Jain people avoid onion and garlic mainly because they are root vegetables and are believed to involve greater harm to living beings and stronger passions.

Here is the Jain reasoning:

1. More violence in harvesting

- When a root is pulled out, the whole plant is destroyed. - In Jain dharma, ahimsa is central, so foods that cause more harm are avoided.

1. Many living beings are disturbed

- Root vegetables grow in the earth, where many subtle organisms are believed to exist. - Digging them out disturbs more life than picking fruits, leaves, or grains.

1. They are considered tamasic/ stimulating

- Onion and garlic are said to increase heat, smell, and stimulation in the body and mind. - Jain practice values control, purity, and calmness for spiritual discipline.

1. They are not suitable for spiritual restraint

- Jain food rules support simplicity, non-attachment, and purity. - So foods like onion and garlic are avoided as part of disciplined living.

In short: Jains avoid onion and garlic because they are root foods associated with greater violence and with effects that are considered unfavorable for spiritual purity and self-control.

If you want, I can also explain this from the perspective of Digambar and Shwetambar traditions.