Drinking a beverage containing acetic acid every day may increase bowel movement frequency in people with mild constipation. Japanese researchers reached this conclusion in a randomized, double-blind, placebo-controlled study accepted for publication in Scientific Reports.
The study included 44 healthy Japanese adults aged 20 to 69 who experienced mild constipation. For four weeks, 22 participants drank 200 ml of a beverage containing 750 mg of acetic acid every morning with breakfast. The remaining participants received a placebo containing 30 mg of citric acid. Their usual diet and lifestyle were not changed during the study.
Participants recorded their bowel movement frequency and other stool characteristics every day. After four weeks, those who consumed the acetic acid drink had bowel movements approximately 1.2 times more often per week, on average, than participants in the placebo group. Some improvements, including a greater stool volume and more days with bowel movements, were observed as early as the first week.
However, the researchers found no significant changes in the diversity of the participants' gut microbiota. They therefore suggested that the effects of acetic acid may not be related to changes in the composition of gut bacteria. Instead, the drink could potentially enhance the gastrocolic reflex—the body's natural response to eating that stimulates intestinal activity. However, this mechanism was not directly investigated and remains a hypothesis.
The authors emphasize that the findings do not yet provide evidence that acetic acid drinks are a universal treatment for constipation. The study was small, involving only 44 participants, all of whom were healthy Japanese adults with mild constipation. In addition, bowel movements and stool characteristics were self-reported by the participants.
The researchers also tested only one dose of acetic acid and did not control the participants' diets. Larger studies are therefore needed to confirm the effect and determine whether there is an optimal dose for improving bowel function.
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