Journal Title (Medline/Pubmed accepted abbreviation): Int J Sport Nutr Exerc Metab
Page numbers: 195-204
doi (if applicable):
Summary of Background and Research Design
Hypothesis:The authors did not state a specific hypothesis. However, they reviewed the role of thiamin and riboflavin in energy metabolism and how important this is to athletes. In addition, they cited some cases studies of athletes with low B-vitamin status, especially thiamin. Therefore, the authors wanted to examine thiamin and riboflavin in a population of swimmers during periods of differing training intensity and energy expenditure.
Subjects:: 19 members of a university swim team (6 men, 13 women; mean age 19.5 y). Subjects underwent swim training 16 h/week and dry land training for 10 h/week throughout the year (1 month off-season in September).
Experimental design:: Observational, cross-sectional
Treatments: No treatments assigned.
Protocol: The study consisted of two observational periods: a 9-day preparation period during October and a 7-day during the November-February intensive training phase. During each of these periods, anthropometric measures were taken (height, weight, % body fat), blood samples were collected, resting energy expenditure was measured via indirect calorimetry and total energy requirement was estimated (via use of 3-day activity records), and 3-day food records were obtained.
Summary of research findings:
- The male swimmers averaged ~10% body fat and the female swimmers were ~23% body fat.
- Estimated total daily energy requirement increased by about 300 kcals per day in men and by nearly 500 kcal/day for men when comparing the preparation period vs. the intensive training period.
- Thiamin and riboflavin intakes were not significantly different between the preparation period and intensive training period for men or women. Mean thiamin intakes were 1.42-1.44 mg/day for men and 1.28-1.51 mg/day for women, which were both slightly above the Recommended Dietary Allowance (RDA) for thiamin (1.2 mg for men and 1.1 mg for women. Similarly, mean riboflavin intakes for both men and women were above RDA.
- Blood thiamin levels were significantly lower in the intensive training vs. preparation period for both men (36?3 vs. 41?10 ng/mL, P=0.048) and women (31?5 vs. 38?10 ng/mL, P=0.004). The authors listed a suggested normal clinical range for thiamin of 26-56 ng/mL. Thus, on a mean basis, the lower levels of blood thiamin were still in the normal clinical range. The authors did report that 2 female athletes had blood thiamin levels slightly below the normal clinical range, but there was no evidence of thiamin deficiency associated with these values.
- There were no significant changes in blood riboflavin levels between the two training periods for either males or females.
Interpretation of findings/Key practice applications:
It appears that thiamin status was more likely to be affected by intensive swimming training than is riboflavin status in this population. Given that dietary intakes of thiamin did not differ, it is likely that increased training may have elevated the thiamin need somewhat. It is important to note, however, that estimation of nutrient intakes via food records can be difficult. Subjects often underreport food intake. This may mean that thiamin intakes were underestimated in this study and it is unknown if any underreporting that might have existed would have been consistent between the intensive-training and preparation periods.