The Science Behind Melatonin and Milk
Melatonin, commonly known as the “sleep hormone,” plays a key role in regulating the body's sleep-wake cycle. Its production is heavily influenced by light, increasing in darkness and decreasing in light, which is why melatonin levels in milk fluctuate throughout the day. Tryptophan, an amino acid found in milk, is a precursor to melatonin and serotonin, further linking dairy consumption to sleep support.
Human Breast Milk: A Time-Sensitive Sleep Aid
Human breast milk contains melatonin, which is particularly important for infants whose own melatonin production is not yet fully developed. Melatonin levels in breast milk peak at night, providing a natural signal that may help infants establish their own circadian rhythms. Studies indicate that breast milk from night feedings can have significantly more melatonin than milk from daytime feedings. This has led to suggestions for mothers to note the time milk is expressed to align with an infant's needs. Research also shows that milk from mothers of preterm infants may have higher melatonin levels compared to milk from mothers of full-term babies. Factors such as maternal health and light exposure can influence these levels.
Cow's Milk: "Night Milk" for Sleep Promotion
Cow's milk also exhibits a circadian pattern of melatonin, with the highest concentrations found in milk collected during the night. This has led to the production of specialized "night milk" in some regions. Research suggests that night milk has higher melatonin levels than milk collected during the day and may have sedative and anxiety-reducing effects, as shown in animal studies. Early human studies suggest that consuming melatonin-rich night milk could improve sleep quality in older adults. Processing methods like UHT do not appear to significantly reduce the melatonin content in milk.
Comparing Different Types of Milk and Melatonin Content
| Feature | Human Breast Milk (Night) | Cow's Milk (Night) | Cow's Milk (Day) |
|---|---|---|---|
| Melatonin Content | Very high; can be up to 10x daytime levels | Higher than daytime milk; influenced by milking time | Significantly lower concentration |
| Primary Beneficiary | Breastfed infants, especially preemies | General consumers, particularly those seeking a natural sleep aid | All consumers |
| Circadian Alignment | Essential for infant's developing circadian rhythm | Depends on milking schedule; 'night milk' is explicitly timed | Not aligned for sleep-promoting effects |
| Impact of Light | Maternal light exposure directly affects levels | Artificial light during milking can suppress melatonin levels | Light exposure inhibits production |
| Commercial Availability | Not commercially available, but pumping practices can leverage time-of-day | Available as specialized products in some markets (e.g., Lullaby Milk, Dreamerz) | Widely available |
Plant-Based Milks and Melatonin
Plant-based milk alternatives such as almond, soy, or oat milk do not naturally contain melatonin, as it is a hormone produced by mammals. While some nuts like pistachios and almonds contain compounds that may support sleep, such as melatonin and magnesium, these are not inherent to plant-based milk products. Fortification with vitamins and minerals is common, but it does not include melatonin. Therefore, the sleep benefits often associated with warm plant milk are likely due to the psychological comfort of the routine rather than melatonin content.
Conclusion
Milk naturally contains melatonin, with concentrations peaking during the night. This is observed in both human breast milk, where it helps establish infant sleep patterns, and cow's milk, leading to the development of "night milk" products. Plant-based milk alternatives do not contain natural melatonin. While the melatonin in milk is a small amount compared to supplements, incorporating night-time dairy milk into your routine or simply enjoying a warm drink may contribute to better sleep. For further information on foods that aid sleep, the Sleep Foundation is a valuable resource.
