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Water and cold drink are NOT the same thing
Rehydrating with a cold drink, puts back the water, along with some sugar. The glucose is FUEL, but the fructose………is a challenge, for a dehydrated kidney.
It’s a stinking hot day………..
And you’ve been out and about, maybe you were doing something fun, maybe it’s duty.
You’re dehydrated.
To quench your thirst, you reach for an ice cold soda. It’s wet. It’s cold. It’s an energy boost.
A long hard swig, brings relief…..
You’re rehydrated and back to “normal”.
Maybe NOT !
It’s water PLUS fuel
Yes. You’ve put the water back, but in the process, you put in a mix of fructose and glucose. The glucose is body FUEL, but the fructose………well, it’s complicated.
Fructose is a natural sugar, but it’s naturally a little “unbalanced”, which makes it a bit more of a challenge to take up and use.
So the sudden arrival of large quantities of fructose, necessitates a little managing.
Managing the fructose
The posterior pituitary, steps up to the plate……….. squirting out vasopressin, the hormone in charge of osmolarity. While the enzyme fructokinase, ready’s himself, to mop up.
But in this scenario, there is a catch.
Vasopressin is already busy as a bee……… because, you’re dehydrated.
Oh well.
More of good thing, can’t be a bad thing. Right ?
Chronic kidney disease
Concerned, by the observation that more and more sugar cane workers, are succumbing to chronic kidney disease, because of recurrent dehydration, the team decided to “dig” a little deeper.
So they put some rats to work in “the fields”.
The little guys didn’t actually have to cut or chop, sugar cane, but they did get seriously HOT, for one hour a day, every week day. On Saturday and Sunday, they rested.
This simulated the dehydration, experienced by the sugar cane labourers.
Recovering from the heat
Following their “roasting”, the rats were given an opportunity to rehydrate, with a “special” beverage. The rats could drink as much, or as little as they liked, of this “special” beverage, for a two hour window.
- Some drank the equivalent of a coke (7.15% fructose and 3.85% glucose)
- Some drank tap water
- Some got a water, with a hint of sweet.
NOTE : The sweet used in this study was stevia. The reason for sweetening up the water, was to make it more palatable. Ensuring both sets of rats, consumed the same amount of water. Rats, just like humans, can turn up their nose to plane water.
Drinking their fill
The rats made merry until the next day – eating and drinking (water only) ad libitum i..e as much as they liked.
And then it was “hiho hiho, it’s off to work I go”.
4 weeks later…………the scientific investigations began in earnest.
Kidney vigour
Urine and blood was sampled, blood pressure was measured and then………………….
It was over.
The team carefully extracted the kidneys – to assess, what shape they were in.
A sorry site
Rehydrating with a soda, had put strain on the kidneys……..
Histology studies showed glomerular and tubular alterations.
Fructose and uric acid levels, were higher in the cortex of the kidney and the tissue was clearly experiencing more oxidative stress, when the animals had used coke” to rehydrate.
Markers of kidney “damage”. © 2016 the American Physiological Society
In contrast, when the animals had used plain water or the stevia flavoured water, to rehydrate, there were no deleterious effects.
Fructose is a problem
When you’re dehydrated………
The rats, using the soda to rehydrate, drank 12 ± 1.1 ml in the 2 hour window, this is not an excessive amount.
In fact, when the researchers allowed another group of rats, to work in “an office” for the month. Despite sipping on 14 ml of soda / day, these guys, had NO SIGN of kidney problems.
NOTE : The office job came with air conditioner.
So what’s the problem ?
Too much vasopressin for one.
The researchers confirmed vasopressin receptors were up-regulated in the kidneys.
Renal cortex vasopressin V1a and V2 receptors expressions in mildly dehydrated animals. © 2016 the American Physiological Society
The other problem………..TOO MUCH fructose.
Remember, I said, it’s hard to handle.
Handling fructose is a team effort
In fact, in an ideal situation, it should be handled by the small intestine, but when you swigged it down, without any food, the small intestine doesn’t get a chance to DO ANYTHING.
So, the handling falls on the shoulders of the other organs.
The liver, does his bit.
But, so does the kidney.,,,,
Fructokinase
Is located in the proximal tubule of kidney.
He takes care of the problem. But this is an energy drain.
It’s not a problem, if it happens every now and again. But if it happens habitually, this puts STRESS on the kidney.
And some kidneys just can’t cope with it…..
Protect you kidneys
So don’t put your kidneys at risk….
Rehydrate with water, and use those fructose based drinks as a treat.
NOTE : It is better to consume fructose based drinks as part of a meal. Click here to learn more.
Further reading
It’s official – too much fructose, whatever form it’s in, makes you fat
Small amounts of fructose aren’t a problem. In fact, they’re a treat, but large amounts of fructose are a metabolic CRISIS.
What happens when the fructose in your sugar treat, “gets” away
From your small intestine, because you ate too much, too quickly – your liver has to deal with it. Now, it can, but fructose is unbalanced, so it’s not easy
Fructose is a hangover cure for bats. And humans ?
Bats don’t have access to aspirin and silencing a thousand shrieking neighbours is not an option. So what does a bat do when it eats fermenting fruit ?