In Jain dharma, bread made with yeast is generally avoided, or taken only by less‑strict Jains, because:

1. Yeast is living

- Yeast is a one‑sensed living organism (like a tiny fungus). - When we use yeast to rise dough, we are cultivating and then killing countless small living beings in the process of fermentation and baking. - This goes against ahimsā (non‑violence), the main principle of Jainism. ( jainknowledge.com)

1. Fermentation multiplies life

- In fermentation, millions of micro‑organisms (like nigod/yeast) grow and multiply in the dough. - Eating or baking that dough means harming many more lives than a simple, non‑fermented roti or chapati. ( jainknowledge.com)

1. Traditional Jain rules

- Both Śvetāmbara and Digambar traditions teach to avoid fermented foods like: - Yeast bread - Idli/dosa batter - Vinegar, alcohol, etc. - Especially during Paryushan / Das‑lakshan, bread and other yeast items are clearly not taken. ( jainknowledge.com)

1. Safer Jain option

- Instead of yeast bread, Jains prefer: - Fresh roti / chapati / phulka - Khakhra - Other simple unleavened (without yeast) breads made same day. ( jainknowledge.com)

So, “bread with yeast” is called non‑Jain or not suitable for strict Jains, because it involves intentional himsā to countless microscopic living beings through fermentation and baking.

You can read more here