Our bodies need enzymes to help digest the food we eat, this way we can absorb the nutrients and not cause any stress to our digestion system.
So there are 2 kinds of enzymes, one that is present in our food, the problem is because our food is mostly cooked or processed they lose their enzymes, and that stresses our digestion system, hence our immune system. A way to add in those lost enzymes is to get a good source of over-the-counter enzyme supplements and take them with your meals.
Another source of enzymes is produced in our stomach, however, as we age, we produce fewer enzymes. We can help our body produce more enzymes if we sip on a cup of hot water (or an herbal tea) while we eat, the hot water triggers our body to produce those enzymes, or drink a small glass of celery juice before our meal.
Don't forget to heat that kettle before you eat your snack!