Annatto

Annatto (Bixa orellana L.): A Comprehensive Reference

1. Identity and Botanical Description

Botanical and Common Names

Bixa orellana L., commonly known as annatto or the lipstick tree, is an evergreen shrub from the family Bixaceae. Annatto is an orange-red condiment and food coloring derived from the seeds of the achiote tree (Bixa orellana), native to tropical parts of the Americas. The plant carries a wide variety of vernacular names. The name "annatto" is the most common around the world, adopted from a Carib language, while the plant's scientific name, Bixa orellana, comes from the word bija or biché, another name given by Carib indigenous people, and was named in honor of Francisco de Orellana, a Spanish explorer of the Amazon River. The Maya called it Kiwi', but the Spaniards named it achiote, from the Nahuatl word axiotl. Annatto is believed to originate from Brazil, where it is known as urucum. In the Philippines, it is called atsuete and is used as food coloring in traditional dishes.

Natural Source and Cultivation

Native to tropical regions of Central and South America, it is now cultivated globally. Annatto (Bixa orellana), which originated from Central America, is now widely grown throughout the tropical regions of the world, including West Africa. Peru is the largest exporter of annatto seed, exporting approximately 4,000 tons annually; Brazil is the largest producer, with about 5,000 tons. Kenya exports approximately 1,500 tons of annatto seed and extracts annually and is the second-largest exporter after Peru.

Common Forms and Preparations

The condiment is typically prepared by grinding the seeds to a powder or paste. Similar effects can be obtained by extracting some of the color and flavor principles from the seeds with hot water, oil, or lard, which are then added to food. The pigment may be suspended in water or oil, or dried into a powder. Uses for annatto extract include coloring and dyeing in foods, medicines, and cosmetics. The pigment is extracted from the pericarp of the seeds through use of alkaline water, vegetable oil, or organic solvents. Together, the pigments bixin and norbixin are collectively known as annatto and are utilized extensively in the food industry under the designation E160b as natural food colorants. It is used to impart a yellow to red-orange color to foods, but may also impart a sweet, peppery flavor.

The main product from B. orellana is an organic dye present in the seed coat called "annatto," which is lipid-soluble and widely used in the food industry for its red to orange-yellow colors, appearing in foods such as cheese, butter, oils, margarine, ice cream, pastries, soft drinks, soup, and rice. The annatto pigment has global economic significance, as it is one of the most widely used natural dyes to color food, cosmetics, and pharmaceutical products.

2. Traditional and Historical Use

Pre-Columbian Indigenous Cultures

The earliest uses of the seeds, referred to as Achiotl in ancient Latin cultures, can be traced back to indigenous populations found throughout the Amazon and were later noted in the Mayan, Aztec, and Incan civilizations. It was probably not initially used as a food additive, but for other purposes, such as ritual and decorative body painting (still an important tradition in many Brazilian native tribes, such as the Wari'), sunscreen, insect repellent, and for medical purposes. The Aztecs and other indigenous people living in Mexico, Central America, and South America used annatto to make fabric dyes and red body paint. They also used it to make lipstick, which is where achiote gets its other name: the "lipstick tree."

Men of the Tsàchila tribe in Ecuador are highly recognizable thanks to their traditional bright orange hair, which is achieved by using crushed seeds of annatto. It is believed they have been doing so for centuries. In pre-Hispanic times, annatto was mostly used as a dye for food, skin, fabrics and, along with cochineal, it was also used for manuscript painting, at least up to the sixteenth century.

Traditional Medicinal Uses

In ancient times, people used leaves, roots, and seeds as medicines, including to heal wounds, cure diarrhea, and treat asthma. The seeds of this plant have purgative, anti-pruritic, and buccal tumor-treating properties. The decoction of leaves from B. orellana is used for gastric ulcers, stomach discomforts, colic, and oral and throat inflammation. The plant is used for treatment of indigestion and infectious diseases. It has also been used for fever, skin problems, intestinal problems, and hepatoprotection by various tribal communities worldwide. It is also employed as an antidote to bites and as an insect repellant.

Despite the different cultures and traditions among countries in South and Central America, several of the popular uses of Bixa orellana are the same, for example: antipyretic, aphrodisiac, antidiarrheal, antidiabetic, and insect repellent. Beyond its industrial applications in food, cosmetics, leather, and solar cells, B. orellana has traditional medicinal uses for treating conditions like gonorrhea, asthma, and sore throats. In French Guiana, syrup made from the fruit is used to treat inflammatory conditions.

