Erythropoietic protoporphyria is a rare inherited genetic disorder of porphyrin-heme metabolism which has skin and systemic manifestations, including photosensitivity (painful skin sensitivity to sunlight), as well as gallstones and liver dysfunction. It is usually recognized during childhood. The over-the-counter synthetic beta-carotene product Lumitene is FDA approved for photoprotection in this disease. Antihistamines may also be used to reduce symptoms.

Although consumption of provitamin A carotenoids (alpha-carotene, beta-carotene, and beta-cryptoxanthin) can prevent vitamin A deficiency, no overt deficiency symptoms have been identified in people consuming low-carotenoid diets if they consume adequate vitamin A. After reviewing the published scientific research, the Food and Nutrition Board of the Institute of Medicine (IOM) concluded that the existing evidence in 2000 was insufficient to establish a recommended dietary allowance (RDA) or adequate intake (AI) for carotenoids.

Study results of beta-carotene supplementation for cataract prevention are conflicting. Further well-designed clinical trials are needed before a conclusion can be drawn.

Observational research suggests that greater dietary intake of beta-carotene may lower the incidence of adverse effects in children undergoing chemotherapy for lymphoblastic leukemia. However, in theory high-dose antioxidants may interfere with the activity of some chemotherapy drugs or radiation therapy. Therefore, individuals undergoing cancer treatment should speak with their oncologist if they are taking or considering the use of high dose antioxidants. Additional evidence is needed in this area before a clear conclusion can be drawn.

The prevalence of bronchitis and shortness of breath in male smokers with chronic obstructive pulmonary disorder (COPD) seems to be lower in those patients who consume a diet containing high amounts of beta-carotene. However, beta-carotene supplements have not been proven to benefit COPD and may actually increase cancer rates in smokers.

Individuals with cystic fibrosis may be deficient in beta-carotene and vitamin E, and it has been suggested that they may be more susceptible to oxidative damage. Theoretically, these patients may benefit from beta-carotene supplementation. Further research is needed before a conclusion can be drawn.

Based on preliminary evidence, taking a mixture of beta-carotene isomers orally may prevent exercise-induced asthma. However, because synthetic beta-carotene has not been well tested for this indication, the difference between the activities of the two supplements cannot be deduced. Further research is needed before a recommendation can be made.

Preliminary research of beta-carotene for immune system maintenance or stimulation shows mixed results. Further research is needed before a conclusion can be drawn.

Taking beta-carotene and other antioxidants has been proposed to help prevent or delay progression of age-related macular degeneration. However, other dietary carotenoids such as lycopene, lutein, and zeaxanthin may provide greater protection from radiation and oxidative damage in the retina than beta-carotene. Further research is needed before a conclusion can be drawn.

Taking beta-carotene orally seems to induce remission in patients with oral leukoplakia. Further research is needed to confirm these results.

Beta-carotene supplementation does not appear to prevent osteoarthritis, but it might slow progression of the disease. Well-designed clinical trials are needed before a conclusion can be drawn.

Beta-carotene has been used for PLE. Additional study is needed in this area.

All-trans beta-carotene (synthetic beta-carotene) taken weekly before, during, and after pregnancy may reduce pregnancy-related mortality, night blindness, post partum diarrhea and fever. A regular intake of a micronutrient supplement at a nutritional dose may be sufficient to improve micronutrient status of apparently healthy pregnant women and could prevent low birth weight of newborn. However, further research is necessary to consolidate the evidence in this area before a clear recommendation can be made.

A combination of antioxidants may help protect the skin against irradiation. Long-term supplementation with beta-carotene may reduce UV-induced erythema, and appears to modestly reduce the risk of sunburn in individuals who are sensitive to sun exposure. However, beta-carotene is unlikely to have much effect on sunburn risk in most people.

Long-term supplementation with alpha-tocopherol or beta-carotene has been shown not to have a protective or preventive effect in male smokers with large AAAs.

Intake of dietary or supplemental beta-carotene has been shown not to have any effect on Alzheimer's disease risk.

There is some concern that when antioxidant vitamins, including beta-carotene, are used together they might have harmful effects in patients after angioplasty. Additional research is needed to determine the effect of beta-carotene specifically. Supplements containing these vitamins should be avoided immediately before and following angioplasty without the recommendation of a qualified healthcare professional.

Beta-carotene has been shown not to reduce the development of new moles in patients with numerous atypical moles.

While diets high in fruits and vegetables rich in beta-carotene have been shown to potentially reduce the incidence of certain cancers, results from randomized controlled trials with oral supplements do not support this claim.There is some concern that beta-carotene metabolites with pharmacological activity can accumulate and potentially have cancer causing (carcinogenic) effects. A higher, statistically significant incidence of lung cancer in male smokers who took beta-carotene supplements has been discovered. Beta-carotene/vitamin A supplements may have an adverse effect on the incidence of lung cancer and on the risk of death in smokers and asbestos exposed people or in those who ingest significant amounts of alcohol. In addition, high-dose antioxidants theoretically may interfere with the activity of some chemotherapy drugs or radiation therapy. Therefore, individuals undergoing cancer treatment should speak with their oncologist if they are taking or considering the use of high dose antioxidants.Beta-carotene in the amounts normally found in food does not appear to have this adverse effect.

Although several studies suggest that diets high in fruits and vegetables containing beta-carotene appear to reduce the risk of cardiovascular disease, most randomized controlled trials with oral supplements of beta-carotene have not supported these claims.A Science Advisory from the American Heart Association states that the evidence does not justify use of antioxidants such as beta-carotene for reducing the risk of cardiovascular disease.

Infection with Helicobacter pylori bacteria in the gut can lead to gastric ulcers. Dietary supplementation with beta-carotene has not been found to be effective for this indication.

Patients given beta-carotene supplements show no reduction in relative mortality rates from all causes based on most available data.

Study results conclude that peri-operative supplementation with antioxidant micronutrients has limited effects on strength and physical function following major elective surgery.

Taking all-trans beta-carotene (synthetic beta-carotene) orally has been reported to have no effect on the overall incidence of stroke in male smokers. Additionally, there is some evidence that beta-carotene actually increases the risk of intracerebral hemorrhage by 62% in patients who also drink alcohol.