When proteins are digested, they are broken down into smaller units called amino acids. Here's a breakdown:

* Proteins are long chains of amino acids linked together.

* Digestion involves breaking these chains apart.

* Amino acids are the individual building blocks of proteins.

So, the substances produced when proteins are digested are primarily amino acids.

In addition to amino acids, some other substances may be produced during protein digestion, such as:

* Dipeptides and tripeptides: These are short chains of two or three amino acids that are formed as the protein chains are broken down.

* Water: The breaking of peptide bonds between amino acids releases water molecules.

* Small amounts of other molecules: Depending on the specific protein, other molecules like vitamins, minerals, and hormones may also be released during digestion.

However, amino acids are the main product of protein digestion and are essential for building and repairing tissues, making enzymes and hormones, and many other functions in the body.