Melatonin is a hormone that helps regulate sleep and wake cycles. It is produced in the pineal gland. Synthesis and release of melatonin are stimulated by darkness and inhibited by light, displaying a circadian rhythm.
Melatonin secretion increases in late evening and then gradually falls during the second half of the night. Daytime blood serum levels are around 10 picograms/mL; for younger adults the late evening peak is in the range of 60-180 pg/mL but after age 40 it decreases to 10-60 pg/mL.1
Biosynthesis of melatonin begins with the amino acid tryptophan. This amino acid is converted by tryptophan hydroxylase to 5-hydroxytryptophan, decarboxylated to serotonin, and then converted to melatonin via a two-step process.
Melatonin can be found in plants and animals, but diet is not considered a significant source of melatonin.
Melatonin is metabolized in the liver by hydroxylation and conjugation with sulfuric acid followed by excretion in the urine.2 High oral doses can exceed the ability of the liver to process melatonin, resulting in prolonged elevated serum concentrations.3
Oral doses of melatonin in the range of 0.3 to 1.0 mg result in serum concentration range as from endogenous synthesis.3
Oral doses of 10 mg melatonin produce a serum concentration peak of 10,000 pg/mL - one hundred times higher than the normal physiological peak.3
For insomnia and sleep disturbances doses in the range of 1-3 mg melatonin appear sufficient.
Jet lag may need up to 5 mg melatonin, but only for a few days. In 2011 the European Food Safety Authority (EFSA) approved a health claim for 1.0 mg melatonin for sleep assistance and 0.5 to 5.0 mg melatonin for jet lag.4,5
Melatonin should not be taken for longer than two weeks. Higher doses or prolonged periods should only be attempted under medical supervision.
Melatonin is available in capsules, liquid, lozenges, sublingual tablets, teas, and timed release tablets.
No apparent overdose consequences have been seen in people taking up to 10 mg/day for one month, although high doses are not recommended.
Prolonged use, especially at higher doses, may interfere with sleep patterns.
Several human trials have demonstrated that 1 to 3 mg melatonin per day in adult subjects may lead to lower blood pressure,6-9 lower glucose tolerance,10 lower insulin sensitivity,10 and may also change reproductive hormone levels.11,12
Women who are pregnant or breastfeeding should not take melatonin because this supplement may have significant hormonal effects.
People with asthma should consult with their physicians before using melatonin. One study showed improved sleep with no effect on asthma symptoms.13 One study found that elevated endogenous melatonin levels were associated with nocturnal worsening of asthma14 and two others found lower endogenous melatonin levels in people with asthma.15,16 Researchers have suggested that melatonin might have immune stimulatory effects that could exacerbate night asthma although further studies are needed.
Melatonin was originally thought to only be produced by animals. Most recently, melatonin has been identified from a wide variety of plant species. There is still dispute about whether there are any clinically relevant dietary sources of melatonin.
Very few fruits have been evaluated for melatonin content. Tart cherries were found to contain 13.5 ng melatonin/g.17 A tart cherry concentrate (60 mL/day, equivalent to 180-200 fresh cherries or 16 oz fresh cherry juice) contained an estimated 85 ěg melatonin and raised urinary melatonin excretion.18 Bananas were found to contain 236 pg melatonin per mg protein.19 Melatonin was detected in grape extract in the range 120-160 ng/g and an isomer of melatonin was found in musts and finished wines.20
Edible seeds also contain melatonin: poppy 6 ng/g, anise 7 ng/g, coriander 7 ng/g, celery 7 ng/g, flax 12 ng/g, green cardamom 15 ng/g, alfalfa 16 ng/g, fennel 28 ng/g, sunflower seeds 29 ng/g, almond 39 ng/g, fenugreek 43 ng/g, wolfberry 103 ng/g, black mustard 129 ng/g, and white mustard 189 ng/g.21 Additional studies are needed to assess the quantity of melatonin in plant foods and to evaluate the absorption of melatonin from foods.
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin) and aspirin can decrease melatonin secretion in the body.
Sedative medications such as clonazepam, diazepam, lorazepam, phenobarbital, zolpidem, and others should not be used with melatonin. The combination of a sedative and melatonin may cause too much sleepiness and could be dangerous.
Birth control pills may increase the amount of melatonin proiduced by the pineal gland. Adding melatonin supplements may cause serum levels of melatonin that are too high.
Beta-blockers such as propranolol (Inderal) inhibit the nocturnal rise in melatonin concentrations.
