Milk is known to contain many important nutrients like protein, calcium, vitamin D, and vitamin B12. However, one compound that milk is not known to contain in significant amounts is melatonin. Melatonin is a hormone that helps regulate sleep cycles and is typically synthesized in the pineal gland when it gets dark outside. This leads to some common questions around whether drinking milk at night can help promote sleep due to melatonin content. In this comprehensive article, we’ll analyze if milk contains melatonin and how much is present if any.
What is Melatonin?
Melatonin is a hormone synthesized and secreted by the pineal gland, a small endocrine gland located in the brain. Melatonin helps regulate circadian rhythms and the sleep-wake cycle. Melatonin production increases when it’s dark and decreases when there is light. This daily cycle helps entrain the body’s internal clock and signals the appropriate times for being awake and sleeping. Some key facts about melatonin:
- Melatonin is produced from the amino acid tryptophan.
- Melatonin helps induce drowsiness before sleep and regulates the sleep cycle.
- Melatonin production declines with age which can lead to disrupted sleep in the elderly.
- Melatonin is available as an over-the-counter oral supplement.
- Taking melatonin supplements at the right time can help with jet lag and shift work.
Overall, melatonin acts as a regulator of sleep-wake cycles in both circadian rhythm and seasonal responses to changes in day length. Understanding the role melatonin plays in sleep is key background when analyzing whether milk contains meaningful amounts.
Melatonin Content in Milk
Research studies that have analyzed the melatonin content in cow’s milk have found that it contains only trace amounts, ranging from 2-4 picograms/mL. For reference, a typical 3 mg dose of supplemental melatonin contains 3,000,000 picograms. So the melatonin concentrations present in milk are negligible.
However, even though melatonin concentrations are low, milk contains moderate levels of tryptophan. Tryptophan is an essential amino acid and serves as the precursor from which melatonin is synthesized in the body. An 8 oz glass of milk contains around 250-350mg of tryptophan. Therefore, while not a direct source, milk can support your body’s own melatonin synthesis through providing tryptophan.
Research also shows that nighttime warmth from milk may support sleepiness through indirect means like soothing the gastrointestinal system. But the actual melatonin content is not a factor. This is likely why milk is often recommended as a sleep-promoting beverage.
Melatonin Levels in Human vs. Cow’s Milk
Human breast milk, unlike cow’s milk, does contain measurable amounts of melatonin. Melatonin concentrations in human breast milk are estimated to be around 3-4 ng/mL, several orders of magnitude higher than cow’s milk.
Nighttime breast milk also contains more melatonin than daytime milk. This circadian rhythm variation provides a way for breastfeeding mothers to communicate day/night cycles to infants and regulate infant sleep patterns.
So while human breast milk does have meaningful melatonin content, cow’s milk has negligible amounts. However, some tryptophan is present which can support endogenous melatonin production.
Factors That Impact Melatonin Levels in Milk
Since melatonin levels are low but measurable in milk, especially human breast milk, it’s worth understanding what factors impact concentrations:
Time of Day
As mentioned, both human and cow milk have circadian variations in melatonin content. Levels are higher during nighttime milkings compared to daytime. This mirrors natural melatonin production.
Breed & Feed
Melatonin levels can vary somewhat between breeds of dairy cows. But a more significant factor is the type of feed cows consume. Cows fed high tryptophan diets produce milk with higher melatonin content. Pasture grazing compared to indoor feeding also may alter levels.
Season
Research indicates cows produce milk with higher melatonin levels in the winter. This may be an adaptive response to seasonal changes in daylight patterns.
Additives
Some studies have experimented with adding melatonin supplements directly to cow’s milk. This can spike melatonin concentrations closer to levels found in human breast milk, though the effects are temporary as melatonin decays.
Processing
Processing methods like pasteurization, homogenization, and fat content adjustments do not appear to significantly impact innate melatonin levels already present in milk. However, most processing will break down any additives like supplemental melatonin.
So while dietary and environmental factors can alter milk melatonin content to some degree, concentrations remain trace in the context of sleep-promoting doses.
Potential Effects of Melatonin in Milk on Sleep
Given the very low amounts of melatonin naturally present in cow’s milk, it likely does not directly contribute to sleepiness through melatonin content alone. However, some secondary effects associated with warm milk before bed may help support sleep:
Tryptophan Content
As mentioned, milk provides a moderate amount of the precursor tryptophan per serving which can help boost natural melatonin synthesis. Tryptophan requirements for melatonin production are higher in the evening.
Soothing Warmth
The warmth of heated milk can help promote soothing feelings that are sleep-inducing. This may work partially through relaxing the digestive system.
Positive Associations
Culturally, warm milk is associated with bedtime routines for children. Positive routines and wind-down time help signal the brain and body that sleep is approaching.
So while not directly attributable to melatonin, milk may promote sleepiness through secondary pathways like tryptophan intake, soothing warmth, and positive routine associations.
How Much Melatonin is Needed For Sleep
Since cow’s milk contains only trace amounts of melatonin, it’s worth understanding how much is generally needed to promote sleep.
