Table 1.
Characteristics of eligible studies on dietary vitamin C intake and prostate cancer risk.
| Study | Year | Geographic region | Study period | Design | Age, years | Case/ Control |
Range of Exposure (mg/d) | Adjustment for Covariates |
|---|---|---|---|---|---|---|---|---|
| Shibaba et al | 1992 | United states | 1981-1989 | Cohort | 68-82 | 208/3,789 | <145(T1); ≥210(T3) | Age, smoking, BMI, and physical activity |
| Daviglus et al | 1996 | United states | 1959-1989 | Cohort | 40-55 | 132/1,767 | ≤74(Q1); >121(Q4) | Age, number of cigarettes smoked per day, dietary cholesterol and saturated fat, ethanol intake, total energy intake, occupation, and education |
| Andersson et al | 1996 | Sweden | 1989-1994 | PCC | cases: 70.7(5.9); control: 70.6(6.2) | 526/536 | 35.7(T1); 86.1(T3) | Age, energy, BMI, physical activity, and nutrient residuals |
| Mayer et al | 1997 | United states | 1990-1993 | HCC | ≥ 45 | 215/593 | Q1-Q4, cut points were not mentioned | Age, education, family history of prostate cancer, BMI, physical activity, and dietary energy |
| Vlajinac et al | 1997 | Yugoslavia | 1990-1994 | HCC | cases: 70.5; control: 71.5 | 101/202 | <84.7(T1); ≥188.7(T3) | Energy, nutrients which were significant between cases and controls, physical activity, specific occupational exposure, nephrolithiasis, other diseases such as chronic bronchitis, chronic rheumatic diseases, hypertension, cardiomyopathia, diabetes mellitus, renal diseases, eye diseases and tuberculosis, greater number of brothers, greater number of sexual partners |
| Key et al | 1997 | UK | 1989-1992 | PCC | mean age of cases and controls were 68.1 | 328/328 | <66.1(T1); ≥104.3(T3) | Energy, social class, height, BMI, age, smoking, family history of prostate cancer, and nutrients intake |
| Demeo-Pellegrini et al | 1999 | Uruguay | 1994-1997 | HCC | 40-89 | 175/233 | ≤85.8(Q1); >161.9(Q4) | Age, residence, urban/rural status, education, family history of prostate cancer, BMI and total energy intake |
| Jain et al | 1999 | United states | 1989-1993 | PCC | cases: 69.8; controls: 69.9 | 617/636 | <121.08(Q1); >243.70(Q4) | Log total energy, vasectomy, age, smoked, marital status, study area, BMI, education, ever-used multivitamin supplements within 1 year, area of study, and log-converted amounts for grains, fruit, vegetables, total plants, total carotenoids, folic acid, dietary fiber, conjugated linoleic acid, vitamin E, retinol, total fat, and linoleic acid |
| Kristal et al | 1999 | United states | 1993-1996 | PCC | 40-64 | 697/666 | Q1-Q4, cut points were not mentioned | Fat, energy, race, age, family history of prostate cancer, BMI, PSA tests in previous 5 years, and education |
| Ramon et al | 2000 | Spain | 1994-1998 | HCC | matched by age (within 5 years) | 217/434 | 104.6(Q1); 165(Q4) | Age, smoking, marital status, number of children, residence, calories, family history, BMI, quartiles of animal fat and α-linolenic acid |
| Cohen et al | 2000 | United states | 1993-1996 | PCC | 40-64 | 628/602 | <70(Q1); ≥150(Q4) | Fat, energy, race, age, family history of prostate cancer, BMI, prostate-specific antigen tests in previous 5 years, education, and intake of fruits and vegetables per week and nutrients per day |
| McCann et al | 2005 | United states | 1986-1991 | PCC | controls were matched to cases on age | 433/538 | ≤139(Q1); >240(Q4) | Age, education, BMI, cigarette smoking status, total energy and vegetable intake |
| Kirsh et al | 2006 | United states | 1993-2001 | Cohort | 55-74 | 1,338/28,023 | 77(Q1); 268(Q5) | Age, total energy, race, study center, family history of prostate cancer, BMI, smoking status, physical activity, total fat intake, red meat intake, history of diabetes, aspirin use, and number of screening examinations during the follow-up period |
| Rohrmann et al | 2007 | United states | 1992-2000 | Cohort | 46-81 | 6,092/18,373 | 79(Q1); 265(Q5) | Age, race or ethnicity, cigarette smoking, BMI, leisure-time physical activity, alcohol consumption, energy intake, intake of protein, and intake of polyunsaturated fatty acids |
| Kristal et al | 2008 | United states | 1994-2003 | Cohort | 54-86 | 876/3,894 | <69.8(Q1); ≥194.0(Q5) | Age, race/ethnicity, waist/hip ratio, smoking, BMI, physical activity, and total energy |
| Bidoli et al | 2009 | Italy | 1991-2002 | HCC | 46-74 | 1,294/1,451 | <95.8(T1); ≥139.9(T3) | Age, study center, period of interview, education, physical activity, BMI, alcohol intake, smoking habits, family history of prostate cancer and total energy intake, according to the residual model |
| Lewis et al | 2009 | United states | 1998-2004 | PCC | cases: 63.3(8.2); controls:62.0(10.7) | 478/382 | ≤90.7(T1); ≥143.3(T3) | Age, education, BMI, smoking history, family history of prostate cancer in first-degree relatives, and total caloric intake |
| Roswall et al | 2013 | Denmark | 1993-2010 | Cohort | 50-64 | 1,571/25,285 | ≤70.6(Q1); >121.5(Q4) | Intake of folate, vitamin E, and beta-carotene for both dietary and supplemental exposure, height, weight, education, intake of red meat, alcohol consumption, selenium intake, smoking, and physical activity |
Abbreviations: HCC, hospital-based case-control study; PCC, population-based case-control study; BMI, body mass index; Q, quartile/quintile; T, tertile.
Range of exposure indicates the cutoff points for the highest and lowest categories of dietary vitamin C intake.