Gout, Purine-Rich Foods, and Red Herrings

That purine-rich foods can cause the uric acid deposition associated with gout was established years ago. But the relationship between these foods has always been complicated. For instance, purine-rich vegetables don't seem as culpable as purine-rich meats.

In July, a well-publicized study showed for the first time that purine-rich foods can also trigger acute and recurrent gout attacks. But are purines being unfairly accused?

In an editorial in the same edition of the Annals of Rheumatic Diseases ("Purine-rich foods: an innocent bystander of gout attacks?"), rheumatologists Pascal Richette and Thomas Bardin of the Hospital Lariboisiere at the University of Paris contend that purines may be an example of guilt by association rather than causation. Here Dr. Richette, who is a professor of rheumatology, tells ConsultantLive why we ought to interrogate another metabolic component instead.

Your editorial states that the "elegant report ... shows for the first time that high purine intake, in addition to being a well-known long-term risk factor of urate deposition, also increases the risk of gout attacks.” Is this surprising? Isn’t it logical to assume that besides promoting urate deposition, high purine intake would also trigger gout attacks?

It is not logical at all, since the mechanism that leads to urate deposition, i.e the chronic hyperuricemia, is totally different from the one that triggers acute  attacks, which is IL-1 dependent. The former is due to the physical properties of urate that crystallizes when its concentration is above its saturation point (about 400 microM), whereas the latter is a complex phenomenon, which involves the inflammasome and many cytokines.    

Actually, this study is not in itself a surprise for the "goutologists", because we knew from our patients for a long time that some purine foods could trigger acute attacks. But it has had never been demonstrated in such a study.  

The study was based on surveys and, as you point out, lacks details on urate levels. Do you think it needs to be repeated and amplified before practicing doctors can advise their patients that a purine-rich diet, even for a day or two, is likely to cause a gout attack?  

No.  Information on urate levels would have been interesting of course, but is not a key point for the results of this study 

As you point out, because urate crystals take years to develop, high purine intake is “unlikely to trigger flare by acute crystallization of [monosodium urate] in synovial fluid.” You suggest, based largely on the study by Joosten et al in Arthritis & Rheumatism, that free fatty acids (FFA) increased after heavy eating or alcohol consumption may trigger joint inflammation, due to release of interleukin-1-beta. Does FFA-induced inflammation correlate with any other known diseases?

Not to my knowledge. Actually, FFA does not induce "inflammation", but is a sort of "second signal" necessary for generating inflammation caused by crystals.   

In general, do purine-rich foods also have high levels of fatty acids?

Yes, in particular in meats. (Ask McDonald's and Burger King!)

Do you believe it is worth testing the effects of fat-reducing drugs such as statins to prevent gout attacks? 

Yes, this sounds a good idea, although I'm not sure that statins prevent the rise in FFA levels that
occurs after important ingestion of purine-rich foods


 

Source:  Gout: Excess Calories, Purines, and Alcohol Intake and Beyond. Response to a Urate-Lowering DietJ Rheumatol May 2005


Further information:

Purine-rich foods intake and recurrent gout attacksAnnals of Rheumatic Diseases, July 2012

The Association of Dietary Intake of Purine-Rich Vegetables, Sugar-Sweetened Beverages and Dairy with Plasma Urate, in a Cross-Sectional StudyPLoS One, June 2012

Intake of Purine-Rich Foods, Protein, and Dairy Products and Relationship to Serum Levels of Uric Acid: The Third National Health and Nutrition Examination SurveyArthritis & Rheumatism, January 2005