Chronic insomnia (difficulty falling asleep, maintaining sleep, or non-restorative sleep for at least 3 nights per week for over 3 months) affects 10-15% of the adult population, or 30-40% when including transient insomnia. The health consequences of chronic insomnia are well-documented and serious: increased cardiovascular risk, cognitive impairment, reduced immunity, worsening of all psychiatric conditions, and increased perceived pain. The first-line therapeutic approach for chronic insomnia is CBT-I (Cognitive Behavioral Therapy for Insomnia), which is superior to medications in the long term. Nutrition is one of the modifiable behavioral elements that influences sleep in a documented way.

The tryptophan-serotonin-melatonin pathway: the key mechanism

Tryptophan is the amino acid precursor of serotonin, which in turn is the precursor of melatonin (the sleep hormone). The biosynthetic chain requires: tryptophan (essential amino acid: must come from diet), vitamin B6 and zinc as cofactors, and carbohydrates (which facilitate tryptophan transport to the brain by reducing competing amino acids). Foods rich in tryptophan: turkey (often cited, but not exceptionally rich compared to others: about 290 mg per 100 g), eggs (195 mg/100g), pumpkin seeds (576 mg/100g: the richest easily available source), aged cheese (Parmesan: 490 mg/100g), salmon (330 mg/100g), whole milk (46 mg/100 ml: small in quantity but traditionally used before sleep for relaxation). Warm milk before bed: the classic grandmother's remedy has partial basis: milk contains tryptophan but in non-exceptional quantities. The main effect of warm milk could be the conditioned response (the calming ritual), the heat that reduces body temperature in the following hours (which promotes sleep), and the small tryptophan component in a context of light carbohydrate intake (lactose facilitates tryptophan transport). Nothing magical: but it works for many people as part of a calming evening routine.

Foods rich in melatonin: the evidence

Some foods contain melatonin directly (not just precursors). Tart cherries (Montmorency cherries): the most studied food source of melatonin. A study by Howatson et al. (2012, European Journal of Nutrition) showed that tart cherry juice (240 ml twice daily for 7 days) increased urinary melatonin levels and improved sleep duration by 25 minutes and sleep quality. The concentration of melatonin in tart cherries is 13-17 ng/g. In Italy, tart cherries (Amarene, Marasche) are available in season and as juice or compote. Kiwi: a study by Lin et al. (2011, Asia Pacific Journal of Clinical Nutrition) on 24 adults with sleep disorders showed that eating 2 kiwis one hour before bed for 4 weeks significantly improved sleep onset (by 35%), total sleep duration (by 13.4%), and sleep efficiency. Proposed mechanisms: serotonin (kiwis are relatively rich in it), vitamin C and folate (antioxidants), vitamin E. Walnuts: contain direct melatonin (3-4 ng/g), tryptophan, magnesium, and omega-3 ALA fatty acids. Studies in animal models show increased evening melatonin levels with walnut consumption. Raisins, tomatoes, peppers: contain melatonin in small quantities. Not at the level of tart cherries but contribute to the overall pool.

The impact of nocturnal blood sugar on sleep

Blood sugar stability during the night significantly influences sleep quality. Nocturnal hypoglycemia (blood sugar dropping too low during sleep) activates the sympathetic nervous system and can cause awakenings, sweating, and feelings of agitation. Even in non-diabetic people, a dinner very low in carbohydrates followed by a long overnight fast can lead to a slight blood sugar drop in the early morning hours with early morning awakening. Conversely, a dinner too rich in simple carbohydrates (white pizza, sweets, alcohol) causes a blood sugar spike followed by a rebound that can disturb sleep in the first part of the night. The optimal dinner for sleep: a balanced meal (complex carbohydrates + protein + vegetables) in moderate quantities, at least 2-3 hours before bed. Complex carbohydrates (whole wheat pasta al dente, rice, potatoes) with a protein source (legumes, fish, eggs, low-fat dairy) support nighttime serotonin and melatonin production without creating blood sugar instability. The pre-sleep snack (if necessary): for those who wake frequently or have nighttime hunger, a small low-glycemic snack is better than nothing: a handful of walnuts, a tablespoon of almond butter, a piece of cheese. Proteins and fats stabilize blood sugar longer than carbohydrates alone.

