Table 1.
Dietary antioxidants and the risk of LC in smokers and non-smokers.
| Reference | Country | Research Design | Sample | Dietary Antioxidants | Findings |
|---|---|---|---|---|---|
| Männistö et al. [35] | Europe and North America | Meta-analysis of seven population-based cohort studies (follow-up duration of 7–16 years across studies) | Total subjects = 3155 LC patients Current smokers = 1915 Former smokers = 981 Non-smokers = 259 |
Carotenoids | High intake of BCX (≥160 µg/day) was associated with reduced LC risk in current smokers (RR = 0.70, 95% CI = 0.60 to 0.81) |
| Zhu et al. [36] | US, Netherlands, China, Finland and Denmark | Meta-analysis of nine population-based cohort studies (follow-up duration of 4–20 years across studies) | Total subjects = 2768 LC patients Current smokers = 1930 Former smokers = 528 Non-smokers = 310 |
Vitamin E (α-tocopherol) | Vitamin E intake (2 mg/day) was associated with reduced LC risk in current smokers (RR = 0.74, 95% CI = 0.61 to 0.89) |
| Luo et al. [40] | US, China, Netherlands, Uruguay and Canada | Meta-analysis of seven case-control and 14 population-based cohort studies | Total subjects = 2008 LC patients Current smokers = 1044 Former smokers = 702 Non-smokers = 262 |
Vitamin C | High intake of vitamin C (100 mg/day) was not associated with LC risk in current/former smokers |
| Mahabir et al. [41] | US | Case-control study | Total subjects = 2502 LC cases = 1088 (current smokers = 438; former smokers = 417; non-smokers = 238) Healthy matched controls = 1414 (current smokers = 512; former smoker = 599; non-smokers = 303) Age = ≥60 years |
Dietary tocopherols (α-, β-, γ-, and δ) | High intake of α-tocopherol (≥5.51 mg/day) was associated with reduced LC risk in current smokers (RR = 0.33, 95% CI = 0.18 to 0.62) and former smokers (RR = 0.46, 95% CI = 0.26 to 0.81) |
| Yong et al. [42] | US | Population-based cohort study (follow-up duration of 19 years) | Total subjects = 10,068 Current smokers = 3090 Former smokers = 1691 Non-smokers = 4261 Unknown smoking status = 1026 Age = 25–74 years |
Vitamins A, C and E, carotenoids | High intake of carotenoids (>2289.87 IU/day) (RR = 0.49, 95% CI = 0.29 to 0.84), vitamin E (>6.71 mg/day) (RR = 0.36, 95% CI = 0.16 to 0.83) and vitamin C (>113.05 mg/day) (RR = 0.55, 95% CI = 0.32 to 0.95) were associated with reduced LC risk in current smokers |
| Narita et al. [43] | Japan | Population-based cohort study (average 15.5 years follow-up) | Total subjects = 1896 LC patients Current smokers (male = 641, female = 28) Former smokers (male = 109, female = 0) Non-smokers (male = 109, female = 289) Light smokers (male = 37, female = 0) Heavy smokers (male = 713, female = 0) Age = 40–69 years |
Retinol, vitamin C, vitamin E and carotenoids | Retinol intake (10 mcg/day) was associated with increased LC risk in male current smokers (HR = 1.22, 95% CI = 0.99 to 1.50), and decreased LC risk in female current smokers(HR = 0.51, 95% CI = 0.18 to 1.40) α-carotene intake (>2064 µg/day) was associated with reduced LC risk in male light smokers (OR = 0.29, 95% CI = 0.09 to 0.93) No other associations with LC were observed |
| Shareck et al. [44] | Canada | Case-control study | Total subjects = 2554 LC cases = 1105 (Male current smokers = 465; former smokers = 69; non-smokers = 156, Female current smoker = 304; former smokers = 36, non-smokers = 75) Healthy matched controls = 1449 (Male current smokers = 249; former smoker = 81; non-smokers = 540, Female current smokers = 127; former smokers = 48; non-smokers = 404) Age = 35–75 years |
Vitamin C and carotenoids | High intake of BCX (>178 µg/day) (OR = 0.58, 95% CI = 0.34 to 0.89), β-carotene (>6760 µg/day) (OR = 0.49, 95% CI = 0.28 to 0.83), α-carotene (>2064 µg/day) (OR = 0.53, 95% CI = 0.31 to 0.89) and lycopene (>19,281 µg/day) (OR = 0.48, 95% CI = 0.29 to 0.79) were associated with reduced LC risk in male heavy-intensity smokers High intake of vitamin C (≥79 mg/day) (OR = 0.45, 95% CI = 0.21 to 0.95) was associated with reduced LC risk in female heavy-intensity smokers |
| Zhou et al. [45] | US | Case-control study | Total subjects = 2048 LC cases = 923 (current smokers = 378; former smokers = 489; non-smokers = 56) Healthy matched controls = 1125 (current smokers = 213; former smoker = 518; non-smokers = 394) Age = ≥18 years |
Iron and zinc | Iron intake (≥16.24 mg/d) was associated with increased LC risk in current smokers (OR = 4.03, 95% CI = 1.89 to 8.75) Zinc intake (≥12.88 mg/d) was associated with reduced LC risk in current smokers (OR = 0.41, 95% CI = 0.19 to 0.88) |
| Mahabir et al. [46] | US | Case-control study | Total subjects = 3352 LC cases = 1676 (current smokers = 747; former smokers = 693; non-smokers = 256) Healthy matched controls = 1676 (current smokers = 584; former smoker = 779; non-smokers = 313) Age = ≥60 years |
Zinc, copper and selenium | Zinc intake (>12.31 mg/d) was associated with reduced LC risk in current smokers (OR = 0.36, 95% CI = 0.22 to 0.57) Copper intake (>1.56 mg/d) was associated with reduced LC risk in current smokers (OR = 0.38, 95% CI = 0.24 to 0.60) Selenium intake was not associated with LC risk |
| Ward et al. [47] | Denmark, Greece, Italy, France, Germany, Netherlands, Norway, Spain, Sweden and the UK | Multi-centre prospective cohort study (follow-up duration of 8 years) | Total subjects = 83,348 Current smokers = 21,754 Former smokers = 20,171 Non-smokers = 41,423 Age = ≥49 years |
Iron | Total iron intake (mg/1000 kcal), but not haem and non-haem iron intake was associated with reduced LC risk in former smokers only (HR = 0.90, 95% CI = 0.83 to 0.97) |
| Mayne et al. [48] | US | Population-based cohort study (follow-up duration of 3 years) | Total subjects = 413 non-smokers Age = ≥60 years |
β-carotene and retinol | β-carotene intake was associated with reduced LC risk (OR = 0.70, 95% CI = 0.50 to 0.99) Retinol intake was not associated with LC risk |
| Wu et al. [49] | China | Population-based cohort study (follow-up duration of 12 years) | Total subjects = 72,829 female non-smokers Age = 40–70 years |
Vitamin E (α-tocopherol) | High intake of α-tocopherol (≥14 mg/day) was associated with reduced LC risk in (HR = 0.78, 95% CI = 0.60 to 0.99) |
| Liu et al. [50] | Europe, North America and Asia | Meta-analysis of six case-control and 16 population-based cohort studies | Total subjects = 15,304 LC current, former and non-smokers | Vitamin D | Vitamin E intake was associated with reduced LC risk in non-smokers only (OR = 0.76, 95% CI = 0.65 to 0.88) |
Abbreviation: LC, lung cancer; HR, hazard ratio; RR, relative risk; OR, odds ratio; CI, confidence interval.