Oxalates are natural compounds in some plant foods that can bind to calcium in the body. Excess oxalates may form calcium oxalate kidney stones—8 in 10 stones are this type. High-oxalate foods include spinach, beets, rhubarb, and black tea. To reduce risk, stay hydrated, limit salt and protein, avoid high-dose vitamin C, and eat calcium-rich foods like broccoli and kale with meals. Proper cooking can reduce oxalate content in plant foods.

According to population studies on magnesium intake, there’s a good chance that you might have magnesium deficiency. Less than 30% of...