Apetito (deficiente)

5-HTP is the immediate biochemical precursor to serotonin, which is subsequently converted to melatonin in the pineal gland. Supplemental 5-HTP raises serotonin and downstream melatonin levels, supporting circadian rhythm entrainment. Animal studies confirm restoration of slow-wave sleep via this pathway, and a 2024 RCT in Clinical Nutrition examined 5-HTP supplementation on sleep quality in older adults.

Apigenin, a flavone concentrated in chamomile and other plants, acts as a partial agonist at the GABA-A benzodiazepine binding site to promote sedation relevant to sleep-wake cycle regulation. A 2025 authoritative Nutrition Reviews narrative review specifically identified apigenin-containing chamomile among nutraceuticals with evidence for improving circadian rhythm and sleep disturbance outcomes.

Ashwagandha (Withania somnifera) is an Ayurvedic adaptogen whose withanolides modulate the HPA axis, reduce nocturnal cortisol, and support circadian-aligned sleep. A PLOS ONE meta-analysis (2021) of RCTs found a standardized mean difference of -0.59 for sleep improvement versus placebo. It supports circadian balance by normalizing the cortisol-melatonin hormonal axis.

GABA is the primary inhibitory neurotransmitter and plays a central mechanistic role in sleep-wake cycle regulation. GABAergic neurons in the ventrolateral preoptic area drive sleep onset by inhibiting wake-promoting systems. A 2019 PMC study found GABA combined with L-theanine decreased sleep latency by 41.6% and improved NREM sleep architecture.

Glycine acts on NMDA receptors in the suprachiasmatic nucleus (SCN), the master circadian clock, inducing peripheral vasodilation that lowers core body temperature — a key circadian sleep-onset trigger. It also stimulates arginine vasopressin expression, an SCN output signal. A randomized crossover trial (n=19) found 3 g glycine significantly reduced sleep onset time.

Hops (Humulus lupulus) is recognized by the German Commission E for sleep disturbances. Its compounds modulate GABA-A receptors and interact with melatonin and serotonin receptors. A chrononutrition paper explicitly identifies hops alongside tryptophan as tools to improve sleep/wake circadian rhythms, and hops-valerian combinations show evidence of melatonin receptor interaction.

L-ornithine has been hypothesized and experimentally shown to influence circadian rhythms. Research shows it elevates striatal serotonin metabolite 5-HIAA, which drives nocturnal melatonin production and supports sleep-wake cycling. A randomized crossover trial (Chronobiol Int 2018) investigated L-ornithine's direct effect on the human circadian clock. Mouse studies in Scientific Reports (2016) confirmed that L-ornithine affects peripheral clock gene expression.

L-Theanine, a non-protein amino acid from green tea, improves sleep quality through GABAergic, serotonergic, and melatonin-elevating mechanisms. A 2022 PMC animal study showed Mg-L-Theanine increased melatonin levels, enhanced delta wave power, and reduced sleep latency. Authoritative nutritional reviews identify it among nutraceuticals with evidence for circadian rhythm and sleep disturbance support.

L-Tryptophan is the essential amino acid precursor to serotonin and melatonin, both central to circadian rhythm regulation. Chrononutrition research demonstrates tryptophan-enriched diets raise melatonin levels and improve sleep/wake circadian rhythm consolidation in elderly individuals. A peer-reviewed chrononutrition paper specifically classifies tryptophan as a tool to improve circadian rhythms.

Magnesium undergoes circadian oscillations of intracellular concentration in eukaryotic cells, and these rhythms are integral to cellular timekeeping. A 2016 Nature study demonstrated daily magnesium fluxes regulate cellular circadian timekeeping and energy balance. Magnesium deficiency disrupts clock gene expression (PER2) and sleep architecture.

Melatonin is the primary endogenous chronobiotic hormone produced by the pineal gland. Exogenous melatonin has strong RCT evidence for phase-shifting the circadian clock, treating delayed sleep phase syndrome, jet lag, and free-running circadian rhythm in blind individuals. A 2022 systematic review and meta-analysis confirmed phase-advancing effects and sleep consolidation across populations.

MeCbl has been studied in the context of circadian rhythm disorders, with human and animal data showing it can phase-advance the melatonin rhythm and enhance light-induced circadian phase shifts. Clinical use in delayed sleep phase disorder (DSPD) and non-24-hour sleep-wake syndrome has been investigated. Effects appear to involve facilitation of melatonin synthesis in the pineal gland.

Omega-3 polyunsaturated fatty acids (EPA and DHA) function as non-photic circadian zeitgebers, modulating molecular clock genes including BMAL1, CLOCK, PER, and CRY. A 2022 MDPI review covering 20 animal and human trials confirmed omega-3 FAs regulate circadian processes via clock gene pathways and are therapeutically beneficial for circadian disruption-related pathologies.

Passionflower extract (Passiflora incarnata) has been shown in a PMC study to induce high-amplitude rhythms in circadian clock gene expression (PER2, CRY1, BMAL1, CLOCK) both in vitro and in vivo without causing phase shifts — a circadian-stabilizing profile. It has traditional use in North American and European herbalism for sleep and anxiety.

Valerian root (Valeriana officinalis) has centuries of traditional European use as a sleep aid, recognized by the German Commission E for sleep disturbances. Valerenic acid modulates GABA-A receptors and partially agonizes 5-HT5A serotonin receptors highly expressed in the suprachiasmatic nucleus, the circadian pacemaker. A systematic review and meta-analysis (PMC 2020) confirmed sleep quality improvement.