Melatonin may increase blood sugar and should not be taken with antidiabetes medications except under the supervision of a healthcare professional.
Melatonin may increase the activity of the immune system and should not be taken with immunosuppressant medications.
Antidepressants including tricyclics (amitriptyline), monoamine oxidase inhibitors (MAOIs; isocarboxazid), and others increase concentrations of melatonin in the brain. Antidepressants and melatonin should not be combined except under the supervision of a medical professional.
Since melatonin may slow blood clotting, this supplement should not be taken with medications that slow blood clotting such as clopidogrel, diclofenac, ibuprofen, naproxen, dalteparin, enoxaparin, heparin, warfarin, or others.
Nifedipine GITS is a drug to lower blood pressure. Melatonin may interfere with the activity of nifedipine and the two should not be combined.
Diuretics such as furosemide and calcium-channel blockers such as amlodipine can interfere with melatonin production.
Hydroxyprogesterone decreases plasma concentrations of melatonin by increasing the rate of metabolism in the liver.
Vemurafenib is a drug used to treat melanoma. This drug increases the plasma concentrations of certain compounds metabolized in the liver, including melatonin. If melatonin and vemurafenib must be combined, the dosage of melatonin may need to be adjusted and should only be attempted under the supervision of a medical professional.
Vitamin B12 concentrations influence melatonin secretion in the body.
Caffeine promotes wakefulness, so caffeine should not be consumed in the afternoon or evening if there is intent to use melatonin as a sleep aid.22
The influence of alcohol on melatonin production or metabolism is not clearly understood. Some but not all human trials reported that consuming alcohol reduced blood concentration of melatonin. There is no evidence how alcohol would affect the metabolism of melatonin taken as a supplement.22
Information on the relationship between substances and disease is provided for general information, in order to convey a balanced review of the scientific literature. In many cases the relationship between a substance and a disease is tentative and additional research is needed to confirm such a relationship.
Efficacy of prolonged release melatonin in insomnia patients aged 55-80 years: quality of sleep and next-day alertness outcomes.
A randomized, double-blind, placebo-controlled clinical trial investigated the efficacy of melatonin for improvement of insomnia. A total of 334 people with insomnia participated in the trial (aged 55 to 80 years). After a two-week single-blind placebo run-in period, participants were randomly assigned to receive either 2 mg melatonin or a placebo daily two hours prior to bedtime. The active trial lasted for three weeks. Melatonin supplements were found to significantly improve quality of sleep and morning alertness compared to placebo (26% vs. 15%, p=0.014). Melatonin was also found to shorten sleep latency to a clinically relevant degree compared to placebo (-24.3 vs. -12.9 minutes, p=0.028). Quality of life was significantly improved for the participants in the melatonin group (p=0.034). These results indicate that 2 mg melatonin successfully improved insomnia in this group of participants.23
The effect of melatonin, magnesium, and zinc on primary insomnia in long-term care facility residents in Italy: a double-blind, placebo controlled clinical trial.
A double-blind, placebo-controlled clinical trial investigated a food supplement containing 5 mg melatonin, 225 mg magnesium, and 11.25 mg zinc in 100 g pear pulp for insomnia in long-term care facility residents. Participants consumed the supplement or a placebo (100 g pear pulp) daily for eight weeks one hour before bedtime. Forty-three people participated in the trial (aged 78.3±3.9 years). Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI); additionally, the Leeds Sleep Evaluation Questionnaire (LSEQ), the Short Insomnia Questionnaire (SIQ), and a quality of life survey were completed. Sleep time was determined with a sensor. The supplement resulted in better overall PSQI scores (difference between groups in change from baseline PSQI score=6.8; 95% confidence interval=5.4-8.3, P<0.001), LSEQ improvements (ease of getting to sleep, P<0.001; quality of sleep, P<0.001; hangover on awakening from sleep, P=0.005; alertness and behavioral integrity the following morning, P=0.001), SIQ score (P<0.001), total sleep time (P<0.001), and quality of life (P=0.006) compared to placebo. The results of this trial suggest that a nightly supplement of melatonin, magnesium, and zinc improves quality of sleep and quality of life for people with insomnia in a long-term care facility.24
Effect of melatonin administration on sleep, behavioral disorders and hypnotic drug discontinuation in the elderly: a randomized, double-blind, placebo-controlled study.
