The organ that secretes enzymes which can digest all 3 energy-containing nutrients (carbohydrates, fats, and proteins) is the pancreas.

Here's why:

* Carbohydrates: The pancreas secretes amylase, which breaks down starch into simpler sugars.

* Fats: The pancreas releases lipase, which breaks down fats into fatty acids and glycerol.

* Proteins: The pancreas produces proteases (such as trypsin and chymotrypsin) which break down proteins into amino acids.

While other organs like the stomach and small intestine also play roles in digestion, the pancreas is unique in its ability to produce enzymes that can break down all three macronutrients.