Quick Summary
Annatto (Bixa orellana) is a plant traditionally used as a natural colorant. Its seed-derived compound, bixin, has been studied for various pharmacological potentials. Current clinical evidence on annatto itself in humans is limited. Some clinical trials have explored its use as a photosensitizer in antimicrobial photodynamic therapy for halitosis treatment, showing short-term benefits. Preclinical studies suggest bixin has antioxidant, anti-inflammatory, antimicrobial, and protective effects in various organ systems, but clinical evidence remains insufficient. Overall, research on annatto is preliminary, with more robust human studies needed.
What is it
Annatto is a tropical shrub native to Central and South America. It is widely known for its seeds, which are the source of natural orange-red pigments used as food colorants. The seeds contain carotenoids, including bixin, which contribute to the plant’s distinctive color and are the focus of ongoing pharmacological research.
Traditional Uses
Traditionally, annatto seeds have been used primarily as natural dyes and food colorants. Some cultures have also employed annatto extracts for their antimicrobial properties and minor medicinal purposes, though such uses are less well documented scientifically.
Active Compounds
- Bixin: A major apocarotenoid carotenoid from annatto seeds, studied for its biological activity.
- Other carotenoids and essential oils: Contribute to annatto’s color and potential bioactivity.
Potential Benefits with Evidence Levels
- Intraoral halitosis treatment (Low to moderate clinical evidence): Antimicrobial photodynamic therapy using annatto extracts as photosensitizers may reduce harmful oral bacteria and volatile sulfur compounds, temporarily improving bad breath.
- Anti-inflammatory and antioxidant effects (Preclinical evidence): Bixin has shown antioxidant and anti-inflammatory activities in lab and animal studies, suggesting neuroprotective, hepatoprotective, nephroprotective, and photoprotective potential.
- Joint inflammation reduction (Pilot human clinical trial): A small study of a multi-herb supplement including annatto suggested reduced inflammation markers in runners with knee pain; the specific effect of annatto remains unclear.
- Antimicrobial effects (In vitro and preliminary in vivo evidence): Annatto essential oils demonstrated activity against Leishmania amazonensis in lab and animal studies, indicating potential antiparasitic properties.
- Bioactive natural colorant applications (Industry and formulation research): Annatto-derived carotenoids are widely used as natural colorants and are being researched to improve stability and delivery for therapeutic and cosmetic uses.
Side Effects
Clinical trials and toxicological studies generally report a favorable safety profile for annatto and its derivatives at tested doses. No significant adverse effects have been consistently documented in humans. Some mild, transient effects such as salivation were reported in animal studies with related natural dyes. Comprehensive safety data, particularly for long-term, high-dose use, is limited.
Drug Interactions
No direct clinical evidence exists regarding drug interactions with annatto or its constituents. Due to the presence of carotenoids and other bioactive compounds, caution is advised until pharmacokinetic and interaction studies are available.
Who Should Avoid It
- Individuals who are pregnant or breastfeeding should exercise caution, as no safety data are available for these populations.
- People with known allergies or sensitivities to annatto or related natural pigments may want to avoid use.
- Those on medications should consult healthcare providers before use due to unknown interaction potential.
Evidence Limitations
Most evidence for annatto’s benefits is derived from preclinical studies, in vitro experiments, or small pilot clinical trials often involving combination supplements. Large, well-designed randomized controlled trials of isolated annatto or bixin in humans are lacking. Clinical trials involving annatto in antimicrobial photodynamic therapy have short follow-up periods and methodological variability. Additionally, long-term safety data, particularly for high doses and vulnerable populations such as pregnant or breastfeeding women, remain insufficient. Consequently, the current evidence base is preliminary and does not support definitive health claims.
References
- Wiench R, Fiegler-Rudol J, Zięba N, Misiołek M. Laser Interventions for Intraoral Halitosis: A Systematic Review of Randomized Controlled Trials. (2025)
- Motta PB et al. Short term effect of antimicrobial photodynamic therapy and probiotic L. salivarius WB21 on halitosis: A controlled and randomized clinical trial. (2024)
- Hashmi AR et al. Bixin Beyond Colour: Expanding Therapeutic Horizons Through the Integration of Pharmacological Potential with Modern Drug Design and Delivery Strategies. (2026)
- González-Gross M et al. Analysis of Effectiveness of a Supplement Combining Harpagophytum procumbens, Zingiber officinale and Bixa orellana in Healthy Recreational Runners with Self-Reported Knee Pain: A Pilot, Randomized, Triple-Blind, Placebo-Controlled Trial. (2021)
- de Lara da Silva CE et al. Effect of essential oils on Leishmania amazonensis: a systematic review. (2020)
- Park JS et al. Nonclinical safety evaluation of food colorant lac dye via systematic toxicity profiling with assessment of in vivo antigenic potential. (2022)
Last Reviewed
June 2024
Disclaimer: This page is for informational purposes only and does not constitute medical advice. Annatto and its constituents have been studied for various biological effects, but current evidence is limited and does not support conclusive health claims. Consult a healthcare professional before using annatto supplements or treatments, especially if you are pregnant, breastfeeding, have underlying health conditions, or are taking medications.