News

Total Carotenoids Curb
Lung Cancer Risk In Smokers

Higher pre-diagnostic serum levels of total carotenoids and beta-cryptoxanthin have been found to be linked with lower smoking-related lung cancer risk in middle-aged and older Chinese men. At the same time, a low level of serum retinol (with a threshold effect) is associated with increased risk of lung cancer risk in this population.

Higher blood levels of beta-carotene have previously been shown to be linked with reduced lung cancer risk. However, large intervention trials have failed to show reduced incidence of this disease after prolonged high-dose beta-carotene supplementation. Until now, little has been known about the link between lung cancer risk and pre-diagnostic serum levels of carotenoids, retinal and tocopherols, especially in non-Western populations. This large prospective study of diet and cancer was done in Shanghai, China between January 1986 and September 1989. Dr J. M. Yuan and colleagues from the University of Southern California, Los Angeles, California, United States and the Shanghai Cancer Institute, Shanghai did the research.

Study participants were 18,244 men aged 45 years to 64 years who, in in-person interviews, provided information on tobacco smoking and other lifestyle factors. All also provided a baseline serum sample. In the first 12 years of follow-up, researchers identified 209 lung cancer cases, excluding those diagnosed within two years of enrolment. For each cancer case, three cancer-free controls were randomly selected from the cohort and matched to the index case by age (within two years), month and year of blood sample collection and neighbourhood of residence.

In 209 cancer cases and 622 matched controls, researchers determined serum concentrations of retinal, alpha- and gamma-tocopherols and specific carotenoids, including alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene and lutein-zeaxanthin. This was done via high-performance liquid chromatography.

A high pre-diagnostic serum level of beta-cryptoxanthin was significantly related to reduced risk of lung cancer.

Increased serum levels of other specific carotenoids, including alpha-carotene, beta-carotene, lycopene and lutein-zeaxanthin were also related to reduced lung cancer risk although the inverse associations were no longer statistically significant after smoking was taken into account.

A statistically significant 37 percent reduction in risk of lung cancer was noted in smokers with above versus below median level of total carotenoids.

Serum retinal levels showed a threshold effect on risk of the disease. There were no associations between pre-diagnostic serum levels of alpha- and gamma-tocopherols and lung cancer.

Source: Cancer Epidemiol Biomarkers Prev 2001 Jul;10(7):767-773. "Prediagnostic Levels of Serum ß-Cryptoxanthin and Retinol Predict Smoking-related Lung Cancer Risk in Shanghai, China 1"