I have not read any articles stating that they are. Amino acids, which are what protein supplements are derived from, are hard on the liver. Most kidney stones are an accumulative effect of uric acid, which alcohol, and rich food contributes to. The diet should be rich in magnesium, and calcium, green leafy vegetables.And water,to flush the kidneys. Gout and kidney stones are closely related to each other. As both are uric acid, just in different places. Some, stones are calcium, so therefore, calcium supplements might present a problem. If the body is too acidic, it will leach calcium out of bones, resulting in stones. The suggested supplement to rejuvenate the liver is milk thistle. So, it might help if you are concerned. See my article https://hubpages.com/health/Natural-Treatments-for... For more help on treatment, and prevention, of kidney stones.