Comparison of serum calcium levels between junior high school children with high-normal and low-normal blood pressure. The child and adolescent blood pressure program.

The objective of this study was to compare serum calcium levels, dietary calcium intake, and urinary calcium excretion between junior high students with high-normal and low-normal blood pressure. The study was conducted in 11- to 14-year-old children recruited after blood pressure screening of 5th to 8th grade Minneapolis and St. Paul Public School students. Comparisons were made between a group of 243 children selected from the upper 15 percentiles of the blood pressure distribution (high-normal group) and 40 children randomly selected from the lowest 10% of the blood pressure distribution (low-normal group). Blood samples were obtained from the participants at clinic visits conducted after school. Calcium measurements were based on the principle that serum calcium is found in three forms: 1) an ionized fraction; 2) a fraction complexed with organic anions such as citrate, phosphate, and lactate; and 3) a protein-bound fraction. Dietary calcium intake was determined from food diaries, and urinary electrolytes were determined in 24-h urine collections. Serum total calcium levels were not significantly different between groups. However, serum ultrafilterable, true ionized, ionized normalized for pH, and complexed calcium levels were significantly greater in the low-normal group. There was no significant difference in 24-h intake of calcium or other nutrients between the groups. The low-normal group excreted significantly more calcium than the high-normal group, but there were no significant differences in sodium, potassium, or chloride excretion. This report of the relation between calcium and blood pressure represents the first study in children or adolescents to include serum, dietary, and urine data.(ABSTRACT TRUNCATED AT 250 WORDS)