Is beta-carotene safe for smokers?
Most of the concern regarding smoking and beta-carotene comes from the CARET and PHS studies published in the late 1990s. It is important to understand that one set of study participants averaged 50 pack years of cigarettes (i.e. 4 packs a day for 12.5 years or 2 packs per day for 25 years). Another set of participants were already diagnosed with lung damage (due to chronic asbestos exposure). Given these conditions, both groups already had a high risk of lung cancer. In addition, both groups took very high doses of both beta-carotene and vitamin A.
Subsequent studies have been done using more moderate dosages of beta-carotene (similar to the dosage in the USANA CellSentials) alongside vitamin C and vitamin E. These results showed that when other antioxidants are added to beta-carotene supplementation, the results are quite different. In fact, when used in combination the antioxidants appeared to be protective against cancer progression – even in lung tissue exposed to smoke. These subsequent results support the common sense message USANA has always espoused: that supplements should be balanced, complete, and taken with a healthy diet.
For your convenience, we have included an abstract from a published paper on beta-carotene, carotenoids, and lung cancer incidence.
Cancer Epidemiol Biomarkers Prev. 2004 Jan;13(1):40-8
Dietary carotenoids and risk of lung cancer in a pooled analysis of seven cohort studies
Mannisto S, Smith-Warner SA, Spiegelman D, Albanes D, Anderson K, van den Brandt PA, Cerhan JR, Colditz G, Feskanich D, Freudenheim JL, Giovannucci E, Goldbohm RA, Graham S, Miller AB, Rohan TE, Virtamo J, Willett WC, Hunter DJ.
Harvard School of Public Health, Department of Nutrition, Boston, Massachusetts, USA.
Intervention trials with supplemental beta-carotene have observed either no effect or a harmful effect on lung cancer risk. Because food composition databases for specific carotenoids have only become available recently, epidemiological evidence relating usual dietary levels of these carotenoids with lung cancer risk is limited. We analyzed the association between lung cancer risk and intakes of specific carotenoids using the primary data from seven cohort studies in North America and Europe. Carotenoid intakes were estimated from dietary questionnaires administered at baseline in each study. We calculated study-specific multivariate relative risks (RRs) and combined these using a random-effects model. The multivariate models included smoking history and other potential risk factors. During follow-up of up to 7-16 years across studies, 3,155 incident lung cancer cases were diagnosed among 399,765 participants. beta-Carotene intake was not associated with lung cancer risk (pooled multivariate RR = 0.98; 95% confidence interval, 0.87-1.11; highest versus lowest quintile). The RRs for alpha-carotene, lutein/zeaxanthin, and lycopene were also close to unity. beta-Cryptoxanthin intake was inversely associated with lung cancer risk (RR = 0.76; 95% confidence interval, 0.67-0.86; highest versus lowest quintile). These results did not change after adjustment for intakes of vitamin C (with or without supplements), folate (with or without supplements), and other carotenoids and multivitamin use. The associations generally were similar among never, past, or current smokers and by histological type. Although smoking is the strongest risk factor for lung cancer, greater intake of foods high in beta-cryptoxanthin, such as citrus fruit, may modestly lower the risk.