Sweet relief: a randomised controlled trial of the effectiveness of dark chocolate for managing menstrual cycle-related symptoms in female athletes

Abstract Background Female athletes frequently report menstrual cycle-related symptoms (MCS), which impact wellbeing, training and perceived performance, prompting exploration of strategies to support symptom management. Dark chocolate is rich in cocoa polyphenols and other bioactive compounds that may influence inflammatory, oxidative stress, mood- and pain-related pathways implicated in MCS. This study evaluated dark chocolate as a strategy to manage MCS in female athletes. Twenty-five athletes consumed 40 g of 70% dark ( n = 13) or 25% milk ( n = 12) chocolate daily for eight days (-4 to + 4 days from bleeding onset) across two menstrual or hormonal contraceptive cycles, following a two-cycle baseline. Primary outcomes were MCS frequency and severity, brain fog, and high sensitivity C-reactive protein. Exit interviews captured expectations and perceptions. Results Over 70% of participants reported moderate baseline MCS severity. Among nine MCS clusters, the dark chocolate group showed the largest, albeit non-significant, declines in negative affect (Δ = –1.21, p = 0.06) and pain (Δ = –0.65, p = 0.07); changes in the milk chocolate group were small (|Δ|≤ 0.64). Linear mixed models revealed no significant effects of time, group, or interaction ( p > 0.97) on primary outcomes. Interviews indicated (1) mixed expectations, (2) perceived but hard-to-isolate symptom relief, (3) enjoyment/adherence, and (4) benefits from symptom tracking and communication. Conclusions Eight days of chocolate produced no group-level effects, yet the intervention was feasible and associated with individual perceptions of comfort and modest relief. Larger trials with higher doses and longer exposure are warranted. Trial registration ANZCTR.org.au. Trial registration ID: ACTRN12624000029594. Date of registration: 15/01/2024.