Although it is generally advised to eat "raw" sources of fiber such as vegetables, the fast-paced work environments nowadays may not give us the required time to snack on vegetables often, so dietary fiber supplements are the logical choice in these situations, as they're usually comfortable and fast to eat even at your workplace.
Keep in mind that usually these supplements are only sources of soluble fiber, so you'll have to integrate the insoluble fibers when you're home for optimal health benefits.
We've already seen in the health benefits section that dietary fiber supplements are usually beneficial in reducing symptoms of IBS and even autoimmune diseases such as Crohn's Syndrome. Additional reasons why you may want to consume them are increased weight loss, decreased cholesterol and lower risk of developing colon cancer.
In addition, prebiotic supplements such as inulin and oligosaccharides have also been shown to be effective against Clostrudium difficile and ulcerative colitis.
Despite there being dozens of different dietary fiber supplements, most of them have never been approved by the FDA or by independent scientific studies, so we'll just stick to the most proven and effective.
These husks are derived from the seed of the Plantago ovata, a plant native of India. Its seeds, when ground and wet, become mucilaginous and increase their volume by absorbing water. Psyllium is indigestible to humans, so it will steadily pass through the digestive tract, providing a constant level of bulk and volume despite the rest of your diet. This regularity has been shown to alleviate the symptoms of several inflammatory diseases of the digestive tract (including Irritable Bowel Syndrome and Crohn's Disease).
Psyllium husks, when used daily, have also been shown to lower LDL ("bad cholesterol") levels and to stabilize blood glucose levels (lowering the risk of developing type 2 diabetes).
Commercially, they are very easily available at affordable prices, with brand names such as Metamucil, Serutan, Fybogel.
Inulins are the industrially-extracted polymers of fructose (a carbohydrate naturally found in fruits): they are oligosaccharides and as such have some nutritional value (around 1Cal per gram). Due to its sweet taste and healthy properties, inulin is widely used as a substitute for sugars and flour in commercial cakes as well as a smoothener in powdered supplements.
Inulins are pre-biotic fiber sources, meaning that they are processed by our gut flora, and their by-products have additional health benefits: they are processed into short-chain fatty acids that have been shown to not only have anti-inflammatory properties (reducing several symptoms such as diarrhea, constipation and flatulence), but also to increase the absorbing capacity of the cells lining the colon wall (via increased expression of some transport-related genes), resulting in an increased absorption of important minerals such as iron, magnesium and calcium.
In addition, their availability to the gut flora has been shown to improve the amount and vitality of beneficial bacteria such as Lactobacillus and Bifidobacterium. This last property is particularly useful after antibiotic therapies, that usually kill most of the aforementioned beneficial bacteria.
The most recent discovery in dietary fiber supplements involves vegetable gums, such as guar and acacia. They are usually sold in powder and have been shown to be effective against irritable bowel syndrome.