Strong spices help preserve the food and preservation is the opposite of digestion.
The spices used in every day cooked meal in mild doses are fenugreek, ginger paste, green chili paste, cumin seeds, coriander seeds and pepper powder.
It is better to use green chili after removing the seeds and in paste form. Ginger is also best used in paste form. Black petpper is best used in This is so they cause minimum irritation to intestinal walls.
Other spices like clove and cinnamon are best used once a week at the most.