Beta-carotene is a natural pigment present in many yellow, orange, and dark green fruits and vegetables. The body converts it into vitamin A, which helps prevent vitamin A deficiency and acts as an antioxidant. While beta-carotene from food sources is safe and beneficial, taking high-dose supplements may be harmful, especially for smokers. Consuming large amounts through food can sometimes cause a harmless yellow-orange tint to the skin, known as carotenodermia.
Beta-carotene was first isolated from carrots in 1831 by Heinrich Wackenroder. Its chemical formula was identified in 1907, and its complete structure was determined by Paul Karrer between 1930 and 1931—a discovery that earned him a Nobel Prize.
BRAND NAMES
Lumitene: A prescription beta-carotene product commonly used to manage specific medical conditions.
A-Caro-25: Another brand name for a prescription formulation of beta-carotene.
MECHANISM OF ACTION
Beta-carotene functions as an antioxidant with strong activity against reactive oxygen species, particularly singlet oxygen. It serves as a scavenger for lipophilic radicals within cell membranes across all cellular compartments and also influences the oxidative modification of LDL. Its antioxidant properties stem from its long chains of conjugated double bonds, which enable beta-carotene to neutralize oxygen free radicals and dissipate their energy. This process helps prevent lipid peroxidation by inhibiting free radical activity.
PHARMACOKINETICS:
Absorption
Beta-carotene absorption varies widely (about 5%–65%) and depends on its release from plant tissues and conversion into a form the body can use. It must be micellarized in the intestine, absorbed by intestinal cells, and converted to vitamin A when needed. Chewing, chopping, and cooking foods can improve its absorption.
Distribution
Beta-carotene, found in colorful fruits and leafy greens, is absorbed with dietary fats and carried in the blood by lipoproteins like LDL and HDL. It is distributed to tissues, especially the liver and lungs, where it is converted into vitamin A.
Metabolism
The metabolism of beta-carotene involves several stages, from absorption in the gut to its conversion into vitamin A (retinol), distribution throughout the body, and eventual storage or excretion. This process is highly regulated and influenced by dietary fat, genetic factors, and the body's vitamin A needs.
Excretion
The excretion of beta-carotene and its metabolites occurs through the feces and urine. The primary route of excretion for unabsorbed beta-carotene is the feces, while the water-soluble metabolites are eliminated via bile and urine.
PHARMACODYNAMICS
Oral intake of beta-carotene raises its serum levels by 60%, but does not affect its concentration in the heart, liver, or kidneys. In vitro studies on liver cells (hepatocytes) have demonstrated that beta-carotene reduces oxidative stress, boosts antioxidant activity, and lowers cell apoptosis.
ADMINISTRATION
Beta-carotene is taken orally through food or supplements and is best absorbed when consumed with dietary fat. Dosage depends on age and purpose, with typical daily recommendations of 6 to 15 mg for adults and 3 to 6 mg for children. Higher doses may be used therapeutically, such as for sun sensitivity in patients with erythropoietic protoporphyria. For most people, obtaining beta-carotene from fruits and vegetables is preferred over supplements.
DOSAGE AND STRENGTH
The dosage of beta-carotene varies based on the individual and medical condition, so it’s important to follow your doctor’s instructions or the label directions. For general dietary supplementation, adults and teens typically take 6 to 15 mg daily, while children take 3 to 6 mg. Higher doses are used to treat sun sensitivity in conditions like erythropoietic protoporphyria and polymorphous light eruption, with adults sometimes taking up to 300 mg daily. If your vitamin A levels are high, your body will convert less beta-carotene into vitamin A.
DRUG INTERACTIONS
Beta-carotene supplements interact with several medications, including cholesterol-lowering drugs, weight-loss medications, and alcohol, which can interfere with its absorption or effectiveness. It is important to note that most of these interactions concern beta-carotene supplements, not the beta-carotene found naturally in foods.
FOOD INTERACTIONS
Beta-carotene supplements interact with several medications, including cholesterol-lowering drugs, weight-loss medications, and alcohol, which can interfere with its absorption or effectiveness. It is important to note that most of these interactions concern beta-carotene supplements, not the beta-carotene found naturally in foods.
CONTRAINDICATIONS
High-dose beta-carotene supplements are contraindicated for people who smoke, have a history of smoking, or have been exposed to asbestos. For these populations, high supplemental doses of beta-carotene can increase the risk of lung cancer and other negative health outcomes, including a higher risk of death from cardiovascular disease.
SIDE EFFECTS
Diarrhea
Lightheadedness
Joint discomfort
Unexpected bleeding or bruising
OVER DOSE
An overdose of beta-carotene from food is usually harmless and may cause a temporary yellow-orange discoloration of the skin called carotenemia. However, taking high-dose beta-carotene supplements—particularly for smokers—can raise the risk of certain cancers and may be associated with a higher risk of death from all causes. In rare cases, very high doses can cause side effects such as dizziness or joint pain, though these are not related to vitamin A toxicity.
TOXICITY
Beta-carotene is generally not toxic even in large amounts. However, taking high doses for an extended period can cause carotenemia, a condition that turns the skin yellow-orange. Excessive beta-carotene can be problematic for certain individuals.
