Vitamin pills are made up of a number of ingredients, some of which are the vitamins and minerals themselves -- the "active" ingredients -- and some of which don't contribute nutritional value, but have other roles. These so-called "inactive" ingredients bind the vitamins together, give them color, and increase shelf life. Cellulose, specifically, is a bulking and binding agent.
If you've seen cellulose listed among the inactive ingredients in your vitamin pills, you've probably wondered what it's doing there. Cellulose is the chemical name for fiber, and fiber is made up of long chains of sugar molecules -- glucose, to be precise. While your cells can use glucose for energy, you can't access the glucose in cellulose, because you have no enzymes able to break the glucose molecules apart from one another, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry."
Cellulose in Vitamins
In vitamins, cellulose serves the important role of helping to combine vitamins -- some of which would otherwise be liquids -- into a single cohesive pill. This makes the vitamins easier to swallow, and more importantly, ensures that you're getting the right dose. The dosage of some vitamins is so small that it would be impossible to measure out the appropriate quantity if it weren't prepackaged into a single pill.
Fiber is important to digestion, explains Dr. Lauralee Sherwood in her book "Human Physiology," and helps to increase the bulk of material moving through the digestive tract. This increases the efficiency of intestinal function, helping to keep you regular. Further, cellulose or fiber binds to cholesterol and certain toxins, which helps keep you from absorbing them into the bloodstream. This, coupled with the fact that you stay more regular when you consume fiber, means cellulose helps decrease your risk of colon cancer.
Cellulose does have many positive effects on your body, but unfortunately, not in the small dosage you get from the quantity in your vitamin pills. According to the Institute of Medicine, you need about 25 grams of fiber per day if you're female and younger than 50, 21 grams per day if you're over 50. Men under 50 need 38 grams per day, while men over 50 need 30 grams. Vitamin pills have less than a gram of cellulose in them, so while it contributes to the fiber you get each day, the contribution is minimal, and by itself, this fiber has no measurable effect.