Research on melatonin supplements finds that doses between 1-10 mg are effective for sleep. To put this into context:
- Typical melatonin supplements range from 1-5mg.
- Released melatonin peaks at 200 pg/ml of blood.
- 1-3 mg doses result in 10-100 times normal levels.
- Low doses around 0.3mg may be equally effective.
So while melatonin concentrations in the 1-3 mg range are thought to help induce sleep, typical cow’s milk contains around 0.002 mg. This is far below an amount that would directly contribute melatonin-induced sleepiness.
Summary of Melatonin Dosing for Sleep
| Dose | Effect on Sleep |
|---|---|
| 0.3 – 1 mg | May help induce drowsiness |
| 1 – 5 mg | Modulates sleep cycle |
| 10+ mg | Higher doses not necessarily more effective |
As this table summarizes, supplemental melatonin in the 1-5 mg range can help regulate sleep cycles and induce drowsiness. Cow’s milk contains melatonin in the picogram (trillionth of a gram) range, far below sleep-promoting doses.
Other Foods and Drinks with Melatonin
While cow’s milk is not a meaningful source of melatonin, some other foods and beverages contain higher amounts:
Tart Cherry Juice
Tart cherry juice provides around 85 micrograms melatonin per 8 oz serving. This is significantly more than milk but still lower than supplement doses.
Bananas
Bananas contain around 5 nanograms melatonin per gram. So a medium banana has around 200 ng. Not a significant source but some presence.
Walnuts
Walnuts contain traces of melatonin in the range of 0.1-1.5 nanograms per gram. Better than milk but nowhere near supplemental doses.
Tomatoes
Research indicates tomatoes have around 1-5 nanograms/gram of melatonin. The red pigment lycopene may also promote sleep.
Tart Cherries
Tart cherries contain melatonin levels similar to tomatoes. They may also promote sleep through other compounds.
Pistachios
Pistachios contain trace melatonin in amounts ranging from 0.1-2 nanograms per nut. Interesting for comparison but not a significant source.
White Rice
While not thought of for sleep-promoting properties, white rice contains modest amounts of melatonin in the range of 20-80 picograms/gram.
So in summary, while no food rivals concentrated supplements, some fruits and nuts contain low but measurable melatonin levels. Cow’s milk’s trace amounts are negligible by comparison.
Should You Drink Milk for the Melatonin?
Based on the very low concentrations present, drinking milk solely for the melatonin content is not likely to be effective for improving sleep. However, some broader factors make warm milk a reasonable sleep-supporting beverage:
- The tryptophan content may support melatonin synthesis.
- Warm milk promotes relaxation and comfort pre-sleep.
- Routine and positive associations reinforce circadian signals.
- Easy digestibility compared to larger meals.
- Avoid exceeding 8 oz to limit digestive discomfort.
So while melatonin levels themselves are negligible, milk can be part of an effective bedtime routine given its other attributes. Just don’t expect pronounced melatonin-induced drowsiness given the trace amounts present.
Should You Add Melatonin to Milk?
Since the melatonin content of plain cow’s milk is low, some may wonder if adding melatonin drops or powder can make it more sleep-promoting.
There’s limited research in this area, but a few considerations on adding melatonin:
- Can spike melatonin levels closer to concentrations in human breast milk.
- Easy way to ingest melatonin, especially for children.
- Most melatonin degrades during processing and pasteurization.
- May impart an unpleasant flavor.
- Difficult to determine exact dosing.
Given that melatonin breaks down readily and dosing is complicated, the best approach is likely taking supplements separately. But if adding, restrict to small doses and avoid extremely hot milk which degrades melatonin. Discuss with your doctor before using as a sleep aid, especially for children.
Melatonin Milk: Recap and Key Takeaways
To recap the key points on melatonin content in cow’s milk:
- Cow’s milk contains only trace amounts of melatonin in the picogram/mL range.
- Human breast milk has higher melatonin levels, especially at night.
- Melatonin concentrations in milk are far below typical supplemental doses of 1-5mg.
- Milk provides tryptophan which supports natural melatonin synthesis.
- Warm milk and positive routines can help induce drowsiness and sleep.
- Addition of melatonin to milk is possible but not widely recommended or researched.
So in summary, milk is not a significant source of melatonin, but remains a reasonable traditional sleep-promoting drink given its other attributes. It’s just not the melatonin itself that makes milk an effective sleep aid.
Conclusion
Based on the available research, cow’s milk contains only negligible amounts of melatonin in the low picogram per milliliter range. Concentrations are far below typical melatonin supplement doses used for sleep regulation and induction. However, milk can still be beneficial before bed through tryptophan intake, associations with bedtime routines, and soothing effects – but not because of pronounced melatonin levels. While addition of melatonin to milk can increase concentrations, taking regular melatonin supplements as directed is likely a simpler and more effective strategy. So in conclusion, the answer to whether milk contains significant melatonin is clearly no, but drinking a warm glass of milk before bed can still be part of an effective sleep routine through its other attributes.