What's the Function of Water Retention?

Factual Questions
1

Are there any benefits to it? If I eat too much, I’ll store some food energy in fat, which could help in times of famine (Not that I’ve been through any of those.) But from my very limited understanding, water retention (edema) doesn’t work that way. Water filters from the blood to the tissues, where it can sit for days or weeks.

My question is, does the body retain fluids for a possible beneficial reason? I can’t find any sources that say if you retain water and then don’t drink water, the excess stores in your tissues will take care of the problem. In fact, for edema caused by hormones, the advice is to drink lots of water to “flush out” your system. I am unclear why this would work, unless the edema is caused by excessive amounts of sodium.

Also, aside from obvious health problems like congestive heart failure and aside from consuming too much sodium, why do we retain fluids? If I’m going to squish when I walk, I’d like to know there’s a sensible reason for it.

Thanks!

2

Well if you don’t retain any water, then you dehydrate, become hypovolemic, the concentration of electrolytes in your blood skyrockets, and you die. The benefits of retaining water are pretty obvious in this regard.

3

Yep, it’s a survival mechanism. Camels get really bad water retention too. So bad they get a hump or two on their back.

4

Often it is.

5

My understanding is that the humps are composed largely of fat. The water storage idea is a myth.

I am not asking about water to maintain normal blood volume. When people retain water, they tend to retain it in their tissue. Of course, sometimes people consume too much salt and retain water, but that doesn’t explain why, say, premenstrual women do, even when they curb their sodium intake. And if it’s the body’s way of ensuring there’s enough fluid in the system, then what (besides salt) triggers it? How does it “recognize” that there may be more water needed in the near future?