AIM: The purpose of the current study was to examine the effect of Astaxanthin 
(Asx) supplementation on muscle enzymes as indirect markers of muscle damage, 
oxidative stress markers and antioxidant response in elite young soccer players.
METHODS: Thirty-two male elite soccer players were randomly assigned in a 
double-blind fashion to Asx and placebo (P) group. After the 90 days of 
supplementation, the athletes performed a 2 hour acute exercise bout. Blood 
samples were obtained before and after 90 days of supplementation and after the 
exercise at the end of observational period for analysis of thiobarbituric 
acid-reacting substances (TBARS), advanced oxidation protein products (AOPP), 
superoxide anion (O2•¯), total antioxidative status (TAS), sulphydril groups 
(SH), superoxide-dismutase (SOD), serum creatine kinase (CK) and aspartate 
aminotransferase (AST).
RESULTS: TBARS and AOPP levels did not change throughout the study. Regular 
training significantly increased O2•¯ levels (main training effect, P<0.01). 
O2•¯ concentrations increased after the soccer exercise (main exercise effect, 
P<0.01), but these changes reached statistical significance only in the P group 
(exercise x supplementation effect, P<0.05). TAS levels decreased significantly 
post- exercise only in P group (P<0.01). Both Asx and P groups experienced 
increase in total SH groups content (by 21% and 9%, respectively) and 
supplementation effect was marginally significant (P=0.08). Basal SOD activity 
significantly decreased both in P and in Asx group by the end of the study (main 
training effect, P<0.01). All participants showed a significant decrease in 
basal CK and AST activities after 90 days (main training effect, P<0.01 and 
P<0.001, respectively). CK and AST activities in serum significantly increased 
as result of soccer exercise (main exercise effect, P<0.001 and P<0.01, 
respectively). Postexercise CK and AST levels were significantly lower in Asx 
group compared to P group (P<0.05)
CONCLUSION: The results of the present study suggest that soccer training and 
soccer exercise are associated with excessive production of free radicals and 
oxidative stress, which might diminish antioxidant system efficiency. 
Supplementation with Asx could prevent exercise induced free radical production 
and depletion of non-enzymatic antioxidant defense in young soccer players.