People should avoid taking the antacid calcium carbonate in doses larger than half a gram, for despite its capacity to neutralize stomach acids, calcium carbonate can increase the calcium level in the blood and thus impair kidney function. Moreover, just half a gram of it can stimulate the production of gastrin, a stomach hormone that triggers acid secretion. Which one of the following is most strongly supported by the information above? ['Half a gram of calcium carbonate can causally contribute to both the secretion and the neutralization of stomach acids.', 'Impaired kidney function may increase the level of calcium in the blood.', 'People who avoid taking more than half a gram of calcium carbonate are less likely than average to suffer from impaired kidney function.', 'Doses of calcium carbonate smaller than half a gram can reduce stomach acid more effectively than much larger doses do.']