OBJECTIVE: Arab populations lack data related to nutritional assessment in children with
autism spectrum disorders (ASDs), especially micronutrient deficiencies such as folate and
vitamin B12. METHODS: To assess the dietary and serum folate and vitamin B12 statuses, a
hospital-based case–control study was conducted in 80 Omani children (40 children with
ASDs versus 40 controls). RESULTS: The ASD cases showed significantly lower levels of
folate, vitamin B12, and related parameters in dietary intake and serum levels …

Folate measurements in serum may not reflect cytoplasmic methionine synthase activity,
exactly. Because there are many folate carrier systems at the cell membrane such as
reduced folate carriers and folate receptors that affect intracellular folate concentrations by
transporting folate molecules into the cell [2, 3], measurements of red blood cell (RBC) folate
concentrations may help to interpret the methionine synthase activity, correctly.