Here's the short version:
Diets high in purines (animal proteins) can cause a condition call hyperuricemia (fancy word for high blood uric acid levels). The crystals that precipitate out into joints and viscera are called monosodium urate crystals. Articular gout pertains to joints, viseral gout obviously pertains to the viscera. When blood serum uric acid concentration are too high, it increases the chance for both types of gout. Some uric acid gets excreted through urination, however if the kidneys can't excrete it effecient enough or if the kidneys can't handle the volume of urates, it raises blood uric acid levels.
The primary way (I believe there were some secondary mechanism's of action...I just don't remember and don't feel like looking it up) alfalfa works is it changes the bloods pH (potential for hydrogen) value, and is measured on a scale ranging between 1-14. 1 is acidic 14 is alkaline.....
So it raises the blood pH making it more alkaline (or base...its a higher number...remember 1 is acidic, 14 is alkaline). Alkalinity helps keep the uric acid in solution (blood serum). Obviously if it doesn't precipitate out and stays in solution, it makes it easier for the kidneys to excrete.
I don't have a scale to tell you where the blood uric acid levels would be with use of alfalfa..it depends on how much alfalfa and purines eaten (I'm just making an educated guess on that...but its a reasonable assumption). But since alfalfa causes the blood pH to be more alkaline and urates stay in solution, it helps flush the blood/joint/organs of uric acid crystals via the kidneys. Thus it works as a treatment and preventative measure.
It has a lot of benefits (many, many, many more than just gout)...it also helps prevent kidney uric acid stones (they can cause kidney failure) and bladder stones if they are uric acid stones. Since it helps flush the blood of uric acid, the kidneys don't store it as monosodium urate stones as easy.
If you know your dragon has gout or kidney failure, minimal amount of insect protiens (purines) should be fed. Basically the kidney care diet and gout diet are very similar. So if you want to study it in deeper detail I would suggest looking in a human health care book. Mosby's manual is very detailed and covers a vast amount of info that can be pertinent towards reptile care. Its fairly easy to understand if you have a chemistry or health care background.
Kidney and bladder stones can also be comprised of calcium from high blood serum calcium levels (hypercalciemia), but its more likely to be uric acid stones in reptiles.
I'm unsure if alfalfa helps with calcium stones, (I'm to lazy to look that up right now...but its doubtful) its not pertinent to this discussion anyway.
The best part about alfalfa is its a high protein plant (which doesn't raise uric acid levels..no purines) and it helps prevent gout from a high purine diet.
Now time for my opinion based on valid facts. Adult dragons don't need much insect protein and it can cause more health issues (in larger amounts) than they are worth. But alfalfa is high in protien...so I feel it is a good choice to make. Besides live feeders are expensive. So why cause potential health problems and spend a lot of money on large volumes of bugs?
Some insect protein is fine...but too much isn't. Young dragons need a higher protein diet due to growth and development...but should be gradually weaned off so many insects as they grow.
There are always posts on here about adult dragons with gout...its totally preventable unless the dragon has a metabolic issue. People have spent a bunch of money on vet visits and allopurinal to clear a gout and kidney issues related to high protein diets. Worst of all the diet isn't totally healthy for the dragon.
I don't expect anyone to take what I say as gospel, nor do I want anyone to. I encourage everyone to do their own research on anything they are interested in and formulate their own opinions. But my info is usually well thought out....
Mellisa Kaplin and I had a similar protein discussion about 25 years ago. It was related to iguanas....but she added much of the protein related issues we discussed on her care sheets. She's very knowledgeable and has done a bunch of research on iguanas, water dragons, and bearded dragons. Her info is usually easy to find by doing a name search. I highly recommend doing that. I wasn't aware of the use of alfalfa back then or I would have mentioned it. I have found stuff I posted from 25 years ago still floating around the net...some I wish would disappear
Katherine Tosney also has a bunch of my info on her
bearded dragon care pages also. I think most of it had to do with false gravidity and egg binding though. Again, that was about 25 years ago, so long ago I almost forgot about it. Highly recommended for awesome dragon info.
Sorry this is a lot of typing and I'm trying to remember all my chemistry and nursing garbage. This is just the basic version
This will give you a good start. You'll find the rest if interested I'm sure.....
If through your research you find that any of the info provided is inaccurate please let me know.
Forgot to mention something, so fit this into the post somewhere
A purine molocule is rather large and renal tubuals are small. So the molocule can plug up the renal tubuals and cause renal failure. This is especially true if the animal is dehydrated. Animals with gout should also stay very well
hydrated to help flush the uric acid.
Happy studying
(Edited a million times to fix typos and correct my disjointed thought process)