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Bitter kola

A bitter seed from West and Central Africa, chewed fresh. Small trials in people have studied it for knee arthritis pain and eye pressure, and it changed how the body handled the malaria drug quinine.

Traditional use

Native to West and Central Africa, where it has a place in social ceremonies as well as in medicine. In a 2026 survey of 152 Nigerians, mostly Ibibio, Annang and Igbo, people chewed the fresh seed mainly for respiratory symptoms, stomach upset and general well-being. It is a different plant from the kola nut (Cola species).

What studies show

  • Limited

    Knee osteoarthritis: a six-week trial in Nigeria (84 people finished) compared bitter kola extract with placebo and two anti-inflammatory drugs. Pain and walking improved more than on placebo, but relief was slower and shorter than with the drugs. One small trial; the authors called for more studies.

  • Limited

    Eye pressure: in 46 healthy young adults in Ghana, a single dose of bitter kola by mouth lowered eye pressure over the next two hours. A separate trial of bitter kola eye drops in people with glaucoma found them about as effective as the drug timolol over 24 weeks. Both are single studies.

Be careful of

Cautions

  • InteractionIn healthy Nigerian volunteers, eating bitter kola daily for a week lowered blood levels of the malaria drug quinine taken with it. Keep it apart from quinine, and ask about other medicines.
  • NoteIts safety over long periods has not been studied in people. The knee trial reported no heart, kidney or drug reactions over six weeks.
  • PregnancyThere is no safety information for pregnancy or breastfeeding.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

Sources

  1. Clinical effects of Garcinia kola in knee osteoarthritis (J Orthop Surg Res, 2008) (opens in a new tab) · NIH · read September 25, 2026
  2. Oral consumption of Garcinia kola (Bitter kola) lowers intraocular pressure (Acta Ophthalmol, 2020) (opens in a new tab) · NIH · read September 25, 2026
  3. Effect of dehusked Garcinia kola seeds on the overall pharmacokinetics of quinine in healthy Nigerian volunteers (J Clin Pharmacol, 2015) (opens in a new tab) · NIH · read September 25, 2026
  4. Efficacy of Garcinia kola 0.5% Aqueous Eye Drops in Patients with Primary Open-Angle Glaucoma or Ocular Hypertension (Middle East Afr J Ophthalmol, 2010) (opens in a new tab) · NIH · read September 25, 2026
  5. Traditional use of Garcinia kola Heckel in Nigeria - the results of questionnaire survey compared with scientific evidence (2026) (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.