I think I'm getting a better handle on this puzzle. I think the medical community views frequently very bubbly urine as abnormal because the average they are comparing to is the SAD, which contains less meat/fish protein than our diets tend to contain. I didn't think it was a major problem in my case and attributed it to my diet that is relatively high in meat/fish protein, plus heavy water intake in combination with mild dehydration, but I couldn't find sources to support this until now (see below).
The most concerning thing in my case is that even with high intake of water I continue to have mild dehydration, although it is reduced, so I'm not hugely concerned. I'm also prone to constipation and dry skin, which also suggest dehydration as one possible element. I'm thinking that I may have a combination of deficient signals to consume liquids plus deficient ability to absorb water. I'm not sure what could be causing this. I sweat less than most people, so excess sweating is not an issue. Apparently water goes through me and into my urine to an excessive extent, instead of being properly absorbed.
Thin skin and diabetes have also been suggested (
http://www.righthealth.com/topic/Dehydration/Causes). I do have thin skin. I don't have diabetes, but I do have a history of symptoms that have been connected to insulin resistance and hypoglycemia.
The three most common factors in foamy urine appear to be...
1. mucoproteins from diets high in meat/fish protein or gluten protein in people with gluten intolerance (in the former case it's apparently normal, in the latter case it's a problem because the partially undigested gluten proteins can trigger the immune system and cause other problems)
2. concentration of the urine that occurs with the first urination of the day or dehydration
3. forcefulness of the urine flow, which mixes more air with whatever protein is present to create bubbles (however, I've had forceful flow of high-volume urine without much in the way of bubbles, so this factor is not sufficient by itself)
So the first urine of the day after a heavy protein meal the night before will tend to produce rather foamy urine, which I find to be the case for me.
Gallbladder and kidney issues are rarer but should be checked for if the urine is constantly foamy throughout the day.
Mucoproteins in the urine
http://www.diagnose-me.com/questionnaire/Q158.htmlThis article says "If the urine is extremely foamy and continues all the time, there may be a problem with bile salts or the gallbladder." In my case the foam is not always present, so I doubt this applies to me. My guess is that mucoproteins and forcefulness of flow are more common causes.
Concentration of the Urine and Dehydration
http://forum.bodybuilding.com/showthread.php?t=6530271"When people eat large amounts of meat and fish, the large quantity of mucoproteins ingested because of this are not fully broken down by the body, and pass into the urine through the kidneys. This is not a sign of kidney damage neccessarily, everyone has foamy urine now and then.
It will be more pronounced when you are dehydrated or when your urine is more concentrated, such as first thing in the morning. It occurs because the proteins react with the air as they pass into the toilet, and then form bubbles in the water.
Persistent foamy urine should be a sign to cut back on your protein intake. Things to also get checked for are gall bladder problems, glomulonephritis and nephrotic syndrome, though the last two are generally present with blood in the urine also.
Get your urine checked by a doctor anyway, to check for white blood cells, glucose and abnormal levels of proteins as well as for the presence of red blood cells."
Forcefulness of the urine flow
http://www.buzzle.com/articles/bubbles-in-urine.html
