Black psyllium (Plantago indica), like the more commonly used blonde psyllium (Plantago ovata), is a source of soluble fiber that forms a gel when mixed with water. Its main mechanism in supporting gastrointestinal health is via its bulking and stool-softening effects, which can help regulate bowel movements. There is moderate scientific evidence suggesting that psyllium fiber in general can help alleviate symptoms associated with gas and bloating, primarily by improving stool consistency and promoting regularity. Several clinical studies with psyllium husk (not always specifying black vs. blonde) have reported reductions in bloating and discomfort in patients with irritable bowel syndrome (IBS) and chronic constipation.

The mechanism by which psyllium may reduce bloating is believed to involve normalizing bowel transit and reducing the stagnation of intestinal contents, which can otherwise lead to excessive fermentation and gas production. Some individuals, however, may initially experience increased gas when first using psyllium, as their gut bacteria adapt to the increased fiber.

While most research does not specifically differentiate between black and blonde psyllium, their similar fiber profiles suggest comparable effects. Overall, the evidence base is stronger for general psyllium fiber than for black psyllium specifically, and most findings are extrapolated from studies on Plantago ovata. Thus, the scientific support is moderate, warranting a rating of 3.