Intense exercise increases oxygen consumption and mitochondrial respiration, leading to elevated production of reactive oxygen species (ROS). While moderate ROS levels play an essential role in cellular signaling and training adaptation, excessive accumulation may overwhelm antioxidant defenses and promote oxidative damage to lipids, proteins, and nucleic acids. The balance between ROS production and endogenous antioxidant systems is therefore critical during and after strenuous exercise. Traditional antioxidant supplementation has produced inconsistent findings, with some evidence suggesting that high doses of exogenous antioxidants may blunt adaptive signaling. Consequently, attention has shifted toward nutritional strategies that enhance endogenous cytoprotective pathways rather than directly scavenging free radicals.
Broccoli is rich in glucoraphanin, the precursor of sulforaphane (SFN), a bioactive isothiocyanate formed through myrosinase-mediated hydrolysis. SFN activates the Nrf2 signaling pathway, upregulating phase II detoxifying and antioxidant enzymes such as heme oxygenase-1 and NAD(P)H quinone oxidoreductase-1, thereby strengthening intrinsic antioxidant defense mechanisms. Although sulforaphane has demonstrated cytoprotective and anti-inflammatory properties, its effects on exercise-induced oxidative stress in healthy, recreationally active individuals remain insufficiently characterized. The present study examined whether short-term broccoli powder supplementation enriched with myrosinase influences sulforaphane bioavailability, oxidative stress, performance, and recovery following metabolically demanding exercise.
Seventeen healthy young men (23.8 ± 4.9 years) completed a randomized, double-blind, placebo-controlled crossover study with a three-week washout period. Ethical approval was obtained from the Lithuanian Sports University Ethics Committee, and all participants provided written informed consent. Participants maintained habitual diet and physical activity and reported intake of caffeine, alcohol, cruciferous vegetables, and supplements prior to testing.
The intervention consisted of 10 g broccoli powder (99.5% broccoli powder, 0.5% mustard seed powder providing myrosinase; \~320 μg glucoraphanin per dose) mixed with 300 mL beverage. The placebo consisted of spinach powder prepared identically. Ten doses were consumed over 14 days, with the final dose ingested three hours before exercise testing.
Sulforaphane bioavailability was assessed from 24-hour urine collection after the first dose using liquid chromatography-mass spectrometry. The exercise protocol involved an incremental cycling test to voluntary exhaustion starting at 40 W with a ramp increase of 20 W per minute. Respiratory gases and heart rate were continuously measured, and VO₂max was determined as the highest 20-second average achieved, verified by standard physiological criteria.
Countermovement jump height was assessed before exercise and 1, 30, and 60 minutes post-exercise. Capillary blood lactate was measured pre-exercise and during recovery (1-60 minutes). Venous blood samples were collected before and one hour after exercise to determine plasma malondialdehyde concentration as a marker of lipid peroxidation. Data were analyzed using repeated measures ANOVA with statistical significance set at p \< 0.05.