Spread to Europe and Asia

Annatto has been traditionally used as both a coloring and flavoring agent in various cuisines from Latin America, the Caribbean, the Philippines, and other countries where it was taken home by Spanish and Portuguese colonizers in the 16th century. Annatto seeds were brought to Asia from Mexico in the 17th century through Sephardic Jewish trade routes. The use of annatto seeds to dye food began when settlers arrived in the Americas and could not find saffron to use as coloring in their recipes. Annatto seeds were soon referred to as "poor man's saffron," and their popularity in Europe grew immensely, leading to the commercial cultivation of the spice in India by 1787. The seeds continued to expand in use as European cheesemakers added dye derived from the seeds to low-quality cheeses to mimic the yellowish hue that higher-quality grass-fed cheeses would produce. This tradition continues in the present day with many different kinds of cheese and dairy products.

In India, annatto is known as "sindoor" and is considered auspicious for married women. Applying annatto to the forehead next to the hairline indicates that a woman is married.

Culinary Traditions

In Venezuela, annatto is used in the preparation of hallacas, huevos pericos, and other traditional dishes. In Puerto Rico, it is often simmered in oil or ground with seasonings and herbs to make sazón or used to make pasteles, arroz con gandules, and several other dishes where it is one of the main ingredients. Annatto paste is an important ingredient of cochinita pibil, the slow-roasted pork dish popular in Mexico. It is also a key ingredient in the drink tascalate from Chiapas, Mexico.

3. Key Constituents and Active Compounds

Primary Pigments: Bixin and Norbixin

The color of annatto comes from various carotenoid pigments, mainly bixin and norbixin, found in the reddish waxy coating of the seeds. The seeds contain 4.5–5.5% pigment, which consists of 70–80% bixin. Bixin is responsible for imparting reddishness, and norbixin is responsible for imparting yellow.

Bixin consists of a chain of 25 carbons and has the molecular formula C₂₅H₃₀O₄ (MW = 394.51). It has a carboxylic acid and methyl ester group at the ends of the chain. Bixin occurs in nature as 16-Z (cis), but during the extraction process it isomerizes resulting in the 16-E form (trans), which is called isobixin. Bixin belongs to the small class of natural apocarotenoids, whose formation occurs by the oxidative degradation of C40 carotenoids. It is a polyunsaturated norcarotenoid.

The seeds of B. orellana contain two major carotenoid compounds: bixin, which is oil-soluble, and its water-soluble counterpart norbixin, which results from the alkaline hydrolysis of bixin. The chemical formula of norbixin is C₂₄H₂₈O₄. This dual solubility property of annatto is rare for carotenoids. Unlike beta-carotene, another well-known carotenoid, annatto-based pigments are not vitamin A precursors.

Tocotrienols

Tocotrienols are derived from three major sources, including rice, palm, and annatto. Annatto is the only tocopherol-free source of tocotrienols. Annatto tocotrienol typically contains approximately 90% delta- and 10% gamma-tocotrienol. Tocotrienols are vitamin E molecules that differ from tocopherols by possessing an unsaturated isoprenoid side chain. They are more lipophilic, making them more easily incorporated into the cell membrane and more rapidly absorbed than tocopherols. Among all eight vitamin E isomers, δ-tocotrienol is considered the most potent antioxidant and anti-inflammatory agent.

Additional Phytochemicals

More than two dozen substances have been isolated from the seeds of Bixa orellana. Besides bixin and norbixin, other compounds such as isobixin, beta-carotene, cryptoxanthin, lutein, zeaxanthin, orellin, bixein, bixol, crocetin, ishwarane, ellagic acid, salicylic acid, threonine, tomentosic acid, tryptophan, and phenylalanine have been found in the seeds of annatto. In addition, the following compounds are found in these seeds in their respective concentrations: 40 to 45% cellulose, 3.5 to 5.5% sugars, 0.3 to 0.9% essential oils, 3% fixed oils, 1.0 to 4.5% pigments, and 13 to 16% proteins, as well as alpha and beta-carotene, tannins, and saponins. The major oily constituent of annatto seeds is geranylgeraniol, representing 1% of dry seeds.

