Vitamin B12 status of Spanish vegetarians determined by cobalamin and methylmalonic acid serum levels

[Introduction]: Vitamin B12 deficiency is a common health issue in vegetarians, and especially in vegans, if fortified foods or supplements are not consumed. There is no ideal diagnostic marker of vitamin B12 deficiency, as the single determination of the total serum vitamin levels usually does not rule out functional deficiency conditions. Methylmalonic acid (MMA), an intermediate of the one carbon metabolism in which vitamin B12 participates as a cofactor, increases prior to the vitamin B12 decrease and is a good biomarker of the status of this vitamin. [Objectives]: In this study we present for the first time the vitamin B12 status of Spanish vegetarians, studied by both serum MMA and vitamin B12. In addition, we examine the influence of the dietary preferences (ovo-lacto vegetarian or vegan) and the intake of cobalamin supplements. [Methods]: Healthy vegetarian adults (n=104) were recruited. Dietary patterns and consumption of supplements were assessed by questionnaires and blood samples were collected. Serum vitamin B12 was measured by chemiluminiscence and serum MMA by liquid chromatography tandem mass spectrometry (LC-MS/MS). [Results]: Obtained median (IQR) values were: vitamin B12, 280.4 (160.2) pmol/l, MMA, 139.9 (78.9) nmol/l. There were no differences associated to gender, age or the type of vegetarian diet. The consideration of vitamin B12 levels alone resulted in the detection of 2 deficient individuals, while the addition of MMA as a second marker identified 10% of mild deficient subjects. Consumption of vitamin B12 supplements, by 75% of the participants, involved higher vitamin B12 (p<0.001) and lower MMA (p=0.012) levels compared to non-consumption. [Conclusions]: The studied Spanish lacto-ovo vegetarians and vegans presented a generally sufficient cobalamin status, which can be explained by the extended awareness of the need of supplement consumption.