15 Aug 2018 Water: More is NOT Better

The recommendation to drink more water is probably the most common and universally agreed upon advice given in the health industry, maybe second only to the suggestion to avoid sugar.

Most everybody has heard that they should start their day with a big glass of water and drink 8 glasses of water a day, and others even suggest that this isn’t enough. Some recommend drinking as much as ½ or even 1 oz of water per pound of bodyweight (this would be 18 glasses of water per day for someone weighing 150 lbs.)

And why wouldn’t we drink that much water?

Water is the essence of life. It has no calories and makes up as much as 60% of our body weight. Plus, it keeps us full so we eat less while also keeping our skin moisturized, wrinkle-free, and glowing. Oh, and did I mention it increases our metabolism too?

Better get chugging…

Yes, that was sarcasm. But it’s allowed because I believed all those things at one point too. For years I was known for never being seen without a water bottle and for getting multiple water refills whenever I was out to eat. I was always drinking water.

But, the dogmatic belief that drinking more water is better for our health is almost entirely unfounded, and most of the research actually points in the opposite direction.

 

The “Benefits” of Drinking More Water

It’s important to first acknowledge that water is not benign. While those that recommend drinking more water often recognize the dangers of dehydration, they ignore the dangers of overhydration. Overhydration can cause many of the same effects as dehydration, including headaches, impaired cognitive function, and even death.

I’ll explain exactly why overhydration is so dangerous in a little bit, but let’s first break down the supposed benefits of drinking water.

First is that water keeps us fuller, causing us to eat less, and has no calories, making it a healthy replacement for beverages that do contain calories. And this is at least somewhat true – drinking more water can make us eat slightly less (1, 2, 3).

But, as you may have read in several of my previous articles, eating less is NOT the answer for fat loss or improved health, and instead leads to stress and degeneration. And, the idea that having calories makes something less healthy is based on the heavily flawed calories-in/calories-out equation, which I described in this article.

The second supposed benefit is that water “increases our metabolism.” Again, this isn’t entirely untrue, as drinking water has been shown to increase energy expenditure by a small amount (around 24 calories per 500 mL) (4). But, this doesn’t mean that it improves metabolic function, will lead to fat loss, or that it’s even beneficial at all. In fact, this increase in energy expenditure is a sign of stress, which I’ll explain further in a little bit.

Third is the assumption that drinking more water increases hydration. Much of the advice to drink more water is based on the idea that dehydration is bad, so drinking water must be good. But, while dehydration is a legitimate issue (although not a very common one), simply drinking lots of water isn’t the best way to solve it.

In order for our cells to use water, they require minerals like sodium, potassium, and magnesium, as well as energy. Water is typically devoid of all those things, so drinking water won’t necessarily increase hydration and can even reduce cellular hydration because it lacks those other important nutrients.

Water is purported to have many other benefits, like relieving headaches and constipation. However, drinking water only helps these symptoms if dehydration was the cause of these symptoms, which often isn’t the case (5, 6). And, if these symptoms weren’t caused by dehydration, drinking water can make them even worse.

Other supposed benefits of drinking lots of water, like “flushing out toxins” and “boosting our immune system,” are mostly fabricated ideas that are, at best, based on a heavily flawed understanding of these features of physiology.

 

Water and Stress

There’s one major problem that comes with drinking lots of water. It’s actually the same issue that causes the extreme effects of overhydration, like headaches, impaired cognitive function, and death, although on a smaller scale.

And that problem is that it dilutes our blood, which reduces the concentration of various electrolytes, most importantly sodium.

The sodium level in our blood is tightly regulated. And, when it drops too low, our body’s stress systems are activated (7, 8). This leads to the production of stress hormones like aldosterone, which cause our bodies to retain more sodium (and excrete less) in order to increase the sodium concentration.

But, retaining sodium comes at a cost – the sodium we would normally excrete in our kidneys is replaced with potassium and magnesium, leading to the loss of greater amounts of these minerals (9).

A lack of potassium and magnesium, as well as the stress hormones themselves, then leads to cell swelling (10, 11, 12, 13). This swelling inhibits our ability to produce and use energy, which is disastrous for every aspect of our health (14).

I explain the cascade of events involved in this adaptive process more thoroughly in this article on salt consumption, but to summarize, a lowered sodium concentration in the blood (either due to drinking too much water or consuming too little sodium), can be extremely stressful on our bodies and has many negative consequences.

And, this is seen quite clearly in the research showing that drinking water increases energy expenditure (these are the studies often cited for water’s ability to “increase our metabolism”).

These studies have shown that this increase in energy expenditure is directly caused by the stress that results from a lowered sodium concentration in the blood (15, 16). This finding has been corroborated by several studies showing that drinking plain water leads to stress but drinking water with enough salt to mimic our normal blood sodium concentrations doesn’t (16, 17, 18, 19).

In other words, forcing ourselves to drink excess water can lead to stress and cell swelling, which negatively affects metabolic function.

But, as I’ll explain in a second, while drinking too much water can be harmful, we don’t have to worry much about it if we simply listen to our body’s innate signals that tell us how much we need to drink.

 

Thirst Has Got You Covered

The moral of the story is that more water is not better. So, there’s no need to force ourselves to drink a certain amount of water each day, which can be far more harmful than helpful. Instead, our bodies have their own hydration sensors that tell us when and how much we need to drink, so we can simply drink when we’re thirsty!

There’s a common myth that by the time you’re feeling thirsty you’re already dehydrated, but this is simply unsupported, as is explained in this quote:

“It is often stated in the lay press (17, 19, 22, 26) and even in professional journals (47) that by the time a person is thirsty that person is already dehydrated. In a number of scientific treatises on thirst, one finds no such assertion (1, 12, 30, 67, 69, 76, 98). On the contrary, a rise in plasma osmolality of less than 2% can elicit thirst, whereas most experts would define dehydration as beginning when a person has lost 3% or more of body weight (96), which translates into a rise in plasma osmolality of at least 5%.” (20)

And, as stated in these quotes, our sense of thirst is extremely sensitive, and it wouldn’t make sense biologically if we had to force ourselves to drink more water than we naturally wanted to just to remain hydrated:

“To prevent dehydration reptiles, birds, vertebrates, and all land animals have evolved an exquisitely sensitive network of physiological controls to maintain body water and fluid intake by thirst.” (6)

“Osmotic regulation of vasopressin secretion and thirst is so sensitive, quick, and accurate (67) that it is hard to imagine that evolutionary development left us with a chronic water deficit that has to be compensated by forcing fluid intake.” (20)

[Note: there’s also a common myth that if your pee isn’t clear you’re dehydrated, but this simply isn’t true (20).]

So, it’s quite clear that by using our sense of thirst, our body’s built-in hydration indicator, we can remain adequately hydrated.

 

Why Water?

There’s no need to limit our beverages to only water. There are tons of other options that come with added nutrients and taste better.

Fruit juice, milk, and tea or coffee with honey or sugar are all great options. These options have nutrients that allow us to produce energy and minerals needed for effective hydration, which water doesn’t have. (If you’re worried about the sugar in these drinks, check out these articles.)

Of course, this doesn’t mean that we need to avoid water, just that other drinks can be even better. And, if we’re drinking more water because we’re sweating a lot or for some other reason, it’s important to make sure we’re also getting enough sodium and other minerals to effectively rehydrate.

 

Just to hammer the point home, forcing ourselves to drink more water is not beneficial for our health, as is commonly suggested. Rather, we can rely on our sense of thirst to keep us hydrated, and we can also choose drinks other than water that contain the nutrients we need to produce energy and keep our cells hydrated.

 

References