What is the relationship between beta-carotene (a precursor to Vitamin A) supplementation and lung cancer risk in smokers, and Vitamin A intake and lung cancer risk in smokers?

From the Guidelines

Beta carotene supplements are not recommended for smokers due to evidence suggesting they may increase lung cancer risk. Studies have shown that high-dose beta carotene supplementation in smokers is associated with a higher incidence of lung cancer compared to placebo, with a relative risk of 1.28 (P = 0.02) for lung cancer in the treatment arm compared with the placebo arm 1. Similarly, high-dose vitamin A (retinol) supplements should also be avoided by smokers. The mechanism behind this adverse effect likely involves the interaction between tobacco smoke carcinogens and these nutrients, potentially promoting rather than preventing cellular damage in lung tissue.

Key Points to Consider

• 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 beta carotene supplementation provides no benefit in the prevention of cancer or cardiovascular disease in middle-aged and older adults 1.
• Instead of supplements, smokers should focus on obtaining these nutrients through a balanced diet rich in fruits and vegetables, which provide natural amounts of beta carotene and vitamin A along with other beneficial compounds.
• The most effective way for smokers to reduce lung cancer risk remains smoking cessation.
• If nutritional support is needed, smokers should consult healthcare providers for personalized advice that considers their specific health status and avoids potentially harmful supplementation 1.

Recommendations for Smokers

• Avoid high-dose beta carotene and vitamin A supplements
• Focus on a balanced diet rich in fruits and vegetables
• Consider consulting a healthcare provider for personalized nutritional advice
• Prioritize smoking cessation as the most effective way to reduce lung cancer risk

From the Research

Relationship Between Beta-Carotene Supplementation and Lung Cancer Risk in Smokers

• Beta-carotene supplementation has been associated with an increased risk of lung cancer in smokers, with a relative risk (RR) of 1.16 (95% CI = 1.06-1.26) 2.
• A randomized, double-blind, placebo-controlled trial found that daily supplementation with beta-carotene (20 mg per day) was associated with a higher incidence of lung cancer among male smokers, with a change in incidence of 18% (95% confidence interval, 3 to 36 percent) 3.
• The increased risk of lung cancer associated with beta-carotene supplementation was more noticeable among smokers and asbestos workers (RR = 1.21,95% CI = 1.08-1.35) 2.

Relationship Between Vitamin A Intake and Lung Cancer Risk in Smokers

• High intake of fruits and vegetables containing carotenoids has been associated with a reduced risk of lung cancer, but little relation has been found between intake of preformed vitamin A and this disease 4.
• Prediagnostic levels of beta-carotene in blood have been inversely related with risk of lung cancer, suggesting that dietary carotenoids may reduce the risk of lung cancer 4.
• The relationship between diet and lung cancer is modest compared with the deleterious effect of cigarette smoking, and the data are also compatible with the possibility that some other factor in these foods is responsible for the lower risk 4.

Safety Concerns and Recommendations

• Intervention trials with large doses of beta-carotene found an adverse effect on the incidence of lung cancer in smokers and workers exposed to asbestos, and current dietary recommendations of diets high in fruits and vegetables are advised 5.
• The Joint FAO/WHO Expert Committee on Food Additives withdrew Acceptable Daily Intake values for β-carotene due to the increased incidence of lung cancer and total mortality among heavy smokers taking β-carotene supplements 6.
• Consumption of up to 50 mg/day β-carotene does not present safety concerns for the non-smoking general population, but heavy smokers consuming less than 15 mg β-carotene/day are not expected to be at an increased risk of lung cancer 6.