With a personal history of kidney stones, I started to get concerned that my morning smoothie might be putting me at risk. Smoothies have a high concentration of oxalates, and about about 80% of kidney stones are made up of calcium oxalate. Oxalates are naturally present in our bodies. They are also present in varying levels in certain plant foods. Low-oxalate diets are sometimes recommended to decrease the kidney stone development. Just eating 5 to 10 grams of gelatin significantly increased oxalates in the urine for six hours. How much collagen is in meat? Samples of lean meats contain from 2.5 to 5% collagen by weight and hamburgers are up to 7.1%. Hot dogs and sausages, made from scraps and pieces, are up to 19% collagen by weight. Meat that contains 7% collagen will have 7 grams per serving and 10 grams per about one third of a pound. Meat servings in the range of a hot dog or quarter pounder will increase urinary oxalates for an entire day after consumption. Several dietary supplements promoted for skin, bone, and joint health also contain gelatin at 10 grams per recommended dose. Although oxalate-rich foods enhanced excretion of urinary oxalate in normal volunteers, the increase was not proportional to the oxalate content of the food. Fruits and veggies that are high in oxalates are often high in calcium too, which prevents the absorption of the oxalate by binding it up in the intestine. Increased dietary calcium intake may reduce urinary oxalate excretion by binding more oxalate in the gut. Collagen in meats break down into hydroxyproline, which then breaks down into oxalates. Meat represents a significant source for oxalates in omnivores. One serving of meat increases urinary oxalate levels for 24 hours. Decreasing meats and processed dairy cuts the risk of kidney stone by 40%. Check out your supplements and reconsider gelatin-containing products. Avoid gelatin-containing foods and desserts.