A prospective, randomized, double-blind, placebo-controlled trial investigated the impact of melatonin on sleep, behavioral disorders, and hypnotic drug use in a group of older participants. Twenty-two community-living older adults participated in the crossover design trial. Each participant received 5 mg melatonin daily for two months and received a placebo daily for two months. Sleep quality scores were significantly improved with melatonin supplements (1.78+/-0.40) when compared to baseline (3.72+/-0.45, p=0.001) and placebo (3.44+/-0.56, p=0.025). Melatonin supplements also improved depression and anxiety scores (p=0.043 and p=0.009, respectively). One participant discontinued hypnotic drug use during both melatonin and placebo; nine participants were able to discontinue hypnotic drugs during melatonin use; four participants were not able to discontinue hypnotic drugs. This prospective study indicates that melatonin may be useful for improving sleep and behavioral disorders in older people.25
Prolonged-release melatonin improves sleep quality and morning alertness in insomnia patients aged 55 years and older and has no withdrawal effects.
A three week randomized, placebo-controlled trial investigated the effect of prolonged-release melatonin on sleep quality and alertness for primary insomnia patients. One-hundred-seventy participants were randomly assigned to receive 2 mg prolonged-release melatonin or a placebo daily. Participants were diagnosed with primary insomnia and were aged 55 years or older. Quality of sleep was significantly improved by melatonin compared to placebo (-22.5 vs. -16.5 mm, P=0.047). Changes in sleep quality were improved in the melatonin group (0.89 vs. 0.46 units, P=0.003). Morning alertness was significantly improved by melatonin, relative to placebo (-15.7 vs. -6.8 mm, P=0.002). Improvements in quality of sleep and morning alertness were correlated (Rval=0.77, P<0.001). Rebound insomnia and withdrawal effects were not noted. This study suggests that melatonin may be useful for those with insomnia.26
Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work.
A randomized, placebo controlled, crossover design trial investigated the efficacy of melatonin or bright light for assistance for adaptation to swing shift work. Seventeen people working two week rotating schedules with 12 hour shifts, one week at night followed by one week during the daytime, participated in the study. Participants consumed 3 mg melatonin 1 hour prior to bedtime, a placebo before bedtime, or scheduled 30 minutes of bright light during the first 4 hours of work daily. Subjects consuming melatonin subjectively reported less sleepiness than those consuming placebo. Melatonin consumption was also found to increase sleep by slept 15 to 20 minutes per day compared to placebo. Results from bright light exposure were intermediate between the melatonin supplement and the placebo. Overall, the melatonin supplements were found to assist with adaptation to night shift work.27
Potential of melatonin replacement therapy in older patients with sleep disorders.
In a study conducted with elderly melatonin-deficient insomniacs, patients were given 1 to 2 mg melatonin or placebo for 7-day periods. In the preliminary study, 1 week of treatment with 2 mg fast-release melatonin was as effective as the two-month treatment with 1 mg sustained release melatonin. Researchers concluded that melatonin deficiency seemed to be linked to sleep disorders in the elderly. Melatonin replacement may be beneficial in the initiation and maintenance of sleep in the elderly. 28
Sleep-inducing effects of low doses of melatonin ingested in the evening.
Six healthy male volunteers participated in a study that included a total of 9 test sessions with at least 5 days between sessions. Subjects were given oral doses of 0.3 or 1.0 mg melatonin at 3 time points. Researchers found that sleep onset provoked by a single dose of melatonin, resulted not from its effect on biological timing mechanisms, but from a direct action of elevated circulating melatonin concentrations. 29
Phase-dependent treatment of delayed sleep phase syndrome with melatonin.
A randomized, placebo-controlled, double-blind trial investigated the efficacy of melatonin supplements for modification of delayed sleep phase syndrome (DSPS). Thirteen people with DSPS participated in the four week trial. Participants were randomly assigned to receive 0.3 mg melatonin, 3 mg melatonin, or a placebo 1.5 to 6.5 hours prior to dim light melatonin onset. Both 0.3 mg and 3 mg melatonin advanced circadian phase of endogenous melatonin. The time of melatonin administration was strongly correlated with the magnitude of phase advance in dim-light melatonin onset (r2=0.94, P<0.0001); earlier administration was more effective. The results of this small study indicate that melatonin was effective for adjusting circadian clock in people with DSPS and that the timing of melatonin supplements was important for optimizing the efficacy.30
Melatonin and zopiclone as facilitators of early circadian sleep in operational air transport crews.
