Blood pressure responses to high-calcium skim milk and potassium-enriched high-calcium skim milk.
OBJECTIVE
This study was designed to evaluate the effect of high-calcium skim milk or potassium-enriched high-calcium skim milk on blood pressure compared with nonenriched skim milk.


METHODS
This was a randomized double-blind controlled trial. Each milk intervention lasted for 4 weeks, with a minimum of 4 weeks of wash-out between interventions.


METHODS
We recruited 38 healthy people, aged over 40 years, to take part in a double-blind, randomized, controlled cross-over study. We asked them to replace their usual liquid milk with two servings per day of skim milk (control), high-calcium skim milk or potassium-enriched high-calcium skim milk. We measured office blood pressures (seated and standing) at the start and after 2 and 4 weeks of milk intervention and we measured daytime ambulatory blood pressures at the start and after 4 weeks of milk intervention. Each milk intervention was interspaced by a 4-week interval.


RESULTS
Office systolic blood pressure (standing) decreased from 127 +/- 16 to 124 +/- 16 mmHg (P<0.05) after 4 weeks of skim milk and from 130 +/- 18 to 126 +/- 17 mmHg (P<0.05) after 4 weeks of high calcium skim milk. After 4 weeks of consuming the potassium-enriched high-calcium milk, systolic blood pressure decreased from 125 +/- 18 to 117 +/- 16 mmHg (P<0.001) seated, and from 130 +/- 16 to 122 +/- 15 mmHg (P<0.001) standing. There were no significant changes in office diastolic blood pressure after any milk. There was no change in ambulatory blood pressure after either skim milk or high-calcium skim milk. After 4 weeks of potassium-enriched high-calcium milk, ambulatory daytime systolic blood pressure decreased from 138 +/- 13 to 135 +/- 11 mm Hg (P<0.05) and daytime diastolic blood pressure decreased from 80 +/- 8 to 78 +/- 9 mmHg (P<0.05).


CONCLUSIONS
High-calcium milk enriched with potassium has a small hypotensive effect in healthy people aged over 40 years.
Hilary Green
J
J
Milk and Health Research Centre, Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand. J.H.Green@massey.ac.nz
Richards
J K
JK
Bunning
R L
RL
D000328:Adult; D000368:Aged; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D015924:Blood Pressure Monitors / Q000592:standards; D002118:Calcium / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004435:Eating; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008892:Milk / Q000737:chemistry*; D008903:Minerals / Q000652:urine; D011188:Potassium / Q000008:administration & dosage*; D015203:Reproducibility of Results
D008903:Minerals; D011188:Potassium; D002118:Calcium