Melatonin is an indolamine hormone secreted by the pineal gland, a small endocrine gland localized within the brain. Melatonin production and secretion are synchronized by the light-dark transitions perceived by the eyes. During the night, melatonin concentration in the blood is elevated, which favors sleep and induces nighttime physiological functions, while melatonin secretion is inhibited by the blue light component of natural daylight, which promotes wakefulness.
Melatonin has anti-inflammatory properties and acts as an immune modulator. It also plays a role in the regulation of the circadian rhythm [1], possesses anti-tumor properties [2], and presents beneficial effects on glycemia [3]. Therefore, enhancing the production of melatonin may positively impact health.
In this article, we'll be exploring 4 ways to naturally increase your melatonin levels through some dietary and lifestyle changes, whether it be lessening exposure to room light, eating foods like eggs and fish more often, or having one less cup of coffee!
1. Avoid artificial light at night
As the body’s circadian clock is synchronized by the light-dark transitions, it can be disturbed by artificial lighting, especially at night when it's dark outside [4].
Melatonin secretion is highly sensitive to light. The exposure of rats to dim light (2 lux) was able to reduce the enzyme synthesizing melatonin from serotonin by 50% [5]. In humans, Lewy and colleagues demonstrated that bright artificial light (greater than 2500 lux) suppressed melatonin secretion in six healthy subjects [2]. Sitting in a room illuminated by fluorescent lamps can deliver up to 800 biolux, which suppresses melatonin secretion by 65% [6].
Various studies have shown the negative impact of light exposure at night on sleep, including greater difficulties in falling asleep, decreased sleep time, poorer sleep quality with reduced slow-wave sleep, and difficulties in waking up [7]. One night of exposure to light can alter cardiovascular and metabolic responses [8], and sleeping with light might favor weight gain and obesity [9].
2. Lessen screen time and artificial blue light
Blue light is naturally found in sunlight, and its absence prompts the pineal gland to secrete melatonin. Electronic devices (smartphones, computer screens, or televisions) also emit blue light and can therefore interfere with melatonin production [10].
In humans, exposure to short-wavelength blue light between 446 and 477 nm suppresses melatonin production more effectively than longer-wavelength light [11]. Exposure to blue light has been shown to suppress melatonin levels more effectively than green light [12], with the magnitude of this effect increasing over time [13].
Oh and colleagues measured the decrease in nocturnal melatonin levels in individuals exposed to their smartphones in a bright room at night. They found a reduction of up to 36.1% in nocturnal melatonin levels. Similarly, nighttime exposure to 470 nm blue LED suppressed melatonin levels by 60% [6]. Another study, conducted by Wood and colleagues, exposed 13 volunteers for two hours to tablet screens or tablets with blue LEDs and showed that their nocturnal melatonin levels were suppressed by 20 and 65%, respectively [14]. Therefore, avoiding artificial light, particularly blue light in the evening, can naturally increase melatonin levels [10].
3. Decrease your caffeine intake
Caffeine, a stimulant molecule present in coffee, is well-known to disrupt sleep, and this effect is, at least partly, caused by melatonin-reduced secretion [15]. As an adenosine antagonist (inhibitor), caffeine was shown to reduce melatonin levels in humans on the day of consumption [16].
Burke and colleagues demonstrated that caffeine primarily affects human cellular circadian clocks via the adenosine A1 receptor (A1R) in a cyclic AMP-dependent mechanism in human U2OS cells [17]. They conducted 49-day circadian phase-shifting trials involving five healthy participants. The circadian phase was assessed under constant routine conditions on the day before and after participants were exposed to four randomly ordered interventions: dim-light placebo, dim-light caffeine, bright-light placebo, and bright-light caffeine. Caffeine was administered three hours before participants’ habitual bedtime, while light exposure started at habitual bedtime for three hours. Results showed that evening caffeine administration induced a phase delay approximately half the magnitude of the phase shift caused by evening exposure to bright light [17]. Their findings demonstrate that caffeine influences human circadian timing by affecting melatonin and that lessening caffeine intake may increase melatonin production.
4. Consume foods high in melatonin
Considering the potential health benefits of melatonin, multiple studies have explored its oral bioavailability. In one study involving 12 healthy volunteers, both 2 and 4 mg oral doses of melatonin showed poor bioavailability, estimated at approximately 15% [18]. In another study involving 12 young volunteers, a 250 μg oral dose of D7 melatonin showed great bioavailability variability ranging from 1 to 37%, with higher rates observed in women compared to men. Additionally, the melatonin release from oral solutions was rapid and associated with short half-life values (time to eliminate half of the exogenous melatonin from blood) in males (36 ± 2 min) and females (41 ± 10 min) [19]. Finally, a last study involving seven healthy males who received 3 mg of oral melatonin showed a marked increase in serum melatonin (3561 ± 1201 pg/mL), with sustained elevated levels observed up to 4 h post-ingestion [20]. These findings underscore the complexity and variability associated with oral melatonin supplements and their administration; nevertheless, other studies investigated its bioavailability from dietary sources.
Reiter and colleagues found that melatonin is present in walnuts at a concentration of 3.5 ± 1.0 ng/g and that feeding walnuts to rats increased blood melatonin levels compared to rats fed a control diet. This increase in melatonin was associated with enhanced antioxidant capacity in the blood, as indicated by higher trolox equivalent antioxidant capacity and ferric-reducing ability of serum values [21]. Sae-Teaw and colleagues conducted a crossover study involving 12 healthy volunteers and examined the impact of fruits or fruit juice containing melatonin on serum melatonin concentration and antioxidant status. Participants consumed orange or pineapple juice, or two whole bananas, before measuring serum melatonin. The highest serum melatonin concentrations were observed at 120 min after fruit consumption, with significant increases observed for pineapple (146 versus 48 pg/mL, P = 0.002), orange (151 versus 40 pg/mL, P = 0.005), and banana (140 versus 32 pg/mL, P = 0.008). Serum antioxidant capacity, assessed by ferric reducing antioxidant power (FRAP) and oxygen radical antioxidant capacity (ORAC) assays, also significantly increased following fruit consumption. Finally, serum FRAP and ORAC values correlated strongly with serum melatonin concentration for all three fruits, suggesting that tropical fruit consumption enhances serum melatonin levels and antioxidant capacity in healthy volunteers in a dose-dependent manner [22].
Given melatonin bioactivities, its concentration in many different foods has been tested in the past decades and is a highly variable parameter. The melatonin content is higher in eggs and fish than in meat. For plants, the primary sources of melatonin content are found in nuts, cereals, germinated legumes, and seeds. Mushrooms are also rich in melatonin [23]. The Mediterranean diet, well-known to have beneficial effects on human health, is particularly rich in antioxidants, such as melatonin. Tomatoes, wine, nuts, and olive oil —found in the Mediterranean diet — are known sources of melatonin, with certain varieties exhibiting particularly high melatonin content [24].
Conclusion
Exposure to natural light, particularly sunlight in the morning, helps regulate the body's circadian rhythm and enhances melatonin production at night. Similarly, reducing exposure to artificial light, especially blue light from electronic devices, and avoiding caffeine can significantly improve melatonin levels. Additionally, consuming melatonin-rich foods may boost melatonin blood levels after ingestion, although further studies are needed to fully understand them.
If you’d like to use melatonin for what it’s best known for (i.e., helping with the timing of your circadian rhythms and improving your sleep), then give Tro Zzz a try! It’s our buccal troche formulated for sleep that has melatonin as one of its main ingredients to help you fall and stay asleep and wake up feeling refreshed.
References
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