Whey protein powder is a collection of proteins that are found in the watery part of milk. When cheese is produced, milk separates into two parts - a solid, fatty part (curds) that is cured to make cheese, and a watery part (whey) that is dried to make whey protein powder. This is very high in protein and is used in nutritional supplements such as protein shakes, meal replacements and protein bars.
Whey protein powder contains approximately 80% protein, which compares extremely well to other sources of protein such as meat, fish or eggs which at best contain only 31% protein. For more information on the protein content of different foods, please see our section on how to meet your daily protein requirements.