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Increased sodium concentrations in drinking water increase blood pressure in neonates
Avishalom Pomeranz1, Tzipora Dolfin, Ze'ev Korzets
1Unit of Pediatric Nephrology, Meir General Hospital, Sapir Medical Center, Kfar-Saba and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. avip2@clalit.org.il
Insights
High-sodium water significantly increased infant blood pressure and salt intake compared to low-sodium water. Using low-sodium water for formula is recommended to match breast milk sodium levels and support healthy infant blood pressure.
Area of Science:
- Pediatrics
- Neonatal Health
- Cardiovascular Physiology
Background:
- Previous research linked increased sodium intake to elevated blood pressure in children.
- Milk formula typically has low sodium, similar to breast milk.
- Sodium concentration in prepared formula varies with the water used for dilution.
Purpose of the Study:
- To assess blood pressure changes in neonates fed formula diluted with low-sodium mineral water (LSMW) versus high-sodium tap water (HSTW).
- To compare these changes against a breast milk-fed control group over the first 8 weeks of life.
Main Methods:
- A randomized prospective study involving 58 term infants fed formula.
- Infants received formula diluted with either LSMW (32 mg/l sodium) or HSTW (196 mg/l sodium).
- Blood pressure, weight, height, and head circumference were monitored weekly for 8 weeks; urinary sodium/creatinine ratios were measured monthly.
Main Results:
- No significant differences in weight, height, or heart rate were observed between groups.
- Infants receiving HSTW showed significantly higher mean arterial pressure (MAP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) from 6 to 8 weeks.
- Higher urinary sodium:creatinine ratios were noted in the HSTW group, indicating increased salt intake.
Conclusions:
- Diluting infant formula with high-sodium tap water results in a high-salt diet for neonates.
- Low-sodium water should be used for formula preparation to achieve sodium levels comparable to breast milk.
- Elevated sodium intake through drinking water can increase neonatal blood pressure.
Background:
In a previous study, we found that increased sodium concentrations in the drinking water led to an increase in mean arterial pressure (MAP) and systolic blood pressure (SBP) in fourth- and fifth-grade school children. Milk powder formulae have a low content of sodium, almost identical to that of breast milk. However, the final sodium concentration in the milk formula depends upon the concentration of sodium in the diluting water, which varies remarkably.
Objective:
To evaluate changes in blood pressure during the first 2 months of life in neonates receiving low-sodium mineral water (LSMW), high-sodium tap water (HSTW), or breast milk.
Design:
A randomized, prospective study in a teaching hospital.
Methods:
Fifty-eight Jewish term infants maintained on milk formula were randomly assigned to two groups. Group 1 consisted of 25 infants whose formula was diluted with LSMW (Eden Spring Mineral Water) having a sodium concentration of 32 mg/l (1.4 mmol/l). Group 2 contained 33 infants whose formula was diluted with HSTW having a sodium concentration of 196 mg/l (8.5 mmol/l). Fifteen breastfed babies served as the control group (group 3). Weekly weight, height, head circumference, heart rate, and systolic (SBP), diastolic (DBP) and mean (MAP) blood pressures were recorded for each infant for 8 consecutive weeks after birth. After 8 weeks, group 1 reverted to a diet similar to that of group 2. At 6 months of age (week 24), a follow-up blood pressure measurement was performed in 11, 20 and seven infants in groups 1, 2 and 3, respectively. Blood pressure was measured during sleep. Urinary sodium : creatinine ratio was determined monthly during the initial 2 months.
Results:
Increases in weight and height were equal in all groups. Heart rate did not differ between groups during the entire study period. From the age of 6 weeks until week 8, MAP, SBP and DBP were found to be significantly greater in the group 2 (HSTW). In parallel, the urinary sodium : creatinine ratio was significantly greater in this group. At week 24, blood pressure values in group 1 increased towards those of group 2.
Conclusions:
Diluting milk formula with tap water containing a high concentration of sodium will result in the infant being fed a high-salt diet. To equilibrate with breast milk, formula should be diluted with low-salt water. Blood pressure in the neonate is increased by a high sodium intake via drinking water.