are you drinking enough water?

[dakotajudo]

You might want to back up a little bit here. A little knowledge is a dangerous thing.

I’m pretty sure this is beating a dead horse, but are you? Last week while I was at work I almost feinted after standing up (orthostatic hypotension; see 1), something that had previously not happened to me before.

Orthostatic hypotension is a condition of low blood pressure (20mm Hg or so) whilestanding, not upon standing. When you stand up, it takes a moment or so for cardiac output to compensate to the change in posture. While that's happening, you may get light headed - it's fairly normal.

If you remain standing and after a couple minutes you continue to feel light-headed , then you might consider orthostatic hyptension.

Thus, a diet of 2500 k/cal suggests about 2.5 L of water from both food and drink (most of your dietary water comes from the food you eat).

Not really - beverages account for most of the water. See http://www.jacn.org/cgi/content/full/22/2/165

Another important thing to note is its also what you drink and eat that’s important. ‘Salted’ drinks like soda require more water to deal with the excess salt.

I'm not so sure about this. High sodium diets tend to cause you to retain more water - this is why people with high blood presure go on low salt diets.

This goes double for caffeinated drinks like coffee and tea and those redbull-esque energy drinks as caffeine is a diuretic. Alcohol also has similar effects by inhibiting the production of vasopressin, a hormone used to conserve body water. The importance of reading labels and being aware of what’s inside goes without saying. For example, in coke products there is usually around 50mg of sodium as well as a small amount of caffeine. <3> Energy drinks usually are infused with as much caffeine as a cup of coffee (some in Japan have more).

The diuretic effects of caffiene aren't all that important - see, for example,
http://www.jacn.org/cgi/content/abst...e2=tf_ipsecsha
http://www.ncbi.nlm.nih.gov/entrez/q..._uids=15467100
http://www.ncbi.nlm.nih.gov/entrez/q..._uids=16131696

High protein diets especially have a higher requirement for water than their ordinary counterparts.

Not really, for reason given below.

This is primarily because while the excess protein is converted to either fat or sugar by the body,

What you're talking about is gluconeogenesis, which is really only important when your diet relies excessively on proteins. Excess amino acids are not obligated to be converted to carbon sources.

the extra urea produced by this conversion requires more water to excrete it as urine.

Not necessarily; the kidneys can adjust urine concentration to compensate for excess urea.

A recent study done at the University of Connecticut found that hydration needs increased as the amount of dietary protein increased. What’s more is that the participants in the study did not realize they were any thirstier than with their previous diet. <4 & 5>

This is a poor citation - you refere to unpublished result. The published version seems to suppport a different conclusion ( http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum) . From the abstract

The effect of increasing dietary protein on fluid status was minimal.

Note the dates as well.

For me, the 2L or so of water was fine before, but the extra protein I added in my diet changed my needs enough to create a potentially bad situation. I hope this was helpful for someone.

Instead of all this guesswork, you can do a simple measurement to see if you're dehydrated.

Weigh yourself. If you lost 3% bodyweight in short period, you may have become dehydrated. Otherwise probably not.

I've noticed I can drop three pounds in a two hour workout, and be back up by the next morning, with no ill effects that I can tell. Do you think your diet has caused as drastic a change?

The problem here is that this line of reasoning may account for an increase in hyponatremia among casual athletes. People become so worried about becoming dehydrated, during exercise, that they over-drink, and ultimately dilute themselves to death. See

http://www.pubmedcentral.nih.gov/art...medid=16816267
http://www.pubmedcentral.nih.gov/art...medid=16344476
(note the % weight loss in Fig 1).


In short, don't worry about it.

A couple other points.

I also heard that if you cut Gatorade with water (about 50 percent) then it is better for you.
Anyone know anytyhing about this?

Yeah, I've heard this too, but I think it only applies to drinking Gatorade during exercise - if you're on a long (1 hr +) ride or run, where glycogen depletion may be an issue with performance (otherwise, moderate water intake is fine).

My take is that it has to do with osmosis. Absorbing your drink passively, it needs to have a lower osmolar concentration than your tissues - water follows sugars and salts.

You will eventually absorb the solutes in the drink, but that requires active transport and may take longer.

If it's post-exercise, the concentration doesn't matter so much.

Orthostatic Hypertension... So thats what that is.... I suffer from this all the time...

Probably not O.H. - what's your resting heart rate?

If you're fit, you've become adapted to the sympathetic drive that occurs during exercise, and you may have lower sympathetic drive at rest. One symptom of this is low cardiac output, and a corresponding low heart rate.

Sympathetic output is largely responsible for adjusting cardiac output (thus blood pressure) when you change position. If you're adapted to exercise, your body might not respond to change in position as rapidly.

If you a napping on the couch, stand up and this happens, it's probably no big thing. If it happens during a workout, you might worry.

My take on temperature is room is best, because there are alot of functions that require a certain range of pH and that is affected by temperature. I dont really have anything right off the top of my head that say temp affects stomach acid, but it stands to reason.

You might want to rethink that. pH is only minimally affected by temperature; ezymatic reactions are going to be more affected. As for stomach acid, it doesn't have much effect on absorption, its role is primarily in providing a acid environment for stomach enzymes.

As for the temperature of a drink - you may drink it cold, but by the time it gets to actually being absorbed (at the cell surface), it's going to be pretty much body temperature, I'd think. The GI tract is prett well vascularized, so you'd expect a rapid exchange in temperature bewteen the capillaries and the extracellular fluid.

[Lucid1014]

I can't really cite a specific example from when it happend, its actually been awhile now, so I don't really think its anything serious... I remember in basic training it happened alot...like whenever I stood up or got out of bed too quickly, I would see red, or black, and get really lightheaded. But like I said it hasn't happened in awhile, and doesnt happen when I work out now.

[oldman34]

That used to happen to me alot too (getting lightheaded when standing) However I stay fairly well hydrated. Are you eating right?

[jubei33]

yeah, youre right, I made alot of mistakes in that one. After cross checking some more some of it was some bad information. In particular, I was surprised at the different conclusions for the paper...I need some more reading, got any good sources?

[Judah Maccabee]

www.pubmed.com

Put in keywords of interest and go nuts.

[Tef-the-Persian]

I'd like to back up dakotajudo on the issue of where we get the majority of our water: it is from beverages by far, not food.