Is there supporting evidence for acacia powder being a prebiotic?Updated 6 months ago

There is indeed. 

So far, clinical studies have shown acacia fibre (also known as gum arabic) promotes the growth of healthy bacteria in the human digestive system. 

In a clinical trial, doses of 10 g of acacia fibre daily led to a significant increase in Bifidobacteria and Lactobacilli - two highly beneficial strains of flora, and the prebiotic effect was more potent than the same dose of inulin which is a commonly used prebiotic fibre. 

A similar prebiotic effect was shown in another study, which suggested that acacia fibre can help improve stool type and regularity.

 An in-vitro study from 2021, showed acacia fibre to have similar benefits in terms of promoting the growth of beneficial bacteria, as well as inhibiting the growth of Clostridium histolyticum which is commonly associated with dysbiosis.