egetarian and total plant-based diets (vegan diet)
have gained much attention for their positive effects in promoting
healthy lives and in the prevention and treatment of
certain diseases (1-3). Conditions including obesity, diabetes
mellitus, dyslipidemia, atherosclerotic cardiovascular
disease, cancer, and a variety of gastrointestinal disorders
have been improved in persons consuming these diets
(2-4). Some of the aforementioned effects are secondary
to changes in multiple parameters, including reduction in
body weight, improved insulin sensitivity, modulation of
gut hormones, and decreased inflammation (2). Although it
is possible that many of the beneficial effects of vegetarian
and plant-based diets can be attributed to their high-fiber
content, the extent to which the contribution of fiber contained
in such foods is linked to the positive health outcomes
remains unknown (5-10).
Fiber present in food is classified into insoluble and
soluble fiber (Fig. 1). Insoluble fiber is composed of nonstarch
polysaccharides (such as cellulose) that are nondigestible
by enzymes secreted in the gastrointestinal tract;
they are usually nonfermented in the colon and do not dissolve
in the aqueous phase (2). In contrast, soluble fibers
are complex polysaccharides that may contain charged
molecules. Soluble fibers, such as pectin or inulin, are also