21.3: Conclusions (22a.3)

Folate is required for one-carbon meta­bolism and thus plays a critical role in essential biolog­ical processes, including amino acid meta­bolism, DNA synthesis and repair and methy­lation reactions. Low folate status leads to adverse health effects throughout the lifecycle, even if not severe enough to cause mega­loblastic anemia, the clinical manifestation of folate defi­ciency. Thus, accurate assess­ment of folate status is essential. Serum and RBC folate concen­trations are sensitive bio­markers used widely to assess folate status. Serum folate is the earliest indicator of altered folate exposure and reflects recent dietary intake, whilst RBC folate reflects tissue folate stores and is a better indicator of folate intake over the previous 3–4 months when circulating folate is incorporated into the maturating red cells. On the basis that normal homo­cys­teine meta­bolism requires an adequate supply of folate, the measure­ment of plasma homo­cys­teine provides a sensitive functional indicator that will be elevated with deficient or low folate status, but it is not a specific folate bio­marker as it is influenced by other nutrient (most notably vitamin B₁₂ defi­ciency) and non-nutrient factors including renal function. Emerging genomic bio­markers may provide a reliable assess­ment of genome pathology resulting from deficient status to folate, to add to the core bio­markers of status, serum folate, RBC folate, and plasma homo­cys­teine.