Protein And Uric Acid Connection
July 18, 2007 in Gout
Yesterday, somebody asked me "What is the protein and uric acid connection?"
I can sum it up in two words.
But you want more than that, don't you?
The simplest explanation is that purines from cell metabolism and some foods get broken down to uric acid in the human body. Most other animals produce other enzymes (uricase) that continue to breakdown uric acid further, so that it is easier to excrete. Humans do not have that enzyme because we want to keep some of the uric acid. It neutralizes free oxygen radicals in our body that would otherwise cause extensive cell damage. That is why normal human lifespan is greater than many animals.
From that, we can see that the protein and uric acid connection is a simple one:
but if we get too much it causes gout.
The trouble with simple explanations is they lead to simple gout solutions. "Stop eating high purine foods and your gout will be cured," is one of them.
In real life, eating a low purine diet has been shown to have a minimal effect on uric acid levels and on gout. A study(1) of 60 gout patients showed a 1 mg/dL reduction after 7 days, though they note that no significant reduction occurred after 5 days. What we don't know from this study is just how the diet changed. What replaced the purine foods? Could this account for the reduction?
Even that study was just a preliminary to determine the number of days of diet change required to have a significant effect on uric acid. The main part of the study, and several other similar studies show that changes to the purine content of diet has a much bigger effect on the amount of uric acid excreted in urine than it does on uric acid in the blood.
Not only that, but there are several different types of purines. Nearly all published information about the purine content of food, including my own purines in food table, relates to total purines. Each of these follows a different pathway in our bodies. The presence of different enzymes controls if and how these purines breakdown to uric acid. Some become reabsorbed at different stages. Finally, the kidneys reabsorb or excrete uric acid according to mechanisms in our bodies that are not fully understood.
Several studies have taken place, and no doubt more will continue, to try to understand the protein and uric acid connection. Many of these studies show, that by introducing artificial diets (necessary to achieve scientific control points), then adding different oral purine compounds (2), there is a direct connection between protein and uric acid.
The problem with this, is that it does not help us gout sufferers in the real world. The interaction between food and body chemistry is too complicated for simple "No Purine" rules. What about naturally occurring antioxidants in foods in our diets? Do these have a neutralizing effect that might help prevent the formation of excess uric acid? What about compounds in food that restrict the activity of enzymes that cause the breakdown of purine proteins to uric acid - a kind of natural allopurinol?
Many questions reveal themselves as the protein and uric acid connection gets more complicated. I don't have answers for all of them, but I'll be revealing some significant aids to understanding over the next few weeks.
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(1) URIC ACID PRODUCTION IN GOUT By J. E. SEEGMILLER, ARTHUR I. GRAYZEL, LEONARD LASTER AND LOIS LIDDLE. (From the National Institute of Arthritis and Metabolic Diseases, Bethesda, Md.)
(2) Effect of Oral Purines on Serum and Urinary Uric Acid of Normal, Hyperuricemic and Gouty Humans
A. J. CLIFFORD,1 J. A. RIUMALLO, V. R. YOUNG AND N. S. SCRIMSHAW
Department of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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