Thiamine Intake Needs

SLC19A2 and SLC19A3 code for the two transporters that move thiamine (vitamin B1) from the gut into the bloodstream and from blood into cells. Thiamine is the spark plug for converting carbohydrates into ATP. Without enough of it in tissues, the energy engine sputters regardless of how much fuel arrives.

Carriers of common SLC19A2/SLC19A3 reduced-activity variants are associated with lower tissue thiamine despite adequate dietary intake, and may experience fatigue, brain fog, or exercise intolerance that standard bloodwork misses (serum thiamine often stays in range while functional status is low). Carriers of higher-activity variants tend to maintain levels on default intake.

Alcohol blocks thiamine absorption and accelerates depletion. Heavy use is the classic driver of clinical deficiency. High-carbohydrate diets raise thiamine demand because every gram of carbohydrate metabolized consumes thiamine. Coffee, tea, and raw fish contain anti-thiamine compounds that further deplete stores. Magnesium status influences how well the body uses what’s absorbed.

Standard B-complex supplements usually cover the need for typical-function carriers. Carriers of the reduced-transport pattern may need benfotiamine (a fat-soluble form that bypasses the transporter) to actually move tissue levels, a meaningfully different intervention from "take more B1."