How do we know how much food nutrients are actually absorbed by the human body?

Question

I know there are chemical processes to detect the quantity of nutrients in food but how do we know how much of these nutrients are actually absorbed by the human body? How much variance is there between different people?

In: 27

Answer 1

Many nutrients are actively transported through the intestinal wall (the lumen) because as molecules they’re too large to readily diffuse. As a result, absorption of these nutrients is subject to regulation by the body.

Small molecules like sugars diffuse, so the blood concentration of them after you eat will depend on their concentration in the food mass.