4. Mechanisms of Action

Antioxidant Mechanisms

In the food production industry, active packaging films incorporating annatto byproducts have been shown to delay lipid oxidation, thereby extending shelf life through antioxidant mechanisms. Because of its antioxidant, anticancer, analgesic, hypoglycemic, antibacterial, antidiarrheal, and anti-inflammatory characteristics, the pigment bixin has been used in several therapeutic applications. The antioxidant activity of bixin includes direct free radical scavenging and induction of endogenous antioxidant enzyme systems. It has been documented that bixin increases mRNA expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream genes.

Anti-Inflammatory Mechanisms

Bixin has been shown to inhibit the TLR4/NF-κB signaling pathway, reducing NF-κB nuclear translocation and downstream production of pro-inflammatory cytokines, such as TNF-α and IL-6, in cell-based and animal experimental systems. Bixin also modulates the NLRP3 inflammasome by suppressing thioredoxin-interacting protein (TXNIP) expression, thereby reducing IL-1β secretion. Bixin causes down-regulation of protein and gene expression of TXNIP, NLRP3, ASC, caspase-1, IL-1β, and IL-18. The anti-inflammatory effects evoked by bixin may occur at least in part through modulation of the TXNIP/NLRP3 inflammasome pathway.

Cardiovascular and Lipid-Modulating Mechanisms

The effect of bixin in inhibiting in vitro human-isolated LDL oxidation was more potent (5–6-fold) than that of lycopene. Bixin has been shown to increase the activity of antioxidant enzymes in diabetic rats and reduce the inflammatory response and atherosclerotic plaques in hypercholesterolemic rabbits. These atheroprotective effects are mediated at least in part through activation of the Nrf2 and suppression of the NF-κB pathways in macrophages.

Hypoglycemic Mechanisms

It was concluded that Bixa orellana (annatto) lowers blood glucose by stimulating peripheral utilization of glucose, and it is possible that this glucose-lowering extract might be of pharmacological importance. The therapeutic properties of annatto, including its antioxidant and hypoglycemic properties, have been attributed to its high levels of carotenoids.

5. Scientific Evidence by Area of Use

5.1 Antioxidant Activity and LDL Oxidation

Some studies have demonstrated that bixin and norbixin have antioxidant and antiatherogenic potential in vitro and in animal models, but there was no evidence supporting the effects of their long-term or short-term consumption by humans prior to a 2019 human trial. The aim of that study was to evaluate the effects of short-term intake of annatto carotenoids on biochemical and oxidative stress biomarkers as well as on the susceptibility of LDL oxidation in healthy individuals, using lycopene as a positive control. Daily supplementation at 0.05 mg/kg of body weight with bixin, norbixin, lycopene, or placebo for 7 days was evaluated in a randomized, controlled crossover study in 16 healthy volunteers (8 men and 8 women).

In an earlier study, a single dose of norbixin reduced the postprandial levels of oxidized LDL (oxLDL), thiobarbituric acid reactive substances (TBARS), and the levels of proinflammatory cytokines after the consumption of a hypercaloric meal by healthy volunteers. Researchers hypothesized that annatto carotenoids improve the redox status of erythrocyte plasma membranes and promote a consequent increase in human erythrocyte resistance to hemolysis, given that erythrocytes exhibit high susceptibility to hemolysis in several pathologies due to the oxidation of cellular components. In an ex vivo arm of that study, healthy volunteers consumed a capsule containing bixin or norbixin (0.05 mg/kg body weight per day) or placebo for 7 days before blood sample collection.

Evidence strength: Human evidence is limited to small, short-term trials (≤16 participants, ≤7 days). In vitro and animal data are more robust, but clinical translation remains preliminary.

5.2 Cardiovascular Health and Lipid Parameters

Findings published in Clinical & Experimental Cardiology demonstrated that annatto tocotrienol — composed mainly of delta-tocotrienol — improved cardiovascular risk factors including inflammatory cytokines, nitric oxide (NO), and C-reactive protein (CRP). After only 4 weeks, of doses ranging from 125–750 mg/day, an optimum of 250 mg/day along with a healthy diet decreased inflammatory and oxidative stress markers significantly. These results suggest delta-tocotrienol is a potential candidate for therapeutic applications in maintenance of health and protection from aging diseases, concluded the researchers. Of doses ranging from 125–750 mg/day, an optimum of 250 mg/day, along with a healthy diet, decreased lipid levels significantly after only 4 weeks. Higher doses did not reduce lipid levels but may be useful for other, non-cardiovascular clinical applications. Notably, throughout the 30-week study period, no adverse events were reported for any of the dosages.

