Role of Beta-Carotene in Lung Cancer Primary Chemoprevention: A Systematic Review with Meta-Analysis and Meta-Regression

Our plain-English summary of Role of Beta-Carotene in Lung Cancer Primary Chemoprevention: A Systematic Review with Meta-Analysis and Meta-Regression, by J. Kordiak, F. Bielec, S. Jabłoński, et al (Nutrients, 2022).

The study

• Authors: J. Kordiak, F. Bielec, S. Jabłoński, D. Pastuszak-Lewandoska
• Journal: Nutrients
• Published: 2022;14(7)
• Type of article: Meta-analysis, Systematic review
• Cited by: 53 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Lung cancer is one of the most common neoplasms globally, with about 2.2 million new cases and 1.8 million deaths annually. Although the most important factor in reducing lung cancer risk is lifestyle change, most patients favour the use of supplements, for example, rather than quitting smoking or following a healthy diet. To better understand the efficacy of such interventions, a systematic review was performed of data from randomized controlled trials concerning the influence of beta-carotene supplementation on lung cancer risk in subjects with no lung cancer before the intervention. The search corpus comprised a number of databases and eight studies involving 167,141 participants, published by November 2021. The findings indicate that beta-carotene supplementation was associated with an increased risk of lung cancer (RR = 1.16, 95% CI = 1.06-1.26). This effect was even more noticeable among smokers and asbestos workers (RR = 1.21, 95% CI = 1.08-1.35) and non-medics (RR = 1.18, 95% CI = 1.07-1.29). A meta-regression found no relationship between the beta-carotene supplementation dose and the size of the negative effect associated with lung cancer risk. Our findings indicate that beta-carotene supplementation has no effect on lung cancer risk. Moreover, when used as the primary chemoprevention, beta-carotene may, in fact, increase the risk of lung cancer.

In plain English

This systematic review and meta-analysis pooled randomized controlled trials of beta-carotene supplements for preventing lung cancer. It included eight trials with 167,141 participants in the USA, Finland, the UK and China, published by November 2021. One trial group (CARET) was 4,060 male asbestos workers in the USA, randomly assigned to placebo or to 30 mg beta-carotene daily plus retinol. Every trial also tested other substances, though some participants in some trials took beta-carotene without them. Overall, people given beta-carotene had a higher relative risk (RR) of lung cancer than those given placebo: 1.16 (95% CI 1.06–1.26). For smokers and asbestos workers combined, the RR was 1.21 (95% CI 1.08–1.35). The asbestos-worker group on its own had an RR of 1.40 (95% CI 0.95–2.07), a range that includes no difference. No statistically significant link was found between dose and risk. The authors concluded that beta-carotene has a negative effect on lung cancer risk in smokers and asbestos workers. They noted that because other antioxidants were also given, the effect may not come from beta-carotene alone.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Systematic review with meta-analysis and meta-regression of randomized controlled trials
• Who was studied: Eight randomized controlled trials, reported in seven publications, with 167,141 adult participants in total. The trials were run in the USA, Finland, the UK and China. One CARET trial group was 4,060 asbestos workers in the USA, all men (39% current and 58% former smokers). The search ran up to November 2021.
• Exposure: Beta-carotene supplements: 15 to 30 mg daily, or 50 mg on alternate days, compared with placebo. Every trial's design also included other substances (alpha-tocopherol, aspirin, vitamins E and C, retinol, or selenium). In some trials (ATBC, WHS, WACS), some participants received beta-carotene with no added substance. In CARET, asbestos workers assigned to the intervention took 30 mg beta-carotene daily plus 25,000 IU retinol. Asbestos was not the exposure studied; asbestos workers were one of the populations.
• Main results:
  • All trials combined: people given beta-carotene had a higher risk of lung cancer than those given placebo, RR 1.16 (95% CI 1.06 to 1.26), p = 0.001
  • Smokers and asbestos workers subgroup (ATBC smokers, CARET heavy smokers and CARET asbestos workers together): RR 1.21 (95% CI 1.08 to 1.35)
  • CARET asbestos-worker group alone (4,060 men): RR 1.40 (95% CI 0.95 to 2.07), as listed in the review's table of included studies. This interval includes 1 (no difference).
  • Non-medical participants: RR 1.18 (95% CI 1.07 to 1.29)
  • Statistically significantly higher risk was found in the US and European populations, men, smokers, and non-health professionals. No statistically significant effects were seen in the other subgroups.
  • Meta-regression found no statistically significant relationship between beta-carotene dose and lung cancer risk. The authors noted a general trend toward higher risk with higher daily dose.
• The authors' conclusion: The authors concluded that beta-carotene supplementation has a negative effect on lung cancer risk in smokers and asbestos workers. They called for further trials, including in non-smokers and people not exposed to dust such as asbestos.
• Limitations the authors state:
  • Not all trials had complete data that could be extracted; for example, smoking status was missing for two trials.
  • In all trials beta-carotene was given with other antioxidants, so the effect may not be due to beta-carotene specifically.
  • The only Asian trial studied a nutrient-deficient population, so its result may reflect correction of dietary deficiency.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Systematic Review, Meta-Analysis, Neoplasm.

Related studies

• Chemoprevention of cancer: lessons to be learned from beta-carotene trials — H. Vainio (2000)
• Chemoprevention or antichemoprevention? A salutary warning From the beta-carotene experience — M. Paolini, S.Z. Abdel-Rahman, et al. (2001)
• Beta-carotene and the application of transcriptomics in risk-benefit evaluation of natural dietary components — J. Keijer, A. Bunschoten, et al. (2005)
• The enigma of beta-carotene in carcinogenesis: what can be learned from animal studies — R.M. Russell (2004)
• Beta-carotene supplementation and cancer risk: a systematic review and metaanalysis of randomized controlled trials — N. Druesne-Pecollo, P. Latino-Martel, et al. (2010)
• Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial — G.S. Omenn, G.E. Goodman, et al. (1996)

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