In this study, an extract of kiwifruit (Kivia powder) containing Zyactinase™ was investigated for its ability to improve bowel function and satisfaction in subjects with occasional constipation. Bowel function was determined using various endpoints, including the number of bowel movements, and bowel health was based on endpoints such as satisfaction, abdominal bloating and discomfort, burping, and flatulence. Improvements were noted in the number of bowel movements, with increased bowel movements in the group using the studied extract. There were also improvements observed in bowel health and stool formation. This suggests that Kivia powder improved bowel habits in this group of subjects.
Chronic constipation is often dealt with by a physician with recommendations for over-the-counter medications such as bulk-forming laxatives, stimulants, stool softeners, lubricants, or osmotics. Although individuals suffering from occasional constipation also have access to and use these agents, with or without knowledge of their physicians, many individuals might prefer the option of an effective natural agent for occasional use. Given the high costs associated with the diagnosis and treatment of constipation  in conjunction with considerable prevalence rates noted in the literature , it is clear that these products would be of interest to consumers. High-fiber food products and supplements containing psyllium or flax, as well as aloe and probiotics, are sold and used for this purpose and have been investigated in clinical trials [6–8]. Kivia powder containing Zyactinase™ is a freeze-dried powder from kiwifruit (Actinidia deliciosa var. deliciosa (C.F. Liang and A.R. Ferguson), containing the enzyme actinidin, plant polyphenols, dietary fiber, carbohydrates, and oligosaccharides. Although the potential mechanism of action for its anticonstipative effects are not yet completely clear, kiwifruit extract is rich in enzymes able to aid in digestion, such as actinidin, as well as oligosaccharides, which may act as prebiotics, enhancing the growth of beneficial bacteria in the gastrointestinal tract. Additionally, in vitro, Zyactinase™ significantly increased the growth of the probiotic bacteria Lactobacillus reuteri, Lactobacillus acidophilus, Pediococcus acidilactici, and Lactobacillus planetarium, further supporting its prebiotic role in the gut . In this study Kivia aided gentle laxation without urgency whilst promoting normal stool formation, making the product ideally suited as an over the counter medication for occasional constipation.
Although strong published human and animal data are lacking at this time, unpublished data suggest that use of the fruit decreased constipation in elderly patients in New Zealand. Also, in an earlier clinical study, Kivia was found to promote bowel movement, improve discomfort in the abdomen, and improve quality of life in elderly patients in Japan . Like the study by Uebaba et al., our study also suggests improvement in the number of bowel movements. Further research is required in order to compare our results with those of others.
The main endpoints of this study included the number of spontaneous and complete spontaneous bowel movements. Both spontaneous and complete spontaneous bowel movement frequency increased between groups and compared to baseline and these improvements are likely due to the multiple effects of the extract on bowel health as described above. Secondary endpoints of this study included abdominal bloating, abdominal discomfort or pain, satisfaction with bowel habits, flatulence, burping, stool form and bowel urgency. Abdominal bloating, abdominal discomfort or pain, and satisfaction with bowel habits demonstrated significant decreases from baseline. In addition, abdominal pain or discomfort and flatulence were significantly lower in the treatment group than in the placebo group. Stool form was also improved as proven by the decrease in stool form 1 and 2, which are characteristic stool of people with constipation, and an increase in stool form 3 and 4, the optimal stool form, in the treatment group. These results suggest that Kivia may be of assistance in other gut conditions related to these secondary gut health parameters such as irritable bowel syndrome and chronic constipation, but that will require further study.
Regarding within group change over time, satisfaction and abdominal bloating did not improve significantly in either group. However, abdominal bloating steadily decreased and satisfaction steadily increased in both groups nonsignificantly with time. This suggests that taking part in the study itself may have allowed for some placebo-related benefits and that additional benefits of the product were not obvious. Also, expectations play a role in satisfaction, and the expectations of the study product may have been high. It is interesting to note the strong placebo effect so often reported with gut health studies and that not only did bowel movements increase but also that the stool features also improved in the placebo group albeit not as much as the active group
Bowel movement frequency is an objective endpoint and easily quantified compared to subjective feelings of associated symptoms. It is a common misconception that normal bowel habits involve daily excretion  and this misconception may have contributed to a lack of improvement in satisfaction despite increased bowel movements. Furthermore, since subjects were not screened and selected based on secondary gut health parameters, variability within our sample along these endpoints would have contributed to decreased room for improvement thus any improvement is noteworthy and lends credence to further exploration.
Another limitation of this study was that the subjects were not specifically chosen based on gut health parameters such as bloating, pain, and flatulence. Given that these symptoms are also associated with irritable bowel syndrome, future studies should screen for these symptoms and only subjects with certain levels of these symptoms should be included. Thus, further research is required to evaluate the impact of the Kivia powder product on a population of subjects who would be specifically selected for their baseline level of other gut health parameters (bloating, pain, flatulence, burping, etc.) to determine the true impact of the product on these symptoms.
In conclusion, this proprietary extract of kiwifruit, containing Zyactinase™, significantly increased the number of spontaneous and complete spontaneous bowel movements after four weeks when compared to placebo. Gut health parameters associated to constipation also improved from baseline and within groups. In addition, the product was well tolerated at the daily-administered dose of one sachet (containing 5,500 mg of Zyactinase™). Also, the decreased use of rescue medication in the treatment group, already lower than in the placebo group at baseline, suggests that the product was helpful in this group of individuals. The results of this study suggest that this product may be of interest to generally healthy adults with occasional constipation and associated abdominal discomfort.