In a rat model of streptozotocin-induced diabetes, blood glucose, LDL cholesterol, and triglyceride levels were reduced in the diabetic rats treated with bixin. Bixin treatment also prevented protein oxidation and nitric oxide overproduction and restored superoxide dismutase activity.

Evidence strength: There is a small but growing clinical dataset for annatto-derived tocotrienols on cardiovascular biomarkers, though published human trials are limited in number and scale. Animal evidence for bixin on lipid metabolism is more extensive. Independent replication in large, randomized, double-blind trials is needed.

5.3 Glycemic Control and Metabolic Health

Annatto pigments were found to have hypoglycemic effects using dogs, rats, and human volunteers as experimental models. Thus annatto extract may have therapeutic potential for diabetes. One animal study found that annatto has a hypoglycemic property in rats with severe diabetes mellitus, which had a relatively long duration but was most pronounced two hours after drug administration. One group of diabetic animals was treated with annatto at 540 mg/kg administered via gavage. Annatto-treated diabetic animals showed significantly lower blood sugar levels than untreated diabetics.

A mouse study showed that supplementing a high-fat diet with annatto tocotrienols led to a decrease in the Firmicutes to Bacteroidetes ratio in the murine gut. The Firmicutes/Bacteroidetes ratio is reportedly a good biomarker for obesity, with data indicating that obese mice have lower Bacteroidetes and higher Firmicutes compared with lean mice. Annatto tocotrienol supplementation significantly reduced type 2 diabetes- or obesity-related hormones (such as resistin and leptin) and a proinflammatory cytokine (IL-6), according to scientists from Texas Tech University.

Annatto-extracted tocotrienols have proven benefits in preserving bone matrix. One study evaluated the effects of dietary tocotrienols on glucose homeostasis, bone properties, and liver pro-inflammatory mRNA expression in high-fat diet-induced type 2 diabetic mice. 58 male C57BL/6J mice were divided into 5 groups: low-fat diet, high-fat diet, high-fat diet + 400 mg TT/kg diet, high-fat diet + 1,600 mg TT/kg diet, and high-fat diet + 200 mg metformin/kg for 14 weeks.

In streptozotocin-induced diabetic rats, bixin supplementation attenuated inflammatory and oxidative stress markers, whereas norbixin showed limited efficacy and dose-dependent pro-oxidant effects.

Evidence strength: Primarily animal and in vitro data. Limited human volunteer data suggests hypoglycemic effects, but controlled clinical trials in human diabetic populations are absent from the published literature.

5.4 Anti-Inflammatory Activity

Treatment with bixin at 100 mg/kg/day for 18 days decreased the levels of pro-inflammatory cytokines and increased the mRNA expression of anti-inflammatory cytokines in mice with experimental autoimmune encephalomyelitis (EAE). In a separate study, male Swiss albino mice were given annatto extract (56 or 351 mg/kg) or norbixin (0.8, 7.6, 66, or 274 mg/kg) at various doses for 21 days via drinking water. A reduction of plasma globulin level was recorded in groups ingesting annatto and norbixin at 7.6, 66, and 274 mg/kg. Norbixin at 66 mg/kg also reduced the plasma urea and creatinine levels compared to the control mice.

Evidence strength: Preclinical (animal and cell-based) evidence is substantial and mechanistically well-characterized. No dedicated human clinical trials on annatto's anti-inflammatory effects have been published.

5.5 Anticancer Activity

In research into the anticancer effects of seeds of Bixa orellana, cis-bixin induced cytotoxicity in a wide variety of tumor cell lines (IC50 values from 10 to 50 μM, 24-hour exposures) and, importantly, also selectively killed freshly collected patient multiple myeloma cells and highly drug-resistant multiple myeloma cell lines. In vitro anticancer potential of the apocarotenoid bixin was demonstrated using HL60 (leukemia), B16 (melanoma), U20S (osteosarcoma), PC3 (prostate), HCT-116 (colon), MCF-7 (breast), DRO (anaplastic thyroid), and BHP-16 (papillary thyroid) cell lines.

