Bitter herbs are thought to stimulate digestive function by increasing saliva production and promoting both stomach acid and digestive enzyme production.⁴ As a result, they are particularly used when there is low stomach acid but not in heartburn (where too much stomach acid could initially exacerbate the situation). These herbs literally taste bitter. Some examples of bitter herbs include greater celandine, wormwood, gentian,dandelion, blessed thistle, yarrow, devil’s claw, bitter orange, bitter melon, juniper, andrographis, prickly ash, and centaury.⁵. Bitters are generally taken either by mixing 1–3 ml tincture into water and sipping slowly 10–30 minutes before eating, or by making tea, which is also sipped slowly before eating.

Boldo has been used in South America for a variety of digestive conditions, although this may have stemmed from its impact on intestinal infections or liver function. Studies specifically showing a benefit from taking boldo in people with indigestion and heartburn have not been performed. Picrorhiza, from India, has a similar story to that of boldo. While it is clearly a bitter digestive stimulant, human studies to confirm this have not yet been completed.