Bitter herbs are thought to stimulate digestive function by increasing saliva production and promoting both stomach acid and digestive enzyme production.⁷ 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.⁸. 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.

Some bitters widely used in traditional medicine in North America include yarrow, yellow dock, goldenseal, Oregon grape, and vervain. Oregon grape’s European cousin barberry has also traditionally been used as a bitter. Animal studies indicate that yarrow, barberry, and Oregon grape, in addition to stimulating digestion like other bitters, may relieve spasms in the intestinal tract.⁹

Due to of its supposed antimicrobial activity, goldenseal has a long history of use for infectious diarrhea. Its major alkaloid, berberine (also found in barberry and Oregon grape), has been shown to improve infectious diarrhea in some double-blind trials.¹⁰ Negative studies have generally focused on people with cholera, while positive studies investigated viral diarrhea or diarrhea due to strains of E. coli. These studies generally used 400–500 mg berberine one to three times per day. Because of the low amount of berberine in most goldenseal products, it is unclear how effective the whole root or root extracts would be in treating diarrhea.

Herbs that support a person’s immune system in the fight against microbes and directly attack microbes include the following: barberry, echinacea, elderberry, goldenseal, licorice, Oregon grape, osha, and wild indigo.

Berberine is derived from several plants, including barberry, Oregon grape, goldenseal, and goldthread (Coptis chinensis). Preliminary trials have shown that berberine can be used successfully to treat giardia infections.^11,12 In addition, test tube studies show that berberine kills amoebae, although it is not known whether this effect occurs in humans.¹³ The amount required is approximately 200 mg three times per day for an adult—a level high enough to potentially cause side effects. Therefore, berberine should not be used without consulting a healthcare provider.

An ointment containing Oregon grape (10% concentration) has been shown in a clinical trial to be mildly effective against moderate psoriasis but not more severe cases.¹⁴ Whole Oregon grape extracts were shown in one laboratory study to reduce inflammation often associated with psoriasis.¹⁵ In this study, isolated alkaloids from Oregon grape did not have this effect. This suggests that there are other active ingredients besides alkaloids in Oregon grape. Barberry, which is very similar to Oregon grape, is believed to have similar effects. An ointment, 10% of which contains Oregon grape or barberry extract, can be applied topically three times per day.

Goldenseal is reputed to help treat many types of infections. It contains berberine, an alkaloid that may prevent UTIs by inhibiting bacteria from adhering to the wall of the urinary bladder.¹⁶ Goldenseal and other plants containing berberine (such as Oregon grape) may help in the treatment of UTIs. These herbs have not, however, been studied for the treatment of UTIs in humans.

Berberine is an alkaloid found in various plants, including goldenseal, barberry, Oregon grape, and goldthread. Berberine exhibits a broad spectrum of antibiotic and antifungal activity in test tube, animal, and human studies.^17,18 Berberine has shown effective antidiarrheal activity in a number of diarrheal diseases,^19,20,21 and it may offer the same type of relief for the diarrhea seen in patients with chronic candidiasis. Doctors familiar with the use of berberine-containing herbs sometimes recommend taking 2 to 4 grams of the dried root (or bark) or 250 to 500 mg of an herbal extract three times a day. While isolated berberine has been studied, none of these herbs has been studied in humans with chronic candidiasis.

Berberine is an alkaloid found in various plants, including goldenseal, barberry, Oregon grape, and goldthread. Berberine exhibits a broad spectrum of antibiotic and antifungal activity in test tube, animal, and human studies.^22,23 Berberine has shown effective antidiarrheal activity in a number of diarrheal diseases,^24,25,26 and it may offer the same type of relief for the diarrhea seen in patients with chronic candidiasis. Doctors familiar with the use of berberine-containing herbs sometimes recommend taking 2 to 4 grams of the dried root (or bark) or 250 to 500 mg of an herbal extract three times a day. While isolated berberine has been studied, none of these herbs has been studied in humans with chronic candidiasis.

Goldenseal and Oregon grape contain the antibacterial constituent known as berberine. While topical use of berberine in eye drops has been clinically studied for eye infections,²⁷ the use of the whole herbs has not been studied for conjunctivitis or blepharitis.