β-Carotene (beta-carotene) is an organic, strongly colored red-orange pigment abundant in fungi,[7] plants, and fruits.

[8][14][15] As part of the digestive process, food-sourced carotenoids must be separated from plant cells and incorporated into lipid-containing micelles to be bioaccessible to intestinal enterocytes.

[16] At the enterocyte cell wall, β-carotene is taken up by the membrane transporter protein scavenger receptor class B, type 1 (SCARB1).

[16] Once taken up by peripheral tissue cells, the major usage of absorbed β-carotene is as a precursor to retinal via symmetric cleavage by the enzyme beta-carotene 15,15'-dioxygenase, which is encoded by the BCO1 gene.

[17][18] For counting dietary vitamin A intake, β-carotene may be converted either using the newer retinol activity equivalents (RAE) or the older international unit (IU).

[8] The most common side effect of excessive β-carotene consumption is carotenodermia, a physically harmless condition that presents as a conspicuous orange skin tint arising from deposition of the carotenoid in the outermost layer of the epidermis.

[8][9][16][24] Carotenoderma, also referred to as carotenemia, is a benign and reversible medical condition where an excess of dietary carotenoids results in orange discoloration of the outermost skin layer.

The discoloration extends to palms and soles of feet, but not to the white of the eye, which helps distinguish the condition from jaundice.

[16][26] At the enterocyte cell wall, β-carotene is taken up by the membrane transporter protein scavenger receptor class B, type 1 (SCARB1).

[32] Additional research is required to understand the link between the increased risk of cancer and all-cause mortality following β-carotene supplementation.

Additionally, supplemental, high-dose β-carotene may increase the risk of prostate cancer, intracerebral hemorrhage, and cardiovascular and total mortality irrespective of smoking status.

[35] However, a 2018 meta-analysis mostly of prospective cohort studies found that both dietary and circulating beta-carotene are associated with a lower risk of all-cause mortality.

[36] Age-related macular degeneration (AMD) represents the leading cause of irreversible blindness in elderly people.

AMD is an oxidative stress, retinal disease that affects the macula, causing progressive loss of central vision.

These studies found no evidence of any protective effects afforded by β-carotene supplementation on preventing and slowing age-related cataract.

[43] A second meta-analysis compiled data from studies that measured diet-derived serum beta-carotene and reported a not statistically significant 10% decrease in cataract risk.

[44] High doses of β-carotene (up to 180 mg per day) may be used as a treatment for erythropoietic protoporphyria, a rare inherited disorder of sunlight sensitivity, without toxic effects.