Evidence strength: All current anticancer evidence is from in vitro cell-culture models. No human clinical trials exist. These findings are considered preliminary and hypothesis-generating only.

5.6 Antimicrobial Activity

Published research studies in animals indicate that various extracts of Bixa leaves exhibit antioxidant, broad antimicrobial (antibacterial and antifungal), anti-inflammatory, analgesic, hypoglycemic, and antidiarrheal activities. Leaf extracts were found to possess antimicrobial activity against a wide variety of bacteria and fungi, showing greatest activity against Salmonella typhi (MIC = 31.25 μg/mL) and Acinetobacter species (MIC = 31.25 μg/mL), and against the dermatophytes Trichophyton mentagrophytes and Trichophyton rubrum. Mutagenicity and carcinogenicity tests concluded that the extracts of B. orellana do not cause mutations or the appearance of cancers, even in high concentrations.

Evidence strength: In vitro and animal studies. No human clinical trials on antimicrobial applications have been published.

5.7 Skin and Photoprotection

Historically, annatto was used, among other purposes, as a sunscreen. Modern research has begun to investigate these traditional uses. The anti-inflammatory Nrf2-activating properties of bixin have been studied in the context of UV-mediated skin damage in preclinical models. The role of bixin as antioxidant, anti-inflammatory, anticancer, and skin-protecting natural product has been reviewed in the journal Fitoterapia (2023).

Evidence strength: Largely preclinical. Human data on topical annatto as a photoprotectant is absent from the peer-reviewed literature.

5.8 Safety in Human Leaf Extract Use

Few human studies have been conducted and published using Bixa leaf preparations. Many more studies have been conducted involving Bixa seed (annatto) extracts than with leaf extracts. A 6-month study in humans given 750 mg of leaf powder per day demonstrated no significant or serious adverse effects.

6. Body Systems and Health Areas of Association

• Cardiovascular system: Lipid parameter improvement, LDL oxidation resistance, reduction of CRP and inflammatory cytokines (annatto tocotrienols, bixin — clinical and animal data).
• Metabolic / endocrine system: Hypoglycemic effects; modulation of obesity-related hormones and gut microbiota composition (bixin and tocotrienols — animal and limited human data).
• Immune / inflammatory system: Inhibition of NF-κB and NLRP3 inflammasome pathways, reduction of TNF-α, IL-1β, IL-6, CRP (bixin — cell and animal data; delta-tocotrienol — clinical data).
• Oncology (preclinical only): Selective cytotoxicity against multiple tumor cell lines including multiple myeloma, melanoma, leukemia, and prostate cancer lines (in vitro only).
• Skin / integument: Historical sunscreen and wound-healing use; modern preclinical evidence for photoprotection via Nrf2 activation.
• Gastrointestinal system: Traditional use for diarrhea, gastric ulcers, and colic; limited scientific corroboration.
• Musculoskeletal system: Annatto tocotrienols associated with preservation of bone matrix in diabetic animal models.
• Metabolic regulation, showing antidiabetic, antihyperlipidemic, and anti-obesity effects; also hepatoprotective, nephroprotective, gastroprotective, and cardiovascular benefits including hypotensive and platelet anti-aggregant activities have been reported in preclinical studies.

7. Dosage Forms and Reported Study Dosages

The following dosages are reported directly from the scientific studies cited above; they are not recommendations:

• In a randomized, controlled crossover study in 16 healthy volunteers, daily supplementation with bixin or norbixin was administered at 0.05 mg/kg of body weight per day for 7 days via capsule.
• In a cardiovascular risk study, annatto tocotrienol doses of 125–750 mg/day were tested; 250 mg/day was identified as the optimum dose for lipid and inflammatory marker reduction over a 4-week period.
• In a murine encephalomyelitis model, bixin was administered at 100 mg/kg/day for 18 days.
• In a rat diabetes model, bixin (BIX) and norbixin (NBIX) were administered orally at 10 mg/kg and 100 mg/kg for 30 days in STZ-induced diabetic rats.
• In another rat diabetes model, annatto was administered at 540 mg/kg via gavage.
• A 6-month human study with Bixa orellana leaf powder used a dose of 750 mg/day.
• In a mouse model of HFD-induced type 2 diabetes, annatto-extracted tocotrienols were tested at 400 mg TT/kg diet and 1,600 mg TT/kg diet over 14 weeks.

