The man, named Mr He, underwent a two-hour operation to remove the stones at a hospital in Dongyang, eastern Zhejiang Province, the Qianjiang Evening Post reports . Doctors at the hospital say it's likely that his tofu-heavy diet, and a lack of water, are to blame. "Soy products, especially gypsum tofu, are very high in calcium, the excess of which cannot be excreted from the body without a sufficient intake of water," says Dr Wei Yubin.