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Objective. To evaluate whether supplementation with an L-methionine combination would reduce the incidence of upper respiratory tract symptoms (URTS) and improve performance in ultramarathon runners. Design.A double-blind placebo-controlled study.Setting. Twenty-one ultramarathon runners (17 males, 4 females) preparing for participation in an 87.3 km ultramarathon.Interventions. L-methionine combination supplement (Lmethionine, vitamin B 6 , vitamin B 12 , folic acid and magnesium) or placebo containing potato starch. Main outcome measures.Incidence of URTS was recorded during the runner's preparation for an ultramarathon race (75 days) and recovery from the same (75 days). CD4+, CD8+ cell counts and ratios were measured pre race, immediately post race and 75 days post race. VO 2max and endurance fitness (percentage VO 2max at 4 mmol -1 lactate concentration) were measured during the preparation period for the race.Results. During the preparation period the incidence of URTS was 36% in the supplement group and 80% in the placebo group (p = 0.08). The incidence of URTS during the 3 weeks post race was 27% in the supplement group and 40% in the placebo group (p = 0.65). The CD4+/CD8+ cell ratios were not significantly different between groups. Endurance fitness prior to the race and race times were not significantly different. Conclusions.Although the findings of the current study show that an L-methionine combination supplement did not reduce the incidence of URTS or improve performance in ultramarathon runners, benefits may be found with a more detailed investigation using larger sample sizes and immunosuppressed athletes.

Objective. To evaluate whether supplementation with an L-methionine combination would reduce the incidence of upper respiratory tract symptoms (URTS) and improve performance in ultramarathon runners. Design.A double-blind placebo-controlled study.Setting. Twenty-one ultramarathon runners (17 males, 4 females) preparing for participation in an 87.3 km ultramarathon.Interventions. L-methionine combination supplement (Lmethionine, vitamin B 6 , vitamin B 12 , folic acid and magnesium) or placebo containing potato starch. Main outcome measures.Incidence of URTS was recorded during the runner's preparation for an ultramarathon race (75 days) and recovery from the same (75 days). CD4+, CD8+ cell counts and ratios were measured pre race, immediately post race and 75 days post race. VO 2max and endurance fitness (percentage VO 2max at 4 mmol -1 lactate concentration) were measured during the preparation period for the race.Results. During the preparation period the incidence of URTS was 36% in the supplement group and 80% in the placebo group (p = 0.08). The incidence of URTS during the 3 weeks post race was 27% in the supplement group and 40% in the placebo group (p = 0.65). The CD4+/CD8+ cell ratios were not significantly different between groups. Endurance fitness prior to the race and race times were not significantly different. Conclusions.Although the findings of the current study show that an L-methionine combination supplement did not reduce the incidence of URTS or improve performance in ultramarathon runners, benefits may be found with a more detailed investigation using larger sample sizes and immunosuppressed athletes.