A study of melatonin involved 18 women, ages 47 to 63, half with hypertension being successfully controlled with ACE inhibitor medication and half who had normal blood pressure. For three weeks, participants took either 3 mg of time-released melatonin (a supplement typically used to promote sleep) or a placebo one hour before bed. They were then switched to the other treatment for another three weeks. After taking melatonin for three weeks, 84% of the women had at least a 10 mm/Hg decrease in nocturnal (nighttime) systolic and diastolic blood pressure, while only 39% experienced a decrease in nocturnal blood pressure after taking the placebo. The reduction was the greatest in those with controlled hypertension. In both groups, no change was found in daytime blood pressure readings. Previous studies have found similar results when men with untreated hypertension took melatonin.

My view: Melatonin, a hormone produced by the pineal gland in the brain, is secreted in response to darkness and promotes a normal sleep cycle. A deficiency of melatonin may prevent relaxation of the cardiovascular and nervous systems, increasing blood pressure. (Normally, heart rate and blood vessel constriction decrease at night.) While people with hypertension often monitor their daytime blood pressure, they usually are unaware of their readings at night. This can be a mistake. High nighttime blood pressure is just as important as high daytime pressure.

For people with high blood pressure whose levels also tend to be elevated at night, I recommend taking I mg of time-released melatonin one hour before bed. To determine if you have elevated blood pressure at night, use a home blood pressure monitor to test levels several times during the day and twice a night (at midnight and 4:00 am) for three days.

Caution: Consult your doctor before trying melatonin. It may require an adjustment to your blood pressure medication. Women who are pregnant or breastfeeding, as well as those taking birth control pills, should not use melatonin.

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