What does brewer's yeast in this shampoo actually do for the hair? — MODUM KLASSIKA Beer Yeast Shampoo, 550 ml

Brewer's yeast is the reason this shampoo does more than simply remove dirt and excess oil. It contributes B-group vitamins, amino acids and yeast enzymes to a rinse-off product, and each of these has a different role in how the hair looks and feels after washing.

• B vitamins are closely linked to the condition of the hair shaft. In a shampoo, they help hair appear stronger and less straw-like, which matters when hair has become rough from frequent washing or heat styling.
• Amino acids are the building blocks of the protein hair is made from. In a cosmetic formula they are valued for making the lengths feel more supple and manageable, rather than for rebuilding the hair structure.
• Yeast enzymes give a conditioning effect to rough or damaged parts of the hair. Smoother strands reflect light more evenly, so hair can look shinier and colour can look richer and less faded.

Because the formula works while cleansing, it does not rely on heavy coating to create its effect. It is designed to clean the scalp and lengths and at the same time improve the look and feel of the hair shaft. That makes it a shampoo to return to when hair seems flat, tired or rough, not a substitute for a conditioner or mask on very dry ends.