Although a vegan diet is much healthier than the standard American diet (S.A.D.), there is one potential pitfall of this diet in that many of the healthiest plant-based foods contain high levels of oxalate. Oxalate is a chemical that can be toxic when consumed in high doses. In the majority of people, it's usually not a problem - the oxalate combines with calcium in the intestines and passes through the body mostly without being absorbed, and any oxalate that is absorbed generally passes through the urine without incident.
In a small percentage of individuals however, oxalate can bind with other substances in the body, like calcium. This can form kidney stones which are so excruciatingly painful that medical intervention is required. Calcium oxalate stones are the most common form of kidney stones and recent studies show a correlation between low dietary calcium and kidney stones.
Essentially, much of the calcium in plant-based foods breaks down quickly and is easily absorbed by the body. This is wonderful for bones and teeth, but it means that there is less available calcium in the digestive tract to bind with the oxalate and prevent it from being absorbed. Calcium in dairy does not break down so easily and therefore will bind with oxalate. Most of the calcium in dairy passes out of the body without being absorbed, which is why studies have shown a high correlation between increased dairy consumption and osteoporosis.
Although most vegan health experts will say that over-the-counter calcium is useless because the body doesn't absorb it, the irony is that for vegans who suffer from kidney stones, this kind of calcium is exactly what they need. Taking a calcium carbonate supplement with meals gives the oxalate something to which it can bind, allowing it to pass harmlessly out of the system. Combining this approach with cutting down on the highest oxalate foods, should insure that kidney stones in vegans can be avoided. Additionally eating plant-based calcium-rich foods will insure that your teeth, bones and organs get the calcium they need.
Although the list of foods containing oxalate is extremely long, some of the worst offenders include chocolate, rhubarb, spinach, Swiss chard, beets and almonds.
