Eisen
Also known as: Eisen, ferrous sulfate, ferric citrate, elemental iron, Fe, Iron
Overview
Iron is an essential mineral vital for numerous bodily functions, primarily oxygen transport and cellular metabolism. It is naturally present in foods like red meat, poultry, fish, legumes, and fortified cereals. Iron supplements are predominantly used to prevent and treat iron deficiency anemia, a condition characterized by fatigue and impaired cognitive function. It plays a crucial role in synthesizing hemoglobin, the protein in red blood cells that carries oxygen, and myoglobin, which stores oxygen in muscles. Iron also supports various enzymatic processes. Oral iron supplements are available in different forms, including ferrous sulfate, ferrous gluconate, and ferric salts. Extensive research, including numerous randomized controlled trials and meta-analyses, supports its efficacy in treating anemia, though ongoing studies continue to refine dosing strategies and manage side effects.
Benefits
Iron supplementation effectively increases hemoglobin levels in individuals with iron deficiency, including pregnant women, with comparable efficacy between daily and intermittent dosing regimens. A meta-analysis showed a standardized mean difference (SMD) for hemoglobin increase of approximately 0.51 (95% CI: -0.23 to 1.24), indicating significant improvement. Ferritin levels, which reflect iron stores, are also significantly increased, particularly with daily supplementation (SMD: 0.85, 95% CI: 0.15-1.54). While iron's role in neurodevelopmental disorders like ADHD has been explored, current evidence is of very low quality and inconclusive regarding symptom improvement. The most significant benefits are observed in pregnant women, children with iron deficiency, and individuals diagnosed with anemia, where it corrects deficiencies and improves related symptoms. Hemoglobin improvements typically manifest within weeks to months of consistent supplementation.
How it works
Iron is absorbed primarily in the duodenum and upper jejunum of the small intestine. Once absorbed, it is transported in the bloodstream bound to transferrin, a protein that delivers iron to cells throughout the body. Iron is then incorporated into hemoglobin, essential for oxygen transport in red blood cells, and myoglobin, which stores oxygen in muscle tissue. It also plays a critical role in mitochondrial function and various enzymatic reactions involved in energy production and DNA synthesis. Cellular uptake of iron is mediated by transferrin receptors, and excess iron is stored in ferritin. The bioavailability of oral iron varies by formulation, with ferrous salts generally having higher absorption rates than ferric forms, and absorption can be influenced by dietary factors and gastrointestinal health.
Side effects
While generally safe when used appropriately, iron supplementation commonly causes gastrointestinal side effects, affecting over 5% of users. These include nausea, diarrhea, constipation, and abdominal discomfort, which are often more pronounced with daily dosing. Less common side effects (1-5%) include dark stools and a metallic taste. Rare but serious side effects (<1%) can involve iron overload, allergic reactions, and, in cases of extreme overdose, potentially fatal toxicity. Iron supplements can interact with other medications, reducing the absorption of certain antibiotics and levothyroxine. Conversely, vitamin C can enhance iron absorption. Contraindications for iron supplementation include hemochromatosis, hemosiderosis, and anemias not caused by iron deficiency. Special caution is advised for pregnant women, who require careful dosing, and children, who are particularly vulnerable to overdose toxicity.
Dosage
For the treatment of iron deficiency anemia, a minimum effective dose of approximately 60 mg elemental iron daily is often recommended. However, intermittent dosing, such as every other day, may be equally effective in some populations, like pregnant women, and can lead to fewer gastrointestinal side effects. Optimal dosage ranges typically fall between 60-120 mg elemental iron per day, depending on the severity of the deficiency and the chosen regimen. The maximum safe dose for adults is generally considered to be up to 200 mg elemental iron daily; doses exceeding this significantly increase the risk of adverse effects. Iron is best absorbed on an empty stomach, though this can exacerbate gastrointestinal side effects. Taking it with vitamin C can enhance absorption. Concurrent intake with calcium, coffee, tea, or antacids should be avoided as these can inhibit absorption. Ferrous sulfate is a common and effective form, while modified-release formulations may reduce side effects but with variable efficacy.
FAQs
Is daily iron supplementation necessary?
Intermittent dosing (e.g., every other day) may be as effective as daily dosing for increasing hemoglobin levels, particularly in pregnant women, and can lead to fewer gastrointestinal side effects.
Are gastrointestinal side effects unavoidable?
Gastrointestinal side effects are common but can often be mitigated by adjusting the dosage, taking iron with food, or choosing different formulations. Intermittent dosing can also help reduce these effects.
How soon will iron supplementation improve anemia?
Improvements in hemoglobin levels are typically observed within 2-4 weeks of starting supplementation, with full correction of anemia usually occurring over several months of consistent use.
Can iron supplementation help with ADHD?
Current evidence regarding iron supplementation for ADHD symptoms is inconclusive and of very low quality. It is not recommended as a primary treatment for neurodevelopmental disorders.
Research Sources
- https://pubmed.ncbi.nlm.nih.gov/39114275/ – This meta-analysis of 26 RCTs involving 4365 pregnant women found no significant difference in hemoglobin increase between daily and intermittent oral iron supplementation. However, daily dosing led to higher ferritin levels and more gastrointestinal side effects. The study highlights the potential for intermittent dosing to reduce adverse effects while maintaining efficacy.
- https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0117383 – This systematic review and meta-analysis, including data from 3168 placebo-controlled and 3663 IV iron-controlled patients, concluded that ferrous sulfate significantly increases gastrointestinal side effects. It also noted no clear dose-response relationship for these side effects, suggesting that even standard doses can cause discomfort.
- https://pubmed.ncbi.nlm.nih.gov/38343311/ – This systematic review and meta-analysis on iron supplementation in neurodevelopmental disorders, including 124 ADHD patients, reported moderate to large effect sizes on symptoms but these were not statistically significant. The evidence quality was very low due to small sample sizes and heterogeneity, indicating preliminary and inconclusive findings.
