Beta‐carotene in multivitamins and the possible risk of lung cancer among smokers versus former smokers

Abstract

BACKGROUNDSome studies have suggested that beta‐carotene supplementation may increase the risk of lung cancer, particularly among smokers or former smokers. Beta‐carotene, a provitamin A, is available in multivitamins. In the current study, the authors investigated the risk of lung cancer associated with beta‐carotene in smokers or former smokers and surveyed the beta‐carotene content in national brand multivitamins.METHODSThe authors systemically reviewed the published literature using a search of the MEDLINE database and performed a meta‐analysis of large randomized trials that reported on the effect of beta‐carotene supplementation on the incidence of lung cancer among smokers or former smokers. A sample of multivitamins was evaluated for their beta‐carotene content and the suggested daily dosage.RESULTSFour studies contributing 109,394 subjects were available for analysis. The average daily beta‐carotene dosage in these trials ranged from 20 to 30 mg daily. Among current smokers, beta‐carotene supplementation was found to be significantly associated with an increased risk of lung cancer (odds ratio [OR], 1.24; 95% confidence interval [95% CI], 1.10–1.39). Among former smokers, there was no significant increase noted (OR, 1.10; 95% CI, 0.84–1.45). In a sample of 47 common multivitamins, beta‐carotene was present in 70% of the identified formulas. The median dosage of beta‐carotene was 0.3 mg (range, 0–17.2 mg) daily. The beta‐carotene content was found to be significantly higher among multivitamins sold to improve visual health than among other multivitamins, with a median daily dosage of 3 mg (range, 0–24 mg).CONCLUSIONSHigh‐dose beta‐carotene supplementation appears to increase the risk of lung cancer among current smokers. Although beta‐carotene was prevalent in multivitamins, high‐dose beta‐carotene was observed among multivitamin formulas sold to promote visual health. Cancer 2008. © 2008 American Cancer Society.

Adverse effects of antioxidative vitamins

“…In view of the data presented above that β-carotene does not cause any significant health threats, the effect of supplementation with this substance (20 mg/d) in smokers was surprising, with 18%-increase in lung cancer incidence and the increased mortality caused by this compound [51][52][53][54]. Similar results were noted for the supplementation of patients occupationally exposed to asbestos [39,55].…”

“…In turn, β-apo-carotenals, formed from peroxide radical-induced asymmetric breakdown of β-carotene, produce specific isoforms of cytochrome P-450 which convert procarcinogens present in the cigarette smoke into ultimate carcinogens, thereby enhancing progression of lung neoplasms in smokers. Those effects are eliminated by the parallel administration of vitamin E, which prevents β-apo-carotenal generation [43,54]. Selective supplementation with β-carotene also affects the content of various other antioxidants in the organism.…”

Hen egg carotenoids (lutein and zeaxanthin) and nutritional impacts on human health: a review

“…In short, lutein and zeaxanthin are considered as appropriate supplement in controlling AMD (AOA, 2012;Ma et al, 2012b), duly backed by the AREDS2 (AgeRelated Eye Disease Study 2) (Chew et al, 2014). This study evaluated the significance of replacing β-carotene with lutein/zeaxanthin in the AREDS formulation (Chew et al, 2014) because of the demonstrated risk for lung cancer from β-carotene in smokers and former smokers (Tanvetyanon & Bepler, 2008). Overall, consensual evidence suggests that lutein/zeaxanthin could be more appropriate supplement than β-carotene in curing age-related eye diseases (Chew et al, 2014).…”

The Concept of Cyclical Nutritional Therapy for Hair Growth which can be Applied for Wellness

“…Synthetic retinoids can impair liver functions [5]. Vitamin A has been found to damage bone and increase incidence of hip fractures at just marginally higher doses without signs of hypervitaminosis [35][36][37]. Excess β-carotene which is an effective antioxidant at low partial pressure of oxygen (pO 2 ) as in peripheral tissues becomes pro oxidant at high pO 2 as in lungs even leading to DNA (Deoxyribonucleic acid) damage [38][39][40][41].…”