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Melatonin and serotonin rhythms, which exhibit a close association with the endogenous circadian component of sleep, are attenuated with increasing age. This decrease seems to be linked to sleep alterations in the elderly. Chrononutrition is a field of chronobiology that establishes the principle of consuming foodstuffs at times of the day when they are more useful for health, improving, therefore, biorhythms and physical performance. Our aim was to analyze whether the consumption of cereals enriched with tryptophan, the precursor of both serotonin and melatonin, may help in the reconsolidation of the sleep/wake cycle and counteract depression and anxiety in 35 middle-aged/elderly (aged 55-75 year) volunteers in a simple blind assay. Data were collected for 3 weeks according to the following schedule: The control week participants consumed standard cereals (22.5 mg tryptophan in 30 g cereals per dose) at breakfast and dinner; for the treatment week, cereals enriched with a higher dose of tryptophan (60 mg tryptophan in 30 g cereals per dose) were eaten at both breakfast and dinner; the posttreatment week volunteers consumed their usual diet. Each participant wore a wrist actimeter that logged activity during the whole experiment. Urine was collected to analyze melatonin and serotonin urinary metabolites and to measure total antioxidant capacity. The consumption of cereals containing the higher dose in tryptophan increased sleep efficiency, actual sleep time, immobile time, and decreased total nocturnal activity, sleep fragmentation index, and sleep latency. Urinary 6-sulfatoxymelatonin, 5-hydroxyindoleacetic acid levels, and urinary total antioxidant capacity also increased respectively after tryptophan-enriched cereal ingestion as well as improving anxiety and depression symptoms. Cereals enriched with tryptophan may be useful as a chrononutrition tool for alterations in the sleep/wake cycle due to age.

Aging is associated with an increased production of free radicals and alterations in the mechanisms of adaptation to stress. A number of studies have shown a causal connection between age-related oxidant/antioxidant imbalance and the diminution of an organism's melatonin levels in old age. Restoration of this rhythm may contribute to the re-stabilization of cellular homeostasis. The present work was aimed at examining the effect of the administration of melatonin or its precursor, the amino acid tryptophan, on heterophil lipid peroxidation (LPO) levels and superoxide dismutase (SOD) activity in heterophils from young (4-5 year) and old (12-14 year) ringdoves (Streptopelia risoria) under both basal and antigen-induced (stressful) conditions. Young animals were treated for 3 consecutive days with a single daily oral dose (0.25 mg) of melatonin at 1900 hours while old animals were treated for 3 consecutive days with either an oral dose (2.5 mg) of melatonin at 1900 hours or an oral capsule of 300 mg/kg body weight of L-tryptophan at 0900 hours. Non-treated old animals presented lower circulating levels of melatonin at night and higher levels of malonaldehyde (MDA) both day and night when compared to young birds. In both age groups, LPO levels were lower at night than during the day. Melatonin or tryptophan treatments significantly increased serum melatonin levels, reinforced SOD activity, and reduced MDA levels induced by the antigen. Melatonin and tryptophan may be useful agents for the treatment of disease states and processes in which an excessive production of oxidative damage occurs.