What is meant by the bioavailability of a vitamin? How is it determined?

Question

What will be an ideal response?

Answer 1

Some water-soluble vitamins are synthesized by GI tract bacteria and absorbed by the large intestine, but not in quantities great enough to meet the body's needs; foods must supply these essential nutrients. The amount of vitamins available from foods depends not only on the quantity provided by a food but also on the amount absorbed and used by the body—referred to as the vitamins' bioavailability. The quantity of vitamins in a food can be determined relatively easily. Researchers analyze foods to determine the vitamin contents and publish the results in tables of food composition. Determining the bioavailability of a vitamin is a more complex task because it depends on many factors, including:
Efficiency of digestion and time of transit through the GI tract
Previous nutrient intake and nutrition status
Method of food preparation (raw, cooked, or processed)
Source of the nutrient (synthetic, fortified, or naturally occurring)
Other foods consumed at the same time