Uric acid is a waste product that forms from the degradation of genetic material such as DNA and RNA. Uric acid is benign at normal levels. However, if excessive levels of uric acid build up and form needle-like crystals in the joints, it can cause a painful inflammatory arthritic condition known as gout. This is most likely to occur in the joint at the base of the big toe. Soy milk is more capable of causing high uric acid levels compared with cow's milk.
The human body creates uric acid from the breakdown of purines, which form the building blocks of genetic material. Eating foods that are high in purines will generally cause uric acid levels to rise in the blood. Cow's milk and soy milk, despite the similarity in their names, come from two very different organic sources, so their purine contents are also quite different. Cow's milk is low in purines, whereas soybeans contain a moderate amount of purines.
Uric Acid Levels
A 1991 study in "The American Journal of Clinical Nutrition" found that uric acid levels in the blood decreased three hours after the ingestion of milk proteins, but increased after the ingestion of soy proteins. This result does not mean that you should stop drinking soy milk, since purines are an essential nutrient. However, you may need to limit soy milk if you are in danger of excessive uric acid levels. According to the Florida Agency for Health Care Administration, consuming large amounts of soy can make gout worse. If you are not at risk, then soy may have only a minimal impact.
Researchers have known for years that dairy increases the excretion of uric acid, though the mechanism still isn't entirely well understood. A study in a 2004 issue of "The New England Journal of Medicine" found that men who ate dairy products actually decreased their risk for gout. Low-fat dairy appeared to have the greatest effect. The researchers did not study soy products.
If you have already developed gout or are at risk for it, then your doctor will likely recommend a low-purine diet. This diet entails limiting foods high in purines, such as meat and seafood. Fortunately, low-fat cow's milk is a source of protein and a way to reduce your risk of gout. If you do choose soy milk, then you should drink it in moderation. Diet is only one part of a treatment for limiting uric acid levels. It may not be sufficient in all cases.
- The New England Journal of Medicine: Purine-Rich Foods, Dairy and Protein Intake, and the Risk of Gout in Men
- Florida Agency for Health Care Administration: Soy
- The American Journal of Clinical Nutrition: Milk- and Soy-Protein Ingestion: Acute Effect on Serum Uric Acid Concentration
- MedlinePlus: Gout