The concept of "bioavailability" might be too simple when talking about nutrition. Heme iron from animal products and vitamin A from liver are bioavailable to t

The concept of "bioavailability" might be too simple when talking about nutrition. Heme iron from animal products and vitamin A from liver are bioavailable to the point of being toxic. With the example of iron, our body has variable absorption rate based on how much we need; heme iron bypasses this mechanism and gives us extra iron.