The aim of the present 3-month randomized, placebo-controlled trial was to evaluate whether adherence to Mediterranean Diet (MD) together with melatonin oral treatment or plaebo, would ameliorate Cancer Related Fatigue in Breast Cancer patients receiving chemotherapy treatment.

Cancer related fatigue (CRF) is a common distressing complaint in breast cancer (BC) patients treated with chemotherapy. Nutrition quality plays a pivotal role in CRF, while an increased interest towards new pharmacological agents has been observed.

Melatonin, an endogenous hormone that regulates the human sleep-wake cycle, could alleviate CRF.

In the present randomized, placebo-controlled 3-month trial, we investigated the effects of melatonin intake (i.e., 1 mg/day) vs. placebo on CRF of BC patients. Melatonin and placebo tablets were of similar physical and sensory properties. In both arms, Mediterranean diet (MD) was implemented. Medical history, anthropometry and blood withdrawal were performed. CRF was evaluated by the Functional Assessment of Chronic Illness Therapy - Fatigue questionnaire and MD adherence by the MedDiet Score.

Inclusion criteria:

1. adult women (≥ 18 years of age) with BC diagnosis who underwent chemotherapy at the time of invitation,

2. women receiving pharmacological treatment that did not interact with melatonin,

3. women receiving standard pharmacological treatment for at least last two months prior to study initiation,

4. patients with good performance status, as indicated by scoring "0 or 1" of the Eastern Cooperative Oncology Performance Status (ECOG PS) questionnaire [26],

5. patients not needing a transfusion, as indicated by hemoglobin ≥ 9 g/dL,

6. patients having the ability to understand and give a written statement of consent.

   Patients were excluded from the study when:

7. fatigue was attributed to conditions other than cancer e.g., uncontrolled hypothyroidism, hypercalcemia, congestive heart failure, chronic obstructive pulmonary disease,

8. using pharmacological agents for CRF or sleeping disorders prior to the study,

9. pharmacological treatment that was modified during the study or that could interact with melatonin,

10. diagnosed with gastrointestinal diseases that could affect absorption of nutrients such as inflammatory bowel diseases infections.

11. diagnosed with psychiatric disorders such as depression, psychosis, bipolar disorder, and receiving equivalent medication.

12. excessive alcohol consumption.

13. a lifestyle that can affect sleep patterns (e.g., night shifts).

14. patients with a poor clinical state as indicated by laboratory markers: creatinine clearance < 30 mL/min; aspartate aminotransferase (AST) > 3 x upper limit of normal (ULN); alanine aminotransferase (ALT) > 3 x ULN; bilirubin > 1 x ULN.