Nutritional supplements comprising keratin protein either in powder or liquid form as well as novel methods of producing soluble keratin proteins by oxidation are provided. In one embodiment of the disclosure, a soluble keratin protein product can be produced by treating an insoluble keratin source in an oxidizing solution at low pH and heat for a sufficient time to oxidize essentially all of the cysteine residues in the protein. By then raising the pH to the pKa of the proteins, or to the point at which the protein is present in the salt form, a solution of high molecular weight proteins that are in a low salt solution can be obtained. This solution is essentially free of peptides and salts that have an adverse effect on flavor and palatability, and maintains a high proportion of sulfur amino acids for beneficial health effects. The resulting protein product can be dissolved into water, juice, or a nutritional drink, or sprinkled on food. Alternatively, the protein can be provided as a liquid supplement.
