Which factor can lead to metabolic acidosis?

Metabolic acidosis occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body, leading to a decrease in blood pH. Prolonged diarrhea can lead to metabolic acidosis because it results in the loss of bicarbonate, a base that helps to neutralize acids in the body. The intestines secrete bicarbonate to maintain a balanced pH, and when diarrhea is present, this bicarbonate is lost along with the stool. The loss of bicarbonate contributes to an overall increase in acidity in the blood, resulting in metabolic acidosis.

In contrast, the other options do not directly lead to metabolic acidosis. Excessive sodium intake typically relates to fluid retention or hypertension rather than acid-base balance. Inadequate fluid intake can cause other types of imbalances but does not specifically lead to metabolic acidosis. High calcium levels, a condition known as hypercalcemia, is not associated with the production or retention of acid in the body, thus not contributing to metabolic acidosis.