Hi, my partner and I have recently started eating paleo...we are almost up to 3wks!
One thing we have both noticed is that we don't feel the need to drink as much water as we used to. We used to both regularly drink around 2 litres a day.
We have been tossing around possible reasons why...maybe eating more veges with a higher water content? Or, possibly less glucose dumping in urine so more water re-absorption in kidney tubules?
I am curious if anyone else experienced this or has any thoughts on why this might be the case?
Interesting observation, Crystal. Here are some possible explanations:
1) When you switch from SAD to paleo, your glycogen stores become less "tanked-up." Glycogen storage requires water, so now you need less water than previously.
2) You may have dropped some "cardio" from your workouts. Paleo workouts tend to be shorter and more intense. Shorter workouts means less sweating and lower water requirements.
3) Sometimes when you switch to paleo you don't get enough iodine. This can lower your thyroid function and make you feel colder. When you feel cold, you have peripheral vasoconstriction, which lowers anti-duiretic hormone (ADH) and raises atrial natiuretic peptide (ANP). This lowers your sensation of thirst ( http://www.unh.edu/inquiryjournal/06/articles/dinon.html ). Be sure you're taking enough iodine.
4) Loss of fat stores can also make you feel cooler (see #3 above). If you find yourself getting cold or chilled more easily, try eating a thermogenic food like coconut oil or coconut milk (high in MCTs).
5) I agree with you that eating high water content vegetables can reduce thirst.
I have experimented with three things and came up with these results:
I think it's due to the blood sugar stabilizing effect of the diet. A lower carb diet stabilizes blood sugar more. So does a higher protein diet.
However, I don't think it's because of the less glucose dumping in urine. I think your diet prevents hypoglycemia, and therefore lessens your secretion of cortisol during hypoglycemia.
As you know, cortisol is a stress hormone which has a diuretic effect. So the more hypoglycemic you are, the more cortisol you will produce to raise your blood sugar.
Additionally, a higher protein diet stabilizes your blood sugar swings because it stimulates the release of a hormone called glucagon when your blood sugar is low. So a higher protein diet will prevent hypoglycemia, therefore decreasing cortisol secretion during hypoglycemia.
Fructose also stabilizes blood sugar by stimulating glucagon when your blood sugar is low, just like protein. (I eat up to 100 grams of fructose per day from sweet potatoes and fruit!)
Cortisol, by itself, is diuretic. So reducing cortisol by controlling your hypoglycemic episodes lessens water loss. In addition, cortisol causes sodium retention and potassium loss within the small intestine. So less cortisol further prevents water loss because it balances your electrolytes.
I experience the same. My glycogen stores are most likely fine. I still eat fruit. And I have not dropped any cardio because I was never a big fan in the first place. Actually, cardio never made me thirsty because I did it in the air conditioned gym and did not sweat much.
I suspect the issue is at least partly because grains require a lot of water to digest. The body breaks down the starch into its constituent parts via hydrolysis, ie the addition of water to break up the starch molecules. The water molecules are incorporated into the new smaller molecules.
For most of us, I don't think it has anything to do with loss of sugars pulling water out via urination. Healthy people do not have spilling of glucose into urine. If you are not diabetic, this should not be happening. But if you are diabetic, I am sure that would part of it.
HOwever, there are probably other issues that we don't fully understand yet. Water is used in all body functioning. I am not surprised that the body might need more water when dealing with greater strain on the system.
I noticed the same thing since going Paleo. I hardly drink any water at all during the day now, usually just a few sips when I wake up and here and there it seems. Interestingly, ate dinner with some family last week, very non-paleo of course, several wheat products including a little bit of pasta--I was absolutely astonished at how unbelievably thirsty I was for the rest of the day, I was guzzling water like you would not believe, it was horrible.
Just throwing another thought out there: I've noticed that on paleo I drink less in between meals, but still have a lot of water with meals. (I'm just obeying my thirst, and that's what it tells me to do.) So maybe it seems like you're drinking less overall just because you're not drinking as frequently.
Not doubting your own account of your water consumption, of course. It could be a mixture of what I'm suggesting plus one or several of the things from what everyone else has suggested in their answers. Such that there might be an overall decrease in water intake, plus a decrease in frequency of intake, which then makes the overall intake seem like less, "phenomenologically."
Anyhow this happened to me I'm pretty sure.
For me I have noticed that I go to the toilet less now that my insulin levels are lower. When I have food that trigger an insulin response ( Like cream ) I need to urinate almost straight away. So I wonder if we are not triggering insulin - we are weeing less and therefore needing less water to drink???
I don't have any data to support this theory but I do have to wonder - I definitely only urinate or defecate after an insulin response ( most people do - think about it next time you go to the toilet - what did you do or eat before hand ? Exercise and nervousness both trigger it also as they evoke insulin response)
Food ( low carb no less ) for thought!