A repeated-measures, placebo-controlled trial investigated the efficacy of melatonin or zopiclone for improvement of early circadian sleep for people making transatlantic air transport operations. Thirty people participated in the trial. Each participant consumed each of the three medications (placebo, sustained-release melatonin (2 mg), or zopiclone (5 mg)) during one of three transatlantic missions. Participants taking melatonin and zopiclone compared to placebo fell asleep more quickly (p<0.01, p<0.003, respectively), slept more (p<0.02, p<0.005, respectively), had fewer awakenings after sleep onset (p<0.004, p<0.01, respectively), and spent less time awake after sleep onset (p<0.01, p<0.05, respectively). Results from the questionnaires were similar and participants reported improvements in getting to sleep, fewer awakenings, less difficulty returning to sleep, and better sleep quality. Melatonin and zopiclone were not significantly different from each other. The results of this trial suggest that melatonin may help to regulate sleep for people traveling.31
Efficacy of prolonged release melatonin in insomnia patients aged 55-80 years: quality of sleep and next-day alertness outcomes.
A randomized, double-blind, placebo-controlled trial investigated the efficacy of a prolonged-release melatonin supplement (2 mg) for primary insomnia in men and women aged 55 to 80 years. Three-hundred-thirty-four people completed the five week trial. A two-week, single-blind placebo run-in period preceded the treatment phase. Then participants were randomly assigned to receive either a placebo or 2 mg melatonin (prolonged release, double-blind) daily two hours before bedtime for three weeks. Melatonin significantly improved quality of sleep and morning alertness (responder analysis; 26% vs. 15%, p=0.014). Sleep latency was significantly shortened (-24.3 vs. -12.9 minutes, p=0.028). Quality of life was significantly improved by melatonin supplements (p=0.034). This study suggests that prolonged-release melatonin significantly improved measures of insomnia for people with essential insomnia.32
Prolonged-release melatonin improves sleep quality and morning alertness in insomnia patients aged 55 years and older and has no withdrawal effects.
A randomized, multi-center, double-blind, placebo controlled trial investigated the efficacy of melatonin supplements for improvement of sleep quality and morning alertness for people with insomnia. The trial consisted of three phases: first, a two-week, single-blind, run-in period during which all participants consumed a placebo; second, a three-week, double-blind, randomized treatment period during which participants consumed 2 mg melatonin (prolonged-release) or a placebo daily between 1 and 2 hours prior to bedtime; and third, a two-week, single-blind, run out period during which all participants consumed a placebo daily. One-hundred-seventy people with primary insomnia completed the trial. Quality of sleep was significantly improved with melatonin supplements (-22.5 vs. -16.5 mm, P=0.047). Morning alertness was improved (-15.7 vs. -6.8 mm, P<0.002) compared with placebo. Quality of sleep and morning alertness were significantly correlated (R=0.77, P<0.001) suggesting that the restorative value of sleep was beneficially affected.33
Effects of exogenous melatonin on sleep: a meta-analysis.
A meta-analysis evaluated the effects of exogenous melatonin on sleep and included English language articles from 1980 to 2003. Seventeen studies were included in the review (a total of 284 participants). Melatonin treatment significantly reduced sleep onset latency by 4.0 min (95% CI 2.5 to 5.4 min); increased sleep efficiency by 2.2% (95% CI 0.2 to 4.2), and increased total sleep duration by 12.8 min (95% CI 2.9 to 22.8 min). Including only trials with healthy subjects or subjects with only insomnia (15 trials), sleep onset results were reduced to 3.9 min (95% CI 2.5 to 5.4 min); sleep efficiency increased to 3.1% (95% CI 0.7 to 5.5); and sleep duration increased to 13.7 min (95% CI 3.1 to 24.3 min). The results of this meta-analysis support the conclusion that melatonin supplements improve sleep for the populations studied.34
Physiological levels of melatonin contribute to the antioxidant capacity of human serum.
During nighttime, both melatonin and total antioxidant status (TAS) decrease to basal daytime values and with aging, day to night differences in melatonin and TAS change. A study on healthy volunteers from ages 2 to 89 years examined whether physiological concentrations of melatonin contribute to the antioxidant capacity of human serum. Results showed physiological melatonin concentrations in human serum, especially at night, exhibited significant antioxidative properties.35
Therapeutic effect of melatonin in patients with functional dyspepsia.
