A Cochrane review included 67 studies with a total of 8506 menstruating, non-pregnant women. At the end of intervention, women receiving iron compared with no iron were significantly less likely to be anaemic, had a reduced risk of iron deficiency, and had a higher haemoglobin concentration (table ). Iron supplementation improved maximal and submaximal exercise performance, and appears to reduce symptomatic fatigue. Seven trials (n=901) reported on 'any side effect' and did not identify an overall increased prevalence of side effects from iron supplements (RR 2.14, 95% CI 0.94 to 4.86, low quality evidence) and 8 studies (n=1214) did not find any evidence of an increased prevalence of nausea. However, several studies identified an increased prevalence of gastrointestinal side effects, loose stools/diarrhoea, hard stools/constipation, or abdominal pain (table ).
| Outcomes (at end of therapy) | Relative effect (95% CI) | Number of participants (studies) |
|---|---|---|
| Anaemia | RR 0.39 (0.25 to 0.60) | 3273 (10) |
| Haemoglobin , g/L | Mean Difference 5.30 (4.14 to 6.45) | 6861 (51) |
| Iron deficiency | RR 0.62 (0.50 to 0.76) | 1088 (7) |
| Outcomes | Relative effect (95% CI) | Number of participants (studies) |
|---|---|---|
| GI side effects | RR 1.99 (1.26 to 3.12) | 521 (5) |
| Loose stools/diarrhoea | RR 2.13 (1.10 to 4.11) | 604 (6 ) |
| Hard stools/constipation | RR 2.07 (1.35 to 3.17) | 1036 (8) |
| Abdominal pain | RR 1.55 (0.99 to 2.41) | 1190 (7) |
Date of latest search: 12 November 2015