It is not impossible for food to lead to high calcium levels in the blood, but it is very rare. Therefore, diet is not normally a suspected cause in cases of high blood calcium, or hypercalcemia.
Before the development of modern antacids, people suffering from stomach ulcers sometimes sought relief by drinking large amounts of milk and taking large amounts of calcium-based antacids. Milk intake contributed to elevated blood calcium in these cases. However, advances in ulcer treatment have made this a very rare cause of hypercalcemia.
Hyperparathyroidism is a typical cause for hypercalcemia. The parathyroid glands release a hormone that causes bones to release calcium into the bloodstream, increases absorption of calcium from food and reduces calcium excretion in urine. Other known causes of hypercalcemia include certain cancers, excessive calcium or vitamin D supplementation, and certain medications.