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. 2019 Mar 14;2019(3):CD007411. doi: 10.1002/14651858.CD007411.pub4

Comparison 2. Head‐to‐head antioxidant(s).

Outcome or subgroup title No. of studies No. of participants Statistical method Effect size
1 Live birth; type of antioxidant 1   Peto Odds Ratio (Peto, Fixed, 95% CI) Subtotals only
1.1 L‐carnitine vs L‐acetyl carnitine 1 30 Peto Odds Ratio (Peto, Fixed, 95% CI) 1.0 [0.13, 7.92]
1.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Peto Odds Ratio (Peto, Fixed, 95% CI) 0.34 [0.06, 1.79]
1.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Peto Odds Ratio (Peto, Fixed, 95% CI) 0.34 [0.06, 1.79]
2 Clinical pregnancy; type of antioxidant 2   Peto Odds Ratio (Peto, Fixed, 95% CI) Subtotals only
2.1 L‐carnitine vs L‐acetyl carnitine 1 30 Peto Odds Ratio (Peto, Fixed, 95% CI) 1.0 [0.13, 7.92]
2.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Peto Odds Ratio (Peto, Fixed, 95% CI) 0.34 [0.06, 1.79]
2.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Peto Odds Ratio (Peto, Fixed, 95% CI) 0.34 [0.06, 1.79]
2.4 Vitamin D + Calcium vs Vitamin E + Vitamin C 1 86 Peto Odds Ratio (Peto, Fixed, 95% CI) 5.13 [1.21, 21.79]
3 Total sperm motility at 3 months or less; type of antioxidant 8   Mean Difference (IV, Random, 95% CI) Subtotals only
3.1 Docosahexaenoic acid (DHA) 400 mg vs Docosahexaenoic acid 800 mg 1 19 Mean Difference (IV, Random, 95% CI) 7.40 [‐11.35, 26.15]
3.2 Ethylcysteine vs Vitamin E 1 10 Mean Difference (IV, Random, 95% CI) ‐1.90 [‐41.97, 38.17]
3.3 L‐acetyl carnitine + L‐carnitine vs Vitamin E + Vitamin C 1 138 Mean Difference (IV, Random, 95% CI) 23.10 [20.14, 26.06]
3.4 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 3.40 [‐3.73, 10.53]
3.5 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 4.80 [‐1.76, 11.36]
3.6 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 1.40 [‐6.42, 9.22]
3.7 Selenium vs combined antioxidants 1 46 Mean Difference (IV, Random, 95% CI) 3.20 [‐10.13, 16.53]
3.8 Vitamin C 200mg vs Vitamin C 1000mg 1 20 Mean Difference (IV, Random, 95% CI) ‐43.0 [‐67.10, ‐18.90]
3.9 Zinc vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐4.40 [‐14.21, 5.41]
3.10 Zinc vs Zinc + Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐2.80 [‐12.90, 7.30]
3.11 Zinc + Folic acid vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐0.60 [‐7.73, 6.53]
3.12 Zinc vs Zinc + Vitamin E 1 18 Mean Difference (IV, Random, 95% CI) ‐1.0 [‐13.00, 13.00]
3.13 Zinc vs Zinc + Vitamin E + Vitamin C 1 12 Mean Difference (IV, Random, 95% CI) ‐1.0 [‐19.66, 17.66]
3.14 Zinc + Vitamin E vs Zinc + Vitamin E + Vitamin C 1 18 Mean Difference (IV, Random, 95% CI) 0.0 [‐18.97, 18.97]
4 Total sperm motility at 6 months; type of antioxidant 3   Mean Difference (IV, Random, 95% CI) Subtotals only
4.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 4.10 [‐2.70, 10.90]
4.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 3.40 [‐2.87, 9.67]
4.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) ‐0.70 [‐7.73, 6.33]
4.4 N‐acetylcysteine (NAC) vs Selenium + N‐acetylcysteine (NAC) 1 234 Mean Difference (IV, Random, 95% CI) ‐4.40 [‐5.14, ‐3.66]
4.5 Selenium vs N‐acetylcysteine (NAC) 1 234 Mean Difference (IV, Random, 95% CI) 1.30 [0.56, 2.04]
4.6 Selenium vs Selenium + N‐acetylcysteine (NAC) 1 232 Mean Difference (IV, Random, 95% CI) ‐3.10 [‐3.85, ‐2.35]
4.7 Zinc vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐1.70 [‐6.42, 3.02]
4.8 Zinc + Folic acid vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) 0.90 [‐5.46, 7.26]
4.9 Zinc vs Zinc + Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐2.60 [‐9.13, 3.93]
5 Total sperm motility at 6 months (data not suitable for meta analysis)     Other data No numeric data
5.1 Folic acid vs Zinc + Folic acid     Other data No numeric data
5.2 Zinc vs Folic acid     Other data No numeric data
5.3 Zinc vs Zinc + Folic acid     Other data No numeric data
6 Total sperm motility at 9 months or more; type of antioxidant 1   Mean Difference (IV, Random, 95% CI) Subtotals only
6.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 3.70 [‐1.69, 9.09]
6.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 5.30 [‐0.73, 11.33]
6.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 1.60 [‐3.29, 6.49]
7 Progessive sperm motility at 3 months or less; type of antioxidant 5   Mean Difference (IV, Random, 95% CI) Subtotals only