The antioxidant activities of melatonin may help to alleviate symptoms of ulcerlike dyspepsia. A placebo-controlled trial with 60 participants aged 19 to 39 years with functional dyspepsia investigated the effects of melatonin. Participants did not have Helicobacter pylori infection. Subjects consumed 5 mg melatonin or placebo daily in the evening for 12 weeks. In the melatonin group, symptoms completely subsided after 12 weeks for 56.6% of the participants (17 people). Symptoms were improved for 9 participants in the melatonin group (30.0%). In contrast, participants consuming the placebo did not experience improvement of symptoms (93.3% maintained current level of symptoms). Prior infection with H. pylori was found to diminish efficacy of melatonin. The results of this study suggest that melatonin may be beneficial for ulcerlike dyspepsia for people without H. pylori infection. Further studies are needed to confirm these benefits.36
Melatonin supplementation ameliorates oxidative stress and inflammatory signaling induced by strenuous exercise in adult human males.
The effects of melatonin supplements on oxidative stress and inflammation were evaluated in a placebo-controlled, parallel-design, single-blind trial. Twenty amateur athletes participated in the trial; participants were divided into two groups. One group received five 3 mg melatonin capsules which were taken as follows: one capsule 2 days before the test with dinner, three capsules on the previous day (breakfast, lunch, and dinner), one capsule the same day of the run, 1 hr before beginning the physical test. The placebo group also received five capsules which were taken in the same manner. All participants completed a constant-run physical test that was 50 km with almost 2800 m in elevation change (increase). Exercise significantly increased TNF-á, blood IL-6, IL-1ra, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), urinary isoprostane levels, and indicated an increase in oxidative stress and inflammation. Lipid peroxidation was decreased and antioxidative enzyme activities were increased in the melatonin supplemented group compared to the control group. Melatonin supplements taken prior to strenuous exercise reduced muscle damage in this study.37
Effects of melatonin in perimenopausal and menopausal women: a randomized placebo controlled study.
A study with perimenopausal and menopausal women ages 42 to 62 took 3 mg of melatonin or placebo at bedtime for 3 and 6 months. Melatonin produced a significant diminution of luteotropic hormone in the women aged 43 to 49, but no effect was seen in the 52 to 62 year old women. The women receiving melatonin reported a general improvement in mood, a significant mitigation of depression and a recovery of pituitary and thyroid functions. Overall, researchers concluded that this showed a more juvenile pattern of regulation.38
A preliminary study of melatonin in irritable bowel syndrome.
A small study investigated the effects of melatonin on symptoms, extracolonic symptoms, and quality of life (QOL) for people with irritable bowel syndrome (IBS). Eighteen people with IBS, aged 18 to 65 years, participated in the eight week study. Participants were randomly assigned to receive 3 mg melatonin or a placebo daily at bedtime. Overall IBS scores, extracolonic IBS scores, and QOL scores were assessed every two weeks during the trial and then at 16, 24, and 48 weeks after the end of the study period. Melatonin significantly improved overall IBS scores compared to placebo (45% vs. 16.66%, P<0.05). The posttreatment extracolonic IBS score was also significantly lower when compared to the placebo group (49.16% to 13.88%, P<0.05). The overall improvement in QOL score was greater in the melatonin group than the placebo group (43.63% vs. 14.64%, respectively). This preliminary study confirms that melatonin may help improve symptoms for people with irritable bowel syndrome.39
Melatonin improves bowel symptoms in female patients with irritable bowel syndrome: a double-blind placebo-controlled study.
A double-blind, placebo-controlled, crossover design study investigated the efficacy of melatonin for improving symptoms of irritable bowel syndrome (IBS). Seventeen women with IBS participated in the trial. Participants consumed 3 mg melatonin or a placebo daily at bedtime. Subjects were randomized to receive melatonin or the placebo for eight weeks followed by a four week washout period and finally a second eight week trial with melatonin/placebo assignment reversed. Mean IBS scores were significantly improved after treatment with melatonin (3.9 +/- 2.6) relative to placebo (1.3 +/- 4.0, P=0.037). The percentage of subjects achieving mild-to-excellent improvement in IBS symptoms (percent response rate) was greater in the melatonin group (88% vs. 47%, P=0.04). The results of this small trial indicate that melatonin may be beneficial for symptoms of IBS.40
Melatonin improves abdominal pain in irritable bowel syndrome patients who have sleep disturbances: a randomised, double blind, placebo controlled study.
