Constipation is a frequent complaint and corresponds to various symptoms such as irregular voiding, sensation of incomplete, painful or forceful voiding, hard stools and abdominal discomfort. Incorrect diet can, in part, explain intestinal motility disorders or dyssynergic defecation .
The increase in the incidence of intestinal function disturbances is especially present in developed countries, since the industrialization of food provides access to products of greater conservation, which is accompanied by a reduction of fiber content . Furthermore, the population has adopted a sedentary life style, which is associated with an inadequate diet and results in constipation.
Increased consumption of foods rich in fiber, such as, vegetables, fruit, and whole grain products, make up the primary treatment for constipation, besides the recommendation of an adequate ingestion of liquid (basically water) and the practice of physical activity . Studies have shown that food high in fibers, such as, resistant starch, pectin (fruit) and (hemi) cellulose (grains and cereals) promote an improvement of intestinal peristalsis and an increase in fecal weight, all acting as natural laxative . Polydextrose is a polysaccharide that is partially fermented in the large intestine, but is not digested or absorbed by the small intestine, and a substantial part of it is excreted in the stool. It presents the same properties of fibers and promotes a shorter time passing through the intestines and improves the consistency of the stool [5, 6]. It also acts as a substrate for beneficial endogenous microbes, allowing an increase in their levels and activity in the intestinal lumen [7, 8].
Probiotics have been defined as live microorganisms which when administered in adequate amounts confer a health benefit on the host . They should be viable in the conditions of the gastric lumen and have the capability to adhere to the intestinal epithelium . Selected probiotic strains have been reported to aid in the prevention and treatment of diarrhea caused by rotavirus and/or antibiotic therapy, reduction in the concentration of enzymes which promote cancer, prevention and/or relief of allergic symptoms in children, normalization of bowel movements and stool consistency in individuals who are constipated .
To obtain these benefits, as a rule of thumb a dose of at least a billion colony forming units should be consumed daily. A probiotic preparation can consist of a single strain or a combination of strains and can be in association with other biologically active ingredients. Probiotics are often included in dairy products , since these foods provide a preferred growth medium for many of these microorganisms.
Currently, there is great interest in functional foods. There are, however, few studies that evaluate their effect on constipation. The use of probiotics hold great promise, and, among the microorganisms evaluated most are of Bifidobacterium and Lactobacillus. Two randomized studies using products containing Bifidobacterium lactis DN-173 010 showed a significant increase in the frequency of evacuation when compared to the control group [13, 14]. Also B. lactis HN019 has been shown, in a dose depended manner, to shorten intestinal transit in subjects with self reported long transit times .
Using Lactobacillus casei Shirota, Koebenick et al.  demonstrated an improvement of the symptoms associated with constipation in comparison to placebo. However, the results when using probiotics with children who are suffering from constipation are inconsistent. Bu et al. , showed that the use of Lactobacillus rhamnosus Lce35 increased evacuation frequency, however, there was no difference when compared to children who took oral laxatives. Two other studies [18, 19] showed no evidence of improvement with constipated children using probiotics.
The combination of a prebiotic and probiotics would have a potentially synergic effect on the intestinal transit, as has been shown . The present study therefore aimed to investigate the combination of polydextrose L. acidophilus NCFM® and B. lactis HN019 in a yogurt on intestinal transit in subjects who suffer from constipation.