With food if you must, but there is NO SUBSTITUTE for natural fiber from food. Veggies and Hemp Protein Powder drink mix are good, especially the latter, it's the closest to perfect food I ever investigated/ate!
Read the label. Most I think say thirty minutes before eating with a glass of water.
Eat natural food with fiber only because that is the right thing to do.
NEVER, unless prescibed by a competent doctor - instead eat lots of highfibre foods, low fat, non-prepackaged. IMPORTANT whether you do opt for fibre subsitutes or for real food YOU MUST EXERCISE! The movement from the exercise will aid your bowel movements and digestion.<br />
Taking fibre pills with out good amounts of exercise can cause the fibre pills to cause blockage as they turn into concrete / cement inside your gut.<br />
I am curious why someone between the ages of 18-21 is taking fibre pills. Short of a diagnosed bowel or intestinal condition, you should not need them. (assuming you are eating good food and getting normal amounts of exercise).