Has Your Hydration Been Hijacked?

Jillian Mooney
January 30, 2024

When did ‘hydration’ become the latest status symbol?

When did carrying around huge water bottles or the latest 40 or 48 oz Stanley mug become a thing?

When did we start obsessing about drinking litres upon litres a day?

And if you’re an athlete, have you ever been more concerned with electrolytes?

The marketers have done a brilliant job at selling, but is it based on healthy hydration?

I don’t think so.

It’s high time we took the simple and critical act of hydration back.

But to do that, we’re going to have to start with some necessary vocabulary – baroreceptors, transporters, milliosmoles and pressure gradients.

It sounds complicated but it’s not. Trust me.

Read on…

Water pumps up the volume

We have to consume a certain amount of water to survive.

It forms the basis of blood plasma that transports nutrients, oxygen, hormones, antibodies, and pretty much everything we need to our tissues.

It also picks up the stuff we don’t need. Stuff that is eliminated through urine, poop, respiration and sweat.

Fluids that act as shock absorbers for our brain, spinal cord and organs are water based.

Our brain is 80% water.

It lubricates our joints.

It regulates our internal body temperature by sweating and respiration. A critical function for athletes and anyone exposed to high temperatures, an increasing part of life on earth.

Water provides the medium and volume we need for all of the above and more.

When we lose volume we lose efficiency, performance and function, and we risk illness and injury.

The difference between men and women

For adult men, 60% of the body is water.

For women, it’s 55%.

Men tend to have more muscle mass, which stores more water. This is why they can afford to lose up to 3-4% of their body weight through sweat or illness before health or performance is affected.

For adult women, our bodies store less water, because we typically have less muscle and more fatty tissue. Fat is anhydrous, it doesn’t store water.

We only have to lose 1-2% body weight before health or performance is affected.

Can you drink too much?

Yes, and it’s quite easy to do, especially given the big marketing push to drink, drink, drink!

Some start the day by chugging a big glass of water. Some folks walk around with huge water bottles or the latest Stanley mug overflowing with fluid and I bet their urine is clear but there is also a good chance they are dehydrated.

A lot of fluid at once or a significant amount over the day causes a volume response through something called baroreceptors – these are mechanoreceptors in blood vessels that register volume changes.

Remember, the body holds a certain fluid volume so understandably it is sensitive to fluctuations.

When you take in a lot of fluid, baroreceptors get triggered, send signals to your bladder to pee and you lose it all.

There’s also a condition called hyponatremia that is caused by drinking too much water, overdiluting the blood and upsetting the balance of minerals, primarily sodium.

It can be fatal and more than a few marathon runners and extreme athletes have suffered its consequences. Every year people die because of it.

It’s an extreme example but my point is this – urine can be completely clear because it can be extremely dilute.

Dilute urine is the very opposite of hydration.

Rule #1 – you can only call yourself hydrated when the fluid volume, within your body, is sufficient to continue all the functions outlined previously.

How does water get into the bloodstream?

Ninety-five percent of all fluid absorption occurs in the upper part of the small intestine.

This area is sensitive to fluid and the pressure changes that occur when ‘stuff’ is added to that fluid.

Stuff like electrolytes or carbohydrate (glucose, fructose, sucrose).

Remember, your blood plasma is also full of ‘stuff’- nutrients, oxygen, glucose, etc.

Blood plasma pressure is measured in milliosmoles and is tightly controlled between 275 and 295 mOsm.

The reason I’m telling you this is that absorption works along a pressure gradient – from low pressure to high pressure.

That means that the fluid you drink should always have a lower pressure than your blood plasma.

(ps: water will always have a lower pressure than blood plasma, just be cognisant of volume.)

If that’s the case, your small intestine will happily let that fluid in.

If, however, the pressure in your small intestine is higher than the pressure in your blood plasma nothing moves. In fact, fluid from your blood plasma and other spaces has to flow backwards into your small intestine to dilute contents and lower the pressure.

This is what is commonly known as sloshy gut. Many athletes will know what I mean.

It feels exactly as it sounds by the way and while that fluid is sloshing around in your gut, you are getting more and more dehydrated.

Hydration Helpers

Transporters are molecular workhorses when it comes to hydration. They literally ferry water through the wall of the small intestine, when the pressure gradient grants them access.

Sodium is the primary transporter and it works best in the presence of glucose.

The amounts of sodium and glucose are critical.

More isn’t better, despite what the marketers of sports and many hydration drinks might tell you. Remember our pressure gradient is sensitive.

It only takes around 5-9g glucose with a tiny pinch of salt (which is roughly 0.1-0.2g sodium) per 250ml ( a standard glass size).

So, if you have a concern around hydration – maybe you’ve sweat a lot, maybe a bout of vomiting, maybe your elderly parent or child has been exposed to heat – then you need a low sugar solution with a little added salt.

It can be as simple as a diluted fruit juice or fruit cordial. Check the label to make sure there’s a little salt and if not, add a tiny pinch.

This will hydrate significantly faster than plain water.

Specific Electrolyte powders and sports drinks

There’s good, there’s bad and there’s a whole lot of ugly.

But by now you are armed with the knowledge that effective hydration is all about pressure gradients and transporters.

You know you need 5-9g glucose, with a pinch of salt (0.2g sodium), per 250ml.

The more ‘stuff’ that gets added, the greater the potential to upset the pressure gradient.

I’ve seen single serving electrolyte sticks at 1g salt. Too much ‘stuff’.

I’ve seen no-sugar electrolyte drinks. Not enough ‘stuff’

I’ve seen drinks sold under the guise of ‘hydration’ that deliver sugar in the region of 20-30g plus 0.5g sodium in 250ml. Way, way, way too much ‘stuff’

And then there’s thoughtful products that combine 5-9g glucose and 0.2g salt in a single serving, just mix in a glass of water. The right amount of ‘stuff’.

A special note to athletes, especially the endurance kind – I know you have questions on how to balance carbohydrate drinks as fuel and electrolyte replenishment due to sweat loss. That is a topic deserves a blog of its own.

Stay tuned, that will be up next.

Guidelines to take back the simple act of hydration

I am not going to ‘market’ an arbitrary amount of fluid intake per day because it is entirely dependent on circumstance, activity level and environment. But if you start the day with pale yellow urine that’s a good sign.

If you focus on sipping water (remember those baroreceptors) or very dilute juice you are off to a great start. And water is a good choice, just manage your intake.

If you lose fluid via sweat or illness, you obviously need to account for that.

If you eat watery vegetables, fruits, drink tea, coffee (yes, that still counts as fluid) most of us will easily get in over 2 litres per day. You should account for fluid in foods and all drinks, not just pure water.

If you sprinkle a tiny pinch of salt on your salad or over veggies, that will enhance hydration from those sources.

And have some simple hydration products around for hot days, intense workouts or bouts of sickness. You can rely on products like Hydralyte, SOS Hydration, Nuun Hydration to do the job effectively or make your own.

My personal go-to? A splash of Miwadi (orange & pineapple) and a tiny pinch of salt in a standard glass.

Yes – it’s that simple.

I’m Jill – your food and hydration-friendly nutrition coach and I like to keep things simple and science based.

If you’re interested in cutting through the marketing noise and getting some practical and personal guidance on the way to reaching your goals – let’s connect.