Melatonin May Lower High Blood Pressure

AMSTERDAM, The Netherlands--Repeated nighttime melatonin supplementation may lower high blood pressure (BP), according to a study in the upcoming February issue of Hypertension (43, 2, 2004) (hyper.ahajournals.org). Melatonin plays a role in regulating a persons internal clock (also known as circadian rhythm), which appears to be disturbed in people with high BP.

The randomized, double blind, placebo-controlled, crossover trial involved 16 men with untreated hypertension. Subjects were given either 2.5 mg/d of melatonin 1 hour before bedtime for three weeks, or 2.5 mg of melatonin only once, followed by an inactive placebo for the remaining course of the three-week period. Researchers found repeated melatonin intake reduced systolic BP during sleep by 6 mm Hg and diastolic BP by 4 mm Hg, and also improved sleep. Heart rate was not affected, and improvements in BP were not related to sleep. Conversely, the single dose of melatonin had no effect on blood pressure, nor did it improve sleep.