Benefits
Blood lipids in healthy adults eating annatto-enriched eggs
In an 8-week randomized trial, 105 healthy adults ate two eggs, two eggs with ground annatto, or two egg whites daily. Triglycerides, LDL and HDL cholesterol, apolipoproteins and lipoprotein particle measures did not change over time or differ between groups, so the trial shows no lipid effect, favorable or unfavorable.
Fullness ratings after eight weeks of annatto-enriched eggs
In a second report from the same 105-person egg trial, the hunger hormone ghrelin and satiety ratings did not differ between groups. Only within the annatto egg group did satisfaction and fullness ratings rise after 8 weeks. Without a between-group difference, this does not show that annatto affects appetite.
Blood oxidation markers after one high-calorie meal
In a crossover study of 12 healthy adults, a high-fat, high-carbohydrate meal eaten with a small dose of norbixin was followed by lower blood markers of inflammation and lipid oxidation over the next 1 to 2 hours than the same meal without it; bixin had a partial effect on lipid oxidation. One small study from one research group, a single meal and short-term lab markers only.
Lab-tested LDL and red blood cell oxidation over seven days
In a 16-person crossover, 7 days of annatto color extract capsules at a food-color dose left routine blood tests and most oxidation markers unchanged versus placebo, with LDL oxidation changes short of significance. A companion placebo-controlled report from the same group found red blood cells resisted lab-induced damage and lipid oxidation better after bixin or norbixin. Short-term lab markers at food-color doses, not health outcomes.
Absorption of bixin and norbixin from annatto food color
After 7 volunteers swallowed a single dose of commercial annatto color containing 16 mg of bixin, both bixin and norbixin appeared in the blood. Bixin was generally gone within 8 hours and norbixin within 24 hours, with wide differences between people, so the pigments do not appear to linger in the blood after one dose.
Lipid and oxidation markers in animal studies
In laboratory animal work, bixin at 10 to 100 mg/kg reduced artery lesions and oxidation markers in cholesterol-fed rabbits and lowered glucose and lipids in diabetic rats, while norbixin at a high dose raised lipids and acted as a pro-oxidant in rats. These doses far exceed food use, and none of this has been tested in people.
Mechanism of action
Two pigments with different solubility
Bixin is an oil-soluble apocarotenoid and norbixin is its water-dispersible form, obtained when the seed color is extracted with alkali. In a human absorption study, both appeared in plasma after one dose of bixin-based color, with norbixin persisting longer, and in rats the two had opposite effects on lipids and oxidation.
Antioxidant chemistry studied mainly in the lab
Like other carotenoids, bixin and norbixin have long chains of conjugated double bonds that can react with oxidants. Reduced lipid oxidation has been measured in rabbits and in short human studies of lab markers, but no study has shown a lasting antioxidant effect in people eating annatto.
Effects on drug-metabolizing liver enzymes in cells
In a human liver cell line, bixin raised expression of the genes for the enzymes CYP1A1 and CYP1A2, which help clear some medicines, while norbixin did not. Earlier rat work cited by the same authors found similar enzyme induction with annatto. Whether dietary amounts do this in people is untested.
Residual seed protein as an allergy trigger
Annatto color is a carotenoid extract, but in one allergy case the patient had IgE antibodies to a protein of about 50 kD found in the dye, pointing to leftover seed protein, not the pigment, as the likely cause of the reaction.
Clinical trials
Parallel randomized trial in Colombia comparing two eggs a day, two eggs with ground annatto, or two egg whites for 8 weeks, measuring blood lipids, with satiety results from the same trial published separately in Foods in 2024 (Galvis et al. 2023, Nutrients)
105 healthy adult men and women who completed the trial (109 randomized); annatto dosed at the equivalent of 1.2 mg bixin per kg body weight a day.
No significant changes over time or between groups in triglycerides, LDL or HDL cholesterol, apolipoproteins or lipoprotein subfractions. In the satiety report, ghrelin and satiety ratings did not differ between groups; only within the annatto egg group did satisfaction and fullness ratings rise (Hedges g 0.43 and 0.38). Egg whites as control could not be fully masked.
Randomized, double-blind, placebo-controlled Latin square crossover of daily capsules of bixin-rich annatto powder, norbixin powder, lycopene or placebo (0.05 mg carotenoid per kg) for 7 days each, measuring ex vivo LDL oxidation and blood markers; red cell results at the same dose and duration were published separately by the same group in Nutr Res in 2020 (Conte et al. 2019, J Nutr Metab)
16 healthy young adults (8 men, 8 women), each taking all four treatments.
No treatment changed routine blood chemistry or most oxidative stress markers. Versus placebo, the bixin-rich powder lowered the ex vivo LDL oxidation rate and nitric oxide metabolites only at p < 0.1, short of the usual significance threshold. The companion paper reports higher lab-tested red cell membrane resistance and less red cell lipid peroxidation after bixin or norbixin versus placebo (P < .05). Lab markers at food-color doses, not health outcomes.
Randomized controlled crossover in which a high-fat, high-carbohydrate meal was eaten with no carotenoid (placebo), with bixin 1.2 mg/kg, or with norbixin 0.06 mg/kg, with blood sampled over 4 hours (Roehrs et al. 2017, Food Res Int)
12 healthy adults (6 men, 6 women).
According to the abstract, the norbixin meal lowered postprandial IL-1, IL-6, TNF-alpha and lipid oxidation at 60 to 120 minutes, while bixin only partly prevented the rise in lipid oxidation; neither changed routine blood chemistry. A single-meal study of short-term blood markers from one research group; longer use was not tested.
Uncontrolled absorption study after one dose of 1 mL commercial annatto food color (16 mg cis-bixin in soybean oil) (Levy et al. 1997, Analyst)
7 volunteers.
Both bixin and norbixin were detected in plasma, with norbixin at higher levels than bixin over 2 to 8 hours. Bixin was generally cleared by 8 hours and norbixin by 24 hours, with considerable variation between individuals. No control group and no health outcomes.
60-day study in rabbits on a 0.5% cholesterol diet given bixin at 10, 30 or 100 mg/kg, compared with untreated cholesterol-fed rabbits and a statin group (Somacal et al. 2015, Mol Cell Biochem)
Rabbits; no people.
Bixin reduced aortic lesion extent by up to 55% and was accompanied by 60% lower lipid peroxidation, 37% lower non-HDL cholesterol, 41% lower triglycerides and higher HDL cholesterol versus untreated cholesterol-fed rabbits. Doses were far above food-color intake, and the result has not been tested in people.
30-day study in chemically induced diabetic rats given bixin or norbixin at 10 or 100 mg/kg, with metformin and insulin comparison groups (Roehrs et al. 2014, Int J Endocrinol)
Rats; no people.
Bixin lowered blood glucose, LDL cholesterol and triglycerides and reduced oxidation markers. Norbixin changed most measures little, and at 100 mg/kg it raised LDL cholesterol and triglycerides and acted as a pro-oxidant. The two main annatto pigments behaved differently, so results for one cannot be assumed for the other.