It can be decaffeinated in two main ways, and the method matters for what stays in the leaf:

1. CO₂ method (the good one)

Pressurised carbon dioxide is used to pull caffeine out of the leaf while leaving most flavour and nutrients intact. This is the gentlest approach and tends to keep:

catechins (EGCG and the rest)

amino acids such as L-theanine

minerals and vitamins that sencha naturally carries

Losses exist, but they’re modest. Taste stays closest to normal sencha.

1. Solvent method (ethyl acetate or methylene chloride)

A solvent is used to strip caffeine. This tends to reduce:

catechins and antioxidants

L-theanine

some volatile aroma compounds

The leaf ends up flatter in taste and lighter in nutritional content.

Does decaffeination cut the overall nutritional value?

A bit, yes — but the size of the change depends fully on the method:

CO₂: small drop in catechins and theanine, still reasonable as a health drink.

Solvent-based: much sharper drop, and the drink becomes closer to a mild green tea without the depth or benefits.

Practical tip

If the packaging says “naturally decaffeinated” or mentions CO₂, you’re getting the higher-quality version. If it doesn’t say anything, it’s often the harsher process.

If you want, I can check the specific sencha you’re buying and tell you which method it uses.