Caffeine, alcohol, and sleep: how much and when

Caffeine and sleep: caffeine has a half-life of 5-6 hours (6-12 hours in people with slow CYP1A2 metabolism). A shot of espresso (80 mg of caffeine) at 2 PM still has 40 mg active at 8 PM in the average metabolizer. In people with slow metabolism: it can still have 40 mg active at 10-11 PM. The practical rule: don't consume caffeine after 1-2 PM for people with insomnia. Reduce total caffeine to no more than 200 mg/day (2 espressos). Lesser-known sources of caffeine: black tea (50-80 mg per cup), green tea (25-50 mg per cup), mate (85 mg per cup), dark chocolate (23 mg per 30 g), energy drinks (80-160 mg per can), cola (34 mg per 350 ml). Alcohol and sleep: alcohol is a sedative that facilitates falling asleep but structurally worsens sleep quality. It increases deep slow-wave sleep in the first half of the night but reduces REM sleep (restorative and dream sleep) in the second half. The net effect is more fragmented, lighter sleep with early morning awakening and a feeling of not having rested. The practical rule: eliminate evening alcohol or limit it to 1 unit (a glass of wine) with dinner, without getting any closer to bedtime. Those suffering from chronic insomnia: the goal is to completely eliminate evening alcohol.

Supplements for insomnia with scientific basis

Melatonin: the supplement with the strongest evidence. Effective especially for: jet lag (circadian rhythm shift), advanced sleep phase insomnia (difficulty falling asleep before midnight-1 AM) in the elderly, shift work insomnia. Dosage: 0.5-3 mg one hour before the desired sleep time. Less is better: low doses (0.5-1 mg) are often as effective as high doses and produce less rhythm dependence. Melatonin is not a sedative: it doesn't directly induce sleep but shifts the circadian rhythm. It's not effective for all types of insomnia. In Italy it's available as a supplement (up to 1 mg) without prescription; higher doses require a medical prescription. Magnesium glycinate or threonate: magnesium has relaxing effects on muscles and the nervous system. Magnesium threonate (Magnesium L-Threonate) is the form with the best blood-brain barrier penetration, with studies showing improved sleep in the elderly (Liu et al., 2023). Dosage: 200-400 mg in the evening. Valerian: meta-analyses show modest subjective improvement in sleep quality. The effect is more consistent with prolonged use (2-4 weeks) compared to a single dose. Proposed mechanism: GABAergic action. L-theanine (100-200 mg): improves subjective sleep quality and the feeling of rest upon waking in controlled studies. Mechanism: promotion of brain alpha waves, reduction of sympathetic excitation. Safe, without direct sedative effects, suitable even for those who need to drive in the morning.

The dietary protocol for sleep: weekly summary

A structured eating plan to support sleep. Every day: stop consuming caffeine by 1-2 PM, balanced dinner (complex carbohydrates + protein + vegetables) finished 2-3 hours before bed, avoid alcohol or limit it to a glass with dinner (never close to sleep time), 2 kiwis one hour before bed (or a handful of tart cherries or a glass of tart cherry juice if available), a handful of walnuts as an evening snack (source of melatonin, tryptophan, and magnesium), 200-400 mg of magnesium glycinate with dinner (if you prefer a supplemental approach). Several times a week: fatty fish at dinner (salmon, sardines, mackerel: omega-3 + vitamin D + tryptophan), warm milk with honey as an evening ritual if you like, chamomile and/or lemon balm tea after dinner. Avoid: heavy meals in the 2 hours before bed, simple sugars in the evening (cookies, sweets, ice cream), smoking (nicotine is a stimulant with a half-life similar to caffeine), bright screens in the 30-60 minutes before bed (blue light inhibits melatonin). This protocol does not replace CBT-I in structural insomnias: but optimizing nutrition removes dietary barriers to sleep that often worsen underlying difficulties.