Folate and B ₁₂ status in women during British Army basic training: a prospective cohort study exploring implications for endurance performance and bone density and metabolism

This study investigated changes in serum folate and B₁₂, and associations with endurance performance and bone outcomes, in women during military training. Women (<i>n</i> 137) had serum folate and B₁₂, haematological markers and endurance performance (2·4 km run) measured at the start (week 1) and end (week 13) of British Army basic training. Whole-body areal bone mineral density and markers of bone metabolism were measured at week 1. Training decreased serum folate (mean change (95 % CI), -2·3 (-3·0, -1·6) nmol ∙ l^-1, <i>P</i> < 0·001), B₁₂ (-16 (-32, 0) pmol ∙ l^-1, <i>P</i> = 0·042), Hb (-0·7 (-0·9, -0·5) g ∙ dl^-1, <i>P</i> < 0·001) and erythrocyte count (-0·2 (-0·3, -0·2) × 10^9 ∙ l^-1, <i>P</i> < 0·001), but had no effect on mean corpuscular volume (<i>P</i> = 0·438) or erythrocyte distribution width (<i>P</i> = 0·088). There was no association between serum folate, serum B₁₂, Hb or erythrocyte count with run time (<i>P</i> ≥ 0·518). Serum B₁₂ was not associated with areal bone mineral density or bone metabolism at week 1 (<i>P</i> ≥ 0·152). Higher serum folate was associated with lower plasma c-telopeptide cross-links of type I collagen (standardised <i>β</i> (95 % CI) = -0·31 (-0·48, -0·15), <i>P</i> < 0·001), but not whole-body bone mineral density or plasma procollagen type I N-terminal propeptide (<i>P</i> ≥ 0·152). Serum folate and B₁₂ decreased after military training in women, resulting in a high prevalence of folate deficiencies at the end of training. Low serum folate may contribute to increased bone resorption, the implications of which are unclear.