Abstract
Vitamins B6, B12 and folate play crucial metabolic roles especially during the reproductive years for women. There is limited reporting of within-subject variability of these vitamins. This study aimed to determine the within and between subject variability in serum vitamins B6, B12, folate and erythrocyte folate concentrations in young women; identify factors that contribute to variability; and determine dietary intakes and sources of these vitamins. Data were obtained from the control group of a trial aimed at investigating the effect of iron on the nutritional status of young women (age 25.2 ± 4.2 year; BMI 21.9 ± 2.2 kg/m2). The coefficients of variability within-subject (CVI) and between-subject (CVG) for serum vitamins B6, B12 and folate, and erythrocyte folate were calculated. Food frequency questionnaires provided dietary data. CVI and CVG were in the range 16.1%–25.7% and 31.7%–62.2%, respectively. Oral contraceptive pill (OCP) use was associated (P = 0.042) with lower serum vitamin B12 concentrations. Initial values were 172 ± 16 pmol/L and 318 ± 51 pmol/L for OCP and non-OCP users, respectively; with differences maintained at four time points over 12 weeks. BMI, age, physical activity, alcohol intake and haematological variables did not affect serum or erythrocyte vitamin concentrations. Vitamin B12 intakes were derived from traditional and unexpected sources including commercial energy drinks. Young women using OCP had significantly lower serum vitamin B12 concentrations. This should be considered in clinical decision making and requires further investigation.
Highlights
Vitamins B6, B12 and folate play crucial inter-related roles in DNA synthesis throughout the lifecycle especially during childhood, adolescence and the reproductive years for women [1,2,3].Studies have shown an inverse correlation between the intake of folic acid during pregnancy and infants born with neural tube defects [4,5]; a higher incidence of neurological disorders when vitamin B12 deficiency persists [6]; and anaemia, depression and confusion present with vitamin B6 deficiency [3].The concentrations of the vitamins in the circulation reflect an individual’s storage of these vitamins and their dietary intakes
There were no significant differences between Oral contraceptive pill (OCP) users or non-OCP users for Mean corpuscular volume (MCV) (89.1 ± 2.7 fL and 90.4 ± 3.5 fL)
The present study suggests that more than three samples are required to account for within-subject variability for serum vitamins B6, B12 and folate in women of reproductive age
Summary
Vitamins B6, B12 and folate play crucial inter-related roles in DNA synthesis throughout the lifecycle especially during childhood, adolescence and the reproductive years for women [1,2,3].Studies have shown an inverse correlation between the intake of folic acid during pregnancy and infants born with neural tube defects [4,5]; a higher incidence of neurological disorders when vitamin B12 deficiency persists [6]; and anaemia, depression and confusion present with vitamin B6 deficiency [3].The concentrations of the vitamins in the circulation reflect an individual’s storage of these vitamins and their dietary intakes. For vitamin B12, intakes are determined by the predominant animal sources available to a population and the preferences of individuals [7,8]. While investigating the effects of meat or iron supplementation on biomarkers of nutritional status, we identified a failure of this population to meet dietary recommendations for vitamins B6, B12 and folate [9]. As vitamin B6 is not limited to animal foods, there is some lessening of the impact of this trend. The vitamin B6 non-animal sources include processed cereals, fruits and vegetables [11]. Whether the predominant dietary sources of vitamins B6, B12 and folate for young women are reflective of the foods analysed as having a high content of these vitamins is uncertain
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