Association between β-carotene supplementation and risk of cancer: a meta-analysis of randomized controlled trials

Abstract Context β-Carotene, which is derived from most fruits and vegetables, is the most common type of carotenes. Existing studies have demonstrated that β-carotene is associated with some positive health outcomes. However, results about the effects of supplemental β-carotene on cancer are inconsistent. Objective To determine the association between supplemental β-carotene intake and the risk of cancers. Data sources Eight databases (PubMed, Web of Science, Embase, Cochrane, China National Knowledge Infrastructure, Wangfang, China Science and Technology Journal Database, and Chinese Biomedical Literature Database) were systematically searched until September 2022. Data extraction Only reports from randomized controlled trials in which an association between supplemental β-carotene intake and the risk of cancer was found were included in the meta-analysis. Data analysis A total of 18 eligible studies based on 8 different randomized controlled trials were included in the meta-analysis, with varying sample sizes from 391 to 39 876 participants. There was no significant association between supplemental β-carotene intake and overall cancer incidence rate after synthesizing all the results (risk ratio [RR]: 1.02; 95% confidence interval [CI], 0.99–1.05). Results from subgroup analysis indicated that intake of supplemental β-carotene significantly increased the risk of lung cancer (RR: 1.19; 95%CI: 1.08–1.32), whereas no significant associations were observed for other site-specific cancers. In addition, smokers and the subgroup of participants with only low-dose β-carotene intake had a risk increment of cancer if they took supplemental β-carotene (RR: 1.16; 95%CI: 1.05–1.29). Conclusion β-Carotene supplementation has no beneficial or harmful effect on cancer incidence; moreover, it might have potentially harmful effects on lung cancer, especially for people who smoke. On the basis of the evidence from this study, supplemental intake of β-carotene is not recommended for preventing cancer, and the establishment of a tolerable upper intake level of β-carotene should be considered.