From the Guidelines
Beta-carotene supplements have been associated with an increased risk of lung cancer in people who smoke and should be avoided by this population. The evidence from large clinical trials, such as the ATBC study and the CARET trial 1, demonstrates a higher incidence of lung cancer in smokers taking beta-carotene supplements compared to those not taking the supplement. The mechanism behind this adverse effect is thought to be related to the interaction between beta-carotene and tobacco smoke in the lungs, potentially promoting cellular damage in this specific population.
Key Points
- The increased risk of lung cancer associated with beta-carotene supplementation is particularly significant in current smokers, with a relative risk of 1.40 (95% CI, 1.07-1.87) in the CARET trial 1.
- Beta-carotene from food sources is generally considered safe, but the concentrated amounts found in supplements pose a risk to smokers.
- Non-smokers do not appear to face the same increased risk from beta-carotene supplementation.
- The USPSTF recommends against supplementation with beta-carotene, either alone or in combination, for the prevention of cancer or cardiovascular disease, citing good evidence that it provides no benefit and may cause harm in some groups 1.
Recommendations
- Smokers and those with a history of smoking should avoid taking beta-carotene supplements.
- Instead, they should focus on getting their nutrients from a balanced diet rich in fruits and vegetables.
- Patients should be reminded that taking vitamins does not replace the need to eat a healthy diet, and they should receive information about the benefits of a diet high in fruits and vegetables.
From the Research
Supplement Associated with Increased Risk of Lung Cancer
- Beta-carotene supplementation has been linked to an increased risk of lung cancer in people who smoke, as shown in several studies 2, 3, 4, 5, 6.
Key Findings
- A study published in the American Journal of Epidemiology found that longer duration of use of individual beta-carotene supplements was associated with a statistically significantly elevated risk of total lung cancer and histologic cell types 2.
- A systematic review and meta-analysis published in Nutrients found that beta-carotene supplementation was associated with an increased risk of lung cancer, particularly among smokers and asbestos workers 3.
- A meta-analysis published in Cancer found that beta-carotene supplementation was significantly associated with an increased risk of lung cancer among current smokers, but not among former smokers 4.
Mechanism of Interaction
- The mechanism of interaction between beta-carotene and tobacco smoke is not fully understood, but it is thought to involve alterations of retinoid metabolism and signaling pathways, as well as interaction with CYP enzymes and pro-oxidation/DNA oxidation 5.
Recommendations
- Based on the available evidence, it is recommended that smokers avoid beta-carotene supplementation, as it may increase the risk of lung cancer regardless of the tar or nicotine content of cigarettes smoked 6.