When your digestive system is working well, the average transit time for food, from mouth to bowel movement, is anywhere from 12 to 24 hours.

Many people have a transit time that is too long, 48 to 96 hours, because they don’t eat enough high fiber food, drink enough water, or get enough exercise.

But how do you really know how long your transit time is? Here’s a way to find out:

• Swallow 1 gram of activated charcoal tablets (from your drugstore) or eat a couple of small beets, noting the exact time you do this.
• When you see darkened stool (charcoal will turn it black; beets will turn it deep red), figure out how many hours have passed. That is your transit time.
• If your transit time is more than 24 hours, eat more fruits, vegetables, whole grains and beans, and drink at least eight glasses of water a day.
• If your transit time is less than 12 hours, it could mean you’re not absorbing enough nutrients. Talk with your doctor about this.

Most people get less than 15 grams of fiber a day. The recommended amount of fiber for adults is at least 25 to 35 grams per day. The amount of fiber a child needs is based on their age: 10 grams plus the child’s age. An example… a child who is 8 years old would need 10 grams + 8 years = 18 grams per day.