In strict Jainism, turmeric is generally not considered allowed as food, because it comes from an underground rhizome/root-type part of the plant. Jain dietary principles avoid such foods due to ahimsa, since uprooting them is seen as harming many tiny living beings and the plant itself.

So the correct understanding is:

• Fresh turmeric root: not allowed in strict Jain diet.
• Turmeric powder: also usually avoided in strict Jain practice, because it is made from that root/rhizome.
• Why some people think it is allowed: in some households or regional practices, turmeric is used in a loose or customary way, but that is not the strict Jain rule.

The main Jain principle is to avoid:

• root vegetables
• foods that involve more harm in harvesting
• ingredients linked with greater violence to living beings

So, if someone says turmeric is allowed in Jainism, that is usually a practical custom, not the strict Jain scriptural ideal.