Dietary Melatonin Intake Linked to Lower Rates of Obesity and Depression

Key Takeaways: 

• Higher intake of melatonin from foods was associated with lower prevalence of obesity and depression in a large cohort of Brazilian university graduates.
  
• No significant associations were found between dietary melatonin intake and most cardiometabolic outcomes, including hypertension, metabolic syndrome or type 2 diabetes.
  
• The strongest associations were observed at moderate rather than very high levels of dietary melatonin intake, highlighting the complexity of diet–health relationships.
  
  
  

Background and study context

In a study published in the Journal of Human Nutrition and Dietetics, researchers examined the melatonin content of commonly consumed foods and explored how dietary melatonin intake was associated with a range of health outcomes. The analysis used cross-sectional data from a large cohort of Brazilian university graduates.

Melatonin is a hormone best known for regulating circadian rhythms and sleep–wake cycles. Beyond its endogenous production, melatonin is also present in both animal-based and plant-based foods. Experimental, observational and supplementation studies have linked melatonin to sleep regulation, mood, and metabolic health. Although the concentration of melatonin in foods is considerably lower than in supplements, diets rich in melatonin-containing foods have been shown to increase circulating melatonin levels within physiological ranges.

Previous evidence suggests that increasing melatonin intake through food may deliver doses that align more closely with natural circadian rhythms than pharmacological supplementation, potentially avoiding suprapharmacological exposure. On this basis, dietary melatonin has attracted interest as a marker of broader dietary patterns rather than as a direct therapeutic intervention.

Rationale for examining dietary melatonin

Obesity, depression and sleep disorders represent a substantial and growing public health burden. Prior observational and experimental studies have suggested that melatonin may have protective effects against inflammatory, metabolic and neurobehavioural outcomes. In addition, observational research has reported inverse associations between melatonin exposure and outcomes such as liver cancer incidence and all-cause mortality.

Despite this, relatively few studies have investigated habitual dietary melatonin intake or its associations with chronic conditions in adult populations. The present study aimed to address this gap by estimating melatonin intake from the diet and examining its relationship with multiple health outcomes in a large cohort.

Study design and population

The analysis drew on data from the Cohort of Universities of Minas Gerais (CUME+) study. CUME+ is an open, prospective cohort designed to assess the impact of dietary patterns and nutrition transition on noncommunicable diseases.

At baseline, participants completed a questionnaire administered in two parts. The first part collected information on sociodemographic characteristics, clinical history, lifestyle factors, anthropometric measures and self-reported morbidity.

Dietary assessment and estimation of melatonin intake

The second part of the baseline assessment included a food frequency questionnaire (FFQ), alongside questions on dietary habits, supplement use and cooking practices. Nutrient intake was estimated using established food composition tables.

Dietary melatonin content was estimated based on values reported in the scientific literature for individual food items. These estimates were then adjusted for total energy intake to account for differences in overall food consumption between participants.

Health outcomes and definitions

The health outcomes assessed in the study included obesity, obstructive sleep apnoea (OSA), hypertension, metabolic syndrome (MetS), type 2 diabetes (T2D), sleep duration, dyslipidaemia and depression.

Obesity was defined as a body mass index of 30 kg/m² or higher. Depression and OSA were identified based on self-reported medical diagnoses.

Dyslipidaemia was defined as the presence of at least one abnormal lipid parameter, including total cholesterol of 200 mg/dL or higher, triglycerides of 150 mg/dL or higher, high-density lipoprotein cholesterol below 40 mg/dL for males or below 50 mg/dL for females, or low-density lipoprotein cholesterol of 130 mg/dL or higher.

Cardiometabolic criteria

Metabolic syndrome was defined as central obesity plus any two of the following criteria: elevated triglycerides or treatment for hypertriglyceridaemia, reduced high-density lipoprotein cholesterol or treatment, elevated blood pressure or treatment for hypertension, and elevated fasting plasma glucose or a diagnosis of type 2 diabetes.

Hypertension was defined by the use of antihypertensive medication, a physician diagnosis, systolic blood pressure of 140 mmHg or higher, or diastolic blood pressure of 90 mmHg or higher. Type 2 diabetes was defined as a self-reported or physician diagnosis, use of antidiabetic medication, or fasting plasma glucose of 126 mg/dL or higher.

Sleep duration was categorised as short if participants reported sleeping less than seven hours per day, and normal if they reported seven hours or more per day.

Statistical analysis

Associations between dietary melatonin intake and health outcomes were estimated using logistic and Poisson regression models. Analyses were adjusted for a wide range of potential confounders, including age, sex, family income, binge drinking, smoking status, screen time, physical activity, medication use and sleep duration.

Participant characteristics

The final analysis included 8,320 participants with a mean age of 35.9 years. Most participants were female and reported that they did not smoke. Around one third of the cohort reported short sleep duration.

Dyslipidaemia, depression, obesity and hypertension were the most commonly reported health conditions within the study population.

Melatonin content of foods and dietary sources

Melatonin content was estimated for 119 of the 144 food items included in the FFQ. Reported concentrations ranged from 0 to 169.9 ng per gram of food. Mean daily melatonin intake was estimated at 25,554.7 ng and was significantly higher in males than in females.

The main dietary sources of melatonin in this population were coffee, lentils and beans, and rice. Higher melatonin intake was associated with lower intake of protein, cholesterol, and saturated and monounsaturated fats, alongside higher intake of fibre and carbohydrates. These patterns suggest that dietary melatonin intake may reflect broader differences in dietary composition.

Associations with health outcomes

After full adjustment, no significant associations were observed between dietary melatonin intake and obstructive sleep apnoea, hypertension, metabolic syndrome or type 2 diabetes. Initial associations with sleep duration and dyslipidaemia were attenuated after adjustment for age and sex and did not remain statistically significant.

In contrast, dietary melatonin intake showed an inverse association with both obesity and depression. Participants with daily melatonin intakes between approximately 14,900 and 34,400 ng were less likely to have obesity, while intakes between approximately 14,900 and 25,000 ng were associated with a lower likelihood of depression.

Notably, the strongest associations were observed in intermediate intake quintiles rather than among those with the highest melatonin intake, suggesting a non-linear relationship.

Conclusions and implications

In this cohort of Brazilian university graduates, higher dietary melatonin intake was associated with lower prevalence of obesity and depression, while no significant associations were identified for most other cardiometabolic outcomes or sleep duration.

The findings support existing hypotheses that dietary melatonin may play a role in metabolic and neurobehavioural regulation, potentially through anti-inflammatory pathways. However, the cross-sectional design of the study means that causal relationships cannot be established.

Further longitudinal and experimental research is needed to confirm these associations, determine whether dietary melatonin has an independent effect beyond overall dietary patterns, and clarify the biological mechanisms that may underlie the observed relationships.

CCH insights:

This is an interesting study, but it is difficult to see where this research leads to. If a person is suspected of having obesity, depression or some other condition due to a lack of melatonin, the solution is surely likely to be supplementation of melatonin, not an increase in melatonin-rich foods – because dietary changes are notoriously difficult to adhere to and when we are looking at just one nutrient, supplementation is a much easier option.