7.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 4.0 [‐1.88, 9.88]
7.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 29 Mean Difference (IV, Random, 95% CI) 5.0 [‐0.68, 10.68]
7.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 29 Mean Difference (IV, Random, 95% CI) 1.0 [‐5.41, 7.41]
7.4 L‐acetyl carnitine + L‐carnitine vs Vitamin E + Vitamin C 1 138 Mean Difference (IV, Random, 95% CI) 13.30 [11.21, 15.39]
7.5 L‐carnitine vs Vitamin E + Vitamin C 1 63 Mean Difference (IV, Random, 95% CI) 30.50 [27.70, 33.30]
7.6 L‐carnitine + Vitamin E vs Vitamin E 1 113 Mean Difference (IV, Random, 95% CI) 14.10 [10.11, 18.09]
7.7 Vitamin D + Calcium vs Vitamin E + Vitamin C 1 86 Mean Difference (IV, Random, 95% CI) 6.90 [5.38, 8.42]
8 Progressive sperm motility at 6 months; type of antioxidant 1   Mean Difference (IV, Random, 95% CI) Subtotals only
8.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 6.30 [0.42, 12.18]
8.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 29 Mean Difference (IV, Random, 95% CI) 5.70 [0.10, 11.30]
8.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 29 Mean Difference (IV, Random, 95% CI) ‐0.60 [‐6.93, 5.73]
9 Progressive sperm motility at 9 months; type of antioxidant 1   Mean Difference (IV, Random, 95% CI) Subtotals only
9.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 3.80 [‐1.50, 9.10]
9.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 29 Mean Difference (IV, Random, 95% CI) 5.50 [‐0.11, 11.11]
9.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 29 Mean Difference (IV, Random, 95% CI) 1.70 [‐4.17, 7.57]
10 Sperm concentration at 3 months or less; type of antioxidant 7   Mean Difference (IV, Random, 95% CI) Subtotals only
10.1 Docosahexaenoic acid (DHA) 400 mg vs Docosahexaenoic acid (DHA) 800 mg 1 19 Mean Difference (IV, Random, 95% CI) ‐6.80 [‐41.87, 28.27]
10.2 Ethylcysteine vs Vitamin E 1 10 Mean Difference (IV, Random, 95% CI) 2.20 [‐16.65, 21.05]
10.3 L‐carnitine vs Vitamin E + Vitamin C 1 63 Mean Difference (IV, Random, 95% CI) 15.5 [12.49, 18.51]
10.4 L‐carnitine + Vitamin E vs Vitamin E 1 113 Mean Difference (IV, Random, 95% CI) 1.90 [‐10.52, 14.32]
10.5 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 1.70 [‐10.97, 14.37]
10.6 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 4.10 [‐9.17, 17.37]
10.7 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 2.40 [‐11.14, 15.94]
10.8 Selenium vs combined antioxidants 1 46 Mean Difference (IV, Random, 95% CI) 14.70 [‐6.51, 35.91]
10.9 Zinc vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐5.30 [‐23.38, 12.78]
10.10 Zinc + Folic acid vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐4.20 [‐22.22, 13.82]
10.11 Zinc vs Zinc + Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐1.10 [‐18.65, 16.45]
11 Sperm concentration at 6 months; type of antioxidant 3   Mean Difference (IV, Random, 95% CI) Subtotals only
11.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 5.90 [‐8.92, 20.72]
11.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 8.10 [‐5.54, 21.74]
11.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 2.20 [‐10.89, 15.29]
11.4 N‐acetylcysteine (NAC) vs Selenium + N‐acetylcysteine (NAC) 1 234 Mean Difference (IV, Random, 95% CI) ‐5.30 [‐6.86, ‐3.74]
11.5 Selenium vs N‐acetylcysteine (NAC) 1 234 Mean Difference (IV, Random, 95% CI) 0.80 [‐0.71, 2.31]
11.6 Selenium vs Selenium + N‐acetylcysteine (NAC) 1 232 Mean Difference (IV, Random, 95% CI) ‐4.5 [‐6.20, ‐2.80]
11.7 Zinc vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐9.5 [‐20.29, 1.29]
11.8 Zinc + Folic acid vs Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐1.5 [‐15.06, 12.06]
11.9 Zinc vs Zinc + Folic acid 1 80 Mean Difference (IV, Random, 95% CI) ‐8.0 [‐23.69, 7.69]
12 Sperm concentration at 6 months (data not suitable for meta analysis)     Other data No numeric data
12.1 Zinc vs Folic acid     Other data No numeric data
12.2 Zinc vs Zinc + Folic acid     Other data No numeric data
12.3 Folic acid vs Zinc + Folic acid     Other data No numeric data
13 Sperm concentration at 9 months or more; type of antioxidant 1   Mean Difference (IV, Random, 95% CI) Subtotals only
13.1 L‐carnitine vs L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 8.2 [‐0.07, 16.47]
13.2 L‐carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) 6.10 [‐3.74, 15.94]
13.3 L‐acetyl carnitine vs L‐carnitine + L‐acetyl carnitine 1 30 Mean Difference (IV, Random, 95% CI) ‐2.10 [‐10.24, 6.04]