Digestive system ↗Vitamin A
Retinoids and carotenoids enter intestinal lipid handling, then chylomicrons; conversion and absorption vary.
DIGESTIVE / VITAMINS · MINERALS
Intake is only
the first gate.
Nutrient status reflects food content, release from the food matrix, chemical form, luminal conditions, transport, body demand, storage and loss. Different nutrients use different intestinal sites and vehicles.
12 REPRESENTATIVE ROUTES
Site matters.
Context matters.
This is a transport map, not a supplement recommendation. Requirements and upper limits vary by nutrient, age, sex, pregnancy, health state and jurisdiction.
Vitamin D
Dietary vitamin D uses micellar and chylomicron routes; skin synthesis and liver/kidney activation are separate steps.
Vitamin E
Absorption depends on fat digestion; hepatic lipoprotein handling helps determine circulating forms.
Vitamin K
Dietary forms use lipid absorption; vitamin-K antagonist medicines create a clinically important interaction context.
Folate
Food folates are processed before transporter-mediated small-intestinal absorption; supplemental folic acid differs in form.
Vitamin B12
Release from food, intrinsic factor, pancreatic function and terminal-ileal receptors form a multi-organ route.
Vitamin C
Saturable sodium-dependent intestinal transport supports absorption; excess is not absorbed without limit.
Thiamin and peers
B vitamins use nutrient-specific transporters and may have limited stores, but mechanisms and deficiency timelines differ.
Iron
Duodenal uptake depends on chemical form; hepcidin integrates stores, erythropoietic demand and inflammation.
Calcium
Vitamin D-regulated active and passive pathways contribute, with fractional absorption changing by dose and demand.
Magnesium
Passive and active intestinal uptake combine; kidneys are central to longer-term balance.
Zinc
Transport responds to intake and status, while phytate and other dietary components can affect bioavailability.