be drinking. With that in mind, let’s look at the key questions I get about our fluid intake and the best evidence we have to guide our consumption of water and other liquids.
What patients most commonly want to know is how much water they should be drinking. According to the Institute of Medicine’s (IOM) dietary reference intakes, the “vast majority” of us stay properly hydrated by letting our thirst guide us. Still, the IOM provides a recommended amount of total daily water intake: an average of 3.2 litres/quarts (3.7 for men, 2.7 for women). Given that food provides approximately 20% of our needs we should target 2.5 litres of drinkable fluids, which works out to 10 glasses of 8 oz. (250 ml).
However, if we are sweating from exertion or heat, or if we are ill with vomiting and/or diarrhea, we need to increase our liquid intake. And if our fluid losses are unusually high, we also need to replace the sodium, potassium and chloride that leave our bodies along with water. In those circumstances, “sports drinks” that include these elements would be the best liquid to consume.
But since we rarely need our water to be mixed with other nutrients we should take a closer look at what makes for the best drinking water.
The first consideration is safety. That means assuring that the water we drink is free of disease-producing germs, harmful chemicals and radiation by monitoring all waters’ source and distribution. For water that’s treated before distribution, that process must be checked too. Monitoring responsibility depends on whether the drinking water comes from a tap or from a bottle; tap water comes under environmental regulation whereas bottled water is regulated as a food.
But just because drinking water meets safety requirements doesn’t mean that it will be free of qualities that can make it unappealing: we expect our water to be transparent, free of odour and have desirable taste. Taste is the most subjective of these, which is why people vary in their preference between bottled products, or the tap water of one locale compared to another.
Taste is also the main reason for people to use water filters. Whether in the form of a carafe/jug system, a tap attachment or a system installed under a sink, filters can improve the taste of household tap water. A filter may also reduce amounts of harmful germs and chemicals, particularly in water from wells (we consider what remains after municipal water treatment to be safe for consumption).
Note that treating our drinking water isn’t limited to removing things from it: many water systems add fluoride to water to protect our teeth from cavities. In fact, the .US Centers for Disease Control and Prevention listed water fluoridation as one of the ten great public health achievements of the 20th century.
But despite its good work there is small minority of citizens who believe that water fluoridation is unsafe. Ignore their claims: adding fluoride to water to reach internationally agreed levels is based on sound research.
Of course, the question about which drinking water is best has to include mention of bottled water. A triumph of marketing over science, there is no evidence that bottled water offers any benefit over tap water; in fact, a good portion of bottled water is simply tap water that has been filtered and put in a container with inviting images and soothing text.
To put it simply, bottling water creates needless cost, packaging and shipping, which makes it one of the most wasteful “innovations” that the food industry has ever developed. When it comes to drinking water, save your money and save the planet by sticking with what comes out of your tap, using a filter if you prefer.
Finally, patients still regularly ask me about two other liquids strongly promoted for their health benefits: milk and juice.
With respect to milk and other dairy products, their most distinctive nutrient is calcium. But we can get that from meat, fish and a variety of vegetables. And while milk is often fortified with Vitamin D there are easy alternatives to that too (see the previous post ‘Tis the season to think about Vitamin D supplementation). Many people never consume dairy and almost none of them suffer adverse health effects.
As for juice, it’s an extract from fruits or vegetables. While you can find some very enthusiastic endorsements of juice (including yet other products from the soft drink industry) the fact remains that juicing separates sugar and flavour from nutrients and dietary fibre. In that respect it’s somewhat like refining whole grain – not something that’s desirable.
That means that drinking water from our taps – safe, plentiful, calorie-free and cheap – should be our beverage of choice.