Electrolyte and pH changes in Human Milk

Abstract

Summary: Milk samples from 100 lactating mothers in the 10 days following delivery have been analyzed for pH, sodium, and potassium. The sodium concentration was high in the first 5 days, mean 21 ± 5 mmol/liter, but fell to a mean 15 mmol/liter by the end of the first week and 12 mmol/liter by the 10th day. A similar downward trend was shown for potassium with an initial mean concentration of 18.5 mmol/liter falling to 15 mmol/liter by the 10th day. The pH fluctuated widely from day to day through a range of 6.75–7.42 with a mean pH 7.09. Considerable variations were shown in individuals from day to day, and from the beginning to the end of feeds (Table 1). The relatively high sodium concentration in the firs> few days may be an important defense mechanism against dehydration and hyponatremia during a period of relative thirst and starvation. The variation in the pH and electrolyte content of human milk may be expected to have some influence on the acid-base and electrolyte status of the infant. Speculation: Hyponatremia and acidosis in neonates in the first few weeks may be attributed in part to the inappropriate pH and electrolyte content of artificial milk formulas based on mature human milk. The addition of sodium and base to formulas may be a desirable modification both for premature infants and for term infants in the first few weeks of life.