Cochrane concludes daily iron supplements improves women’s overall activity
April 20 2016
A Cochrane review has concluded that daily iron supplementation effectively reduces the prevalence of anaemia and iron deficiency, raises haemoglobin and iron stores in menstruating women. As a result it improves exercise performance and reduces symptomatic fatigue.
However, there was not enough evidence to say whether iron supplementation improves cognitive performance in women, and the benefits came at the expense of increased gastrointestinal side effects. The study also found little difference between iron salts.
The study looked at research based on menstruating women taking daily oral iron for at least five weeks compared to no iron supplementation. Cochrane researchers identified 67 trials involving data from 8,506 women for the meta-analysis.
There was “high quality evidence that iron improves haemoglobin and produces changes in bowel function, but moderate quality evidence that iron reduces the prevalence of anaemia and iron deficiency. Evidence of the effects of iron on other outcomes, such as abdominal pain, is of low quality,” said the researchers. “There are no data on the effects of iron on mortality in this population group.”
Ferrous sulphate was the most commonly used source of iron , accounting for 33 studies, while ferrous fumarate was used in five studies. Carbonyl iron, ferrous carbonate, ferrous gluconate, ferric ammonium citrate, ferrous succinate and various other iron compounds were also noted, with doses ranging from 1mg to approximately 300mg of elemental iron a day. Study periods also ranged from one week to 24 weeks.
Among the findings drawn from the meta-analysis are that “there is no evidence of difference in efficacy between different iron salts.” The effects of iron supplementation on haemoglobin did not appear dose related, but increases in ferritin concentration were greater at higher doses. In addition, “providing iron for one to three months achieved greater increases in haemoglobin and ferritin than either shorter or more prolonged durations.”
While vitamin C appeared to possibly augment the beneficial effect of iron on anaemia prevalence the data was limited on this respect.
Discussing implications for practice, the researchers concluded that “daily iron supplementation appears to be an effective clinical and public health strategy for alleviating anaemia and iron deficiency, and for increasing haemoglobin and iron stores.”
In addition to daily iron supplementation improving maximal and sub-maximal exercise performance, “there is evidence, moreover, that iron supplementation improves fatigue scores, particularly among women with baseline fatigue.”
In order to reduce the risk of adverse effects, especially abdominal side effects, the researchers suggest that lower doses of iron, equivalent to no more than 30mg of elemental iron, for four to 12 weeks may provide the best balance between benefit and adverse effect profile.