Are calcium supplements safe if I have pseudogout?

Pseudogout is a type of inflammatory arthritis characterized by sudden attacks of pain and swelling in the joints. It closely resembles gout, hence the name. But gout usually affects a big toe, and pseudogout usually affects the knee, though both conditions can affect other joints as well. Gout is caused by sodium urate crystals, and pseudogout is caused by crystals of calcium salts -- calcium pyrophosphate dihydrate, or CPPD.

CPPD crystals initially form in the cartilage and migrate into synovial fluid, stimulating inflammation in the joint. Most people with x-ray evidence of CPPD crystals never have symptoms, but some develop pseudogout, as well as chronic arthritis. We don't know why calcium crystals form in joints, but they may result from elevated levels of calcium or pyrophosphate or other factors that lead to supersaturation of calcium pyrophosphate in cartilage and bone.

Risk factors for pseudogout include family history, trauma to the joint, and older age.

As long as your body is metabolizing calcium normally, dietary calcium or a calcium supplement should not increase CPPD formation. Calcium metabolism is a tightly regulated system. Calcium from food or supplements is absorbed in the gut and transported into the blood for use in most cell functions, including bone formation. If we absorb more than we need, our kidneys excrete the excess. However, certain conditions can undermine these controls, causing high blood calcium levels and predisposing a person to forming CPPD crystals.

Conditions associated with pseudogout include causes of excessive calcium in the blood such as an overactive parathyroid gland (hyperparathyroidism); low blood levels of magnesium; an underactive thyroid gland (hypothyroidism); and excess iron in tissues (hemochromatosis). Your doctor can perform blood tests to check for these conditions. If those are normal, you can safely take the calcium (and vitamin D) you need to reduce your risk for osteoporosis.