In terms of food-additive use, EFSA set an acceptable daily intake (ADI) of 6 mg/kg body weight for bixin and 0.3 mg/kg for norbixin.

8. Safety Considerations and Interactions

Regulatory Status

The U.S. Food and Drug Administration (FDA) considers annatto extract a color additive exempt from certification. This designation means the FDA has determined that annatto is generally recognized as safe (GRAS) for use in food when employed within established limits. In the United States, the FDA permits annatto as a color additive under 21 CFR 73.30, allowing its use in certain dairy products, fats, oils, and other foods. The European Food Safety Authority (EFSA) re-evaluated the safety of annatto extracts and established an Acceptable Daily Intake (ADI) based on long-term toxicological studies. In Canada and Japan, E160b is likewise permitted within ADI limits.

EFSA Toxicological Assessment

In 2016, the EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) adopted a scientific opinion on the safety of annatto extracts (E 160b) as a food additive. The Panel concluded that the toxicological database was sufficient to derive an ADI of 6 mg bixin/kg body weight per day and an ADI of 0.3 mg norbixin/kg body weight per day. Exposure estimates for bixin were below the ADI for all population groups and for all refined exposure scenarios, including the proposed extension of use. For norbixin, exceedance was observed for the extension of use at the 95th percentile for some population groups. For norbixin, dietary exposure exceeded the ADI at the high level (95th percentile) for toddlers and children. The Panel concluded that food colour annatto E does not raise concern for genotoxicity.

In 90-day studies in rats, annatto extracts caused no mortality or major pathologies, but did show increases in liver and kidney weights, as well as changes in blood and urine parameters. High doses of one annatto extract (Annatto C) led to liver necrosis in rats. Long-term carcinogenicity studies reviewed by JECFA found no tumorigenic effects. No teratogenic or reproductive toxicity was observed.

IgE-Mediated Allergy and Anaphylaxis

Previously reported adverse reactions associated with annatto dye have included urticaria and angioedema. A documented patient developed urticaria, angioedema, and severe hypotension within 20 minutes following ingestion of milk and Fiber One cereal which contained annatto dye. Immunoblotting demonstrated patient IgE specific for one of the protein bands identified in the annatto extract. Annatto dye may contain contaminating or residual seed proteins to which IgE hypersensitivity can develop.

In rare cases, annatto dye may provoke a severe adverse reaction in individuals with an uncommon hypersensitivity, and may aggravate the symptoms of patients suffering from recurrent urticaria. A critical evaluation of the available information demonstrates that reactions to natural color additives are rare. In its long history of use, there has been only one reported case of anaphylaxis resulting from the ingestion of annatto (at the time of that publication). Studies designed to investigate the role of annatto in recurrent urticaria sufferers were limited due to the absence of double-blind challenge and placebo controls.

Differential Effects of Bixin vs. Norbixin

In a 30-day rat study, blood glucose, LDL cholesterol, and triglyceride levels were reduced in diabetic rats treated with bixin; bixin treatment prevented protein oxidation and nitric oxide overproduction and restored superoxide dismutase activity. Norbixin treatment did not change most parameters assessed, and at the highest dose (100 mg/kg), it increased LDL cholesterol and triglyceride levels and showed pro-oxidant action, including increased protein oxidation and nitric oxide levels. This finding underscores an important divergence: bixin and norbixin cannot be assumed to be pharmacologically equivalent or interchangeable, and the form used in a given preparation is toxicologically significant.

Potential Irritable Bowel Syndrome Association

A case series published in the Journal of Clinical Gastroenterology (PMID 19727005) raised the question of whether annatto may aggravate symptoms in susceptible individuals with irritable bowel syndrome (IBS), though this has not been confirmed in controlled studies.

Drug and Nutrient Interactions

Delta-tocotrienol has been shown to be more protective than alpha-tocopherol against chronic diseases such as type 2 diabetes, obesity, metabolic syndrome, fatty liver diseases, and cardiovascular diseases. It is worth noting that in the broader vitamin E literature, high-dose alpha-tocopherol supplementation may antagonize tocotrienol absorption; however, annatto tocotrienol is the only tocopherol-free source of tocotrienols, which may be advantageous in minimizing such interference. No direct drug-interaction studies specific to annatto have been published in the peer-reviewed literature reviewed here.

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