Starting the tablet is not the same as being covered
Pooling 108 studies, the marker tied to neural tube defect risk took a median 36 weeks, with a range of 27 to 52, to settle at its new plateau on steady folic acid intake.
What the study found
Red cell folate takes a median 36 weeks to reach its new level
Starting the tablet is not the same as being covered. Pooling 108 studies, the marker tied to neural tube defect risk took a median 36 weeks, with a range of 27 to 52, to settle at its new plateau on steady folic acid intake, rising about 1.78-fold at fortification-level doses.
The caveat · A plateau, not a protective level
A plateau is not a threshold. This models how long a level takes to stop rising, not how long until enough folate is present to protect an embryo, and those are different points. The 906 nmol/L target it is anchored to comes from observational Chinese data rather than a trial. Most of the pooled studies were in adults who were not pregnant, and red cell folate assays are notoriously hard to compare between laboratories.