A randomized, double-blind, placebo-controlled trial investigated the efficacy of melatonin for symptoms of irritable bowel syndrome (IBS). Forty people with IBS participated in the trial. Participants were randomly assigned to receive 3 mg melatonin or a placebo daily at bedtime for two weeks. Melatonin supplements significantly decreased mean abdominal pain score, compared to placebo (2.35 vs. 0.70, p<0.001). Melatonin also significantly increased mean rectal pain threshold versus placebo (8.9 vs. -1.2 mmHg, p<0.01). Although melatonin improved symptoms of IBS in this trial, sleep disturbances were not improved. No changes in total sleep time, sleep latency, sleep efficiency, sleep onset latency, arousals, duration of stages 1-4, rapid eye movement (REM) sleep, and REM onset latency were detected. This trial suggests that effects of melatonin in IBS symptoms do not derive from alterations in sleep from melatonin. Further trials are needed to elucidate the mechanisms involved.41
A prospective, open-label trial investigated the effects of melatonin on tinnitus. Twenty-four people with tinnitus participated in the trial. Participants consumed 3 mg melatonin daily for four weeks of observation. During the trial, tinnitus handicap inventory (THI) score improved. Improvement from baseline was noted over four weeks, and over eight weeks. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality during the study. PSQI significantly decreased between weeks 0 and 4 (P<0.0001), and between weeks 0 and 8 (P=0.0003). The changes in PSQI and THI scores were significantly associated. In this trial, melatonin use was associated with improvements in tinnitus and sleep quality. Further studies are necessary to confirm these results.42
Daily nighttime melatonin reduces blood pressure in male patients with essential hypertension.
A randomized, double-blind, placebo-controlled crossover trial investigated the effects of acute (single dose) or repeated (daily for 3 weeks) melatonin supplements on sleep and blood pressure. Sixteen men with untreated essential hypertension participated in the trial. The acute trial investigated changes after a single 2.5 mg melatonin supplement. The repeated trial investigated changes after 3 weeks of 2.5 mg melatonin taken daily on hour before sleep. The single dose had no affect on sleep or blood pressure. Repeated use of melatonin for 3 weeks decreased systolic and diastolic blood pressure by 6 and 4 mmHg, respectively. No change in heart rate was detected. Day-night amplitudes of the rhythms in systolic blood pressure were increased by 15% and diastolic blood pressures were increased by 25%. Repeated use of melatonin also improved sleep, however changes in blood pressure were not associated with changes in sleep. Larger studies are needed to confirm these results.43
Prolonged melatonin administration decreases nocturnal blood presure in women.
A randomized, double-blind, crossover design study evaluated the effects of melatonin supplements on nocturnal blood pressure in women with normal blood pressure or with treated essential hypertension. Eighteen women aged 47 to 63 years participated in the trial. Participants consumed a daily slow-release melatonin supplement (3 mg) or a placebo one hour prior to bedtime for three weeks. All participants then crossed over to the other treatment for an additional three weeks. Melatonin was not found to alter daytime blood pressure compared to placebo. Nocturnal systolic, diastolic, and mean blood pressures were significantly decreased with the melatonin supplements compared to placebo (respectively, -3.77 ± 1.7 mmHg, P=0.0423; -3.63 ± 1.3 mmHg, P=0.0153; -3.71 ± 1.3, P=0.013). Heart rate was not modified. The results of this trial suggest that melatonin supplements significantly decrease nocturnal blood pressure for women with normal blood pressure or treated hypertension.6
Melatonin differentially affects vascular blood flow in humans.
Blood flow, blood pressure, and heart rate were monitored in ten healthy subjects aged 29 ± 1 year 45 minutes after consumption of a 3 mg melatonin supplement or a placebo. Participants repeated the trial with the other substance at least two days later at the same time of day. Heart rate and mean arterial pressure were not altered by melatonin compared to placebo. Melatonin reduced renal blood flow velocity and renal vascular conductance compared with placebo (40.5 ± 2.9 vs. 45.4 ± 1.5 cm/s; 0.47 ± 0.02 vs. 0.54 ± 0.01 /mmHg, respectively). Forearm blood flow and forearm vascular conductance were greater with melatonin compared with placebo (2.4 ± 0.02 vs. 1.9 ± 0.1 mL/100mL/min; 0.029 ± 0.003 vs. 0.023 ± 0.002 arbitrary units, respectively). Cerebral blood flow measurements were not altered. The results of this trial indicate that melatonin differentially affects vascular blood flow in human renal, forearm, and cerebral beds.9
The dietary supplement information contained on this site has been compiled from published sources thought to be reliable, but it cannot be guaranteed. Efforts have been made to assure this information is accurate and current. However, some of this information may be purported or outdated due to ongoing research or discoveries. The authors, editors and publishers cannot accept responsibility for errors or omissions or for any consequences from applications of the information in this site and make no warranty, expressed or implied, with respect to the contents herein.