Iron deficiency is the most common nutritional deficiency in Europe. An estimated 30% of women of reproductive age and 8% of men have iron-deficiency anaemia. The prevalence is higher in certain populations: vegetarians and vegans (due to lower bioavailable plant-based iron), women with heavy menstrual bleeding, and people in low-income brackets where dietary diversity is limited.
Iron is essential for oxygen transport, energy production, and cognitive function. The body cannot synthesise iron — it must be obtained from food or supplementation. Once depleted, iron status must be restored through consistent dietary intake or supplemental replacement.
How iron deficiency develops
Iron loss exceeds iron intake. This can happen through multiple pathways:
In women: Menstrual bleeding is the primary cause of iron loss in reproductive-age women. A typical period results in 15–30 mg iron loss. Menorrhagia (heavy menstrual bleeding) can result in losses exceeding 100 mg per cycle — far beyond dietary replacement.
In men and postmenopausal women: The primary cause is gastrointestinal bleeding (occult or overt) or dietary insufficiency. Men have lower baseline iron stores than women because they lose no iron through menstruation.
In vegetarians and vegans: Plant-based iron (non-heme iron) is absorbed at 2–10% efficiency, compared to heme iron from meat (15–35% efficiency). A vegetarian consuming 18 mg dietary iron per day absorbs approximately 0.36–1.8 mg. A meat-eater consuming the same 18 mg absorbs 2.7–6.3 mg — 3–7 times higher bioavailability from the same total intake.
In older adults: Decreased gastric acid production (achlorhydria or hypochlorhydria) reduces iron absorption. Iron absorption requires an acidic environment to dissolve iron compounds and form absorbable complexes.
Once iron stores drop below a threshold (ferritin <12 ng/mL), iron-deficiency anaemia develops. At this point, haemoglobin synthesis cannot keep pace with red blood cell turnover.
Signs and symptoms of iron deficiency
Iron deficiency progresses through three stages: depleted stores (low ferritin, normal haemoglobin), iron-deficient erythropoiesis (low ferritin, low haemoglobin, but normal red blood cell count), and iron-deficiency anaemia (low ferritin, low haemoglobin, low red blood cell count).
Symptoms emerge slowly as iron stores drop. Early-stage deficiency may produce no noticeable symptoms. As deficiency progresses, symptoms include:
- Persistent fatigue and weakness, especially during physical exertion
- Shortness of breath at rest or with minimal activity
- Dizziness or lightheadedness, particularly when standing
- Pale skin, nail beds, and mucous membranes (pallor)
- Brittle nails (koilonychia — spoon-shaped nails — occurs in severe deficiency)
- Difficulty concentrating or “brain fog”
- Headaches
- Rapid or irregular heartbeat (tachycardia)
- Restless leg syndrome (urge to move legs, especially at night)
- Cravings for non-food items (pica) — ice, starch, dirt — unusual but reported in severe deficiency
Symptoms vary between individuals. Some people with borderline-low ferritin (12–20 ng/mL) experience significant fatigue, while others with lower levels may be asymptomatic. Genetics, overall fitness level, and comorbid conditions affect symptom presentation.
Testing: The science behind iron measurement
Iron status is assessed through multiple blood tests, not a single figure. Each test measures a different aspect of iron homeostasis:
Serum ferritin:The primary storage protein for iron. Ferritin levels reflect iron stores in the body. Normal range is typically 12–300 ng/mL, but optimal levels for symptom resolution are often higher (30–50 ng/mL). Low ferritin (<12 ng/mL) indicates depleted iron stores.
Serum iron: The amount of iron currently circulating in the blood bound to transferrin. Normal range is 60–170 µg/dL. However, serum iron fluctuates throughout the day and with food intake, making it a poor diagnostic marker on its own.
Total iron-binding capacity (TIBC):The total amount of transferrin (iron transport protein) available to carry iron. In iron deficiency, TIBC is elevated (>450 µg/dL) because the body is attempting to maximise iron transport despite low circulating iron. Elevated TIBC is a compensatory response.
Transferrin saturation: The percentage of transferrin actually carrying iron. Calculated as (serum iron ÷ TIBC) × 100. Normal is 20–50%. In iron deficiency, transferrin saturation drops below 16%.
Haemoglobin and haematocrit:Measure the oxygen-carrying capacity of blood. Haemoglobin <12 g/dL in women or <13.5 g/dL in men indicates anaemia. Haematocrit <36% in women or <41% in men also indicates anaemia.
Mean corpuscular volume (MCV):The average size of red blood cells. In iron deficiency, cells become smaller (microcytic); MCV <80 fL indicates microcytic anaemia.
| Test | Normal range | Iron deficiency |
|---|---|---|
| Serum ferritin | 12–300 ng/mL | Low (<12 ng/mL) |
| Serum iron | 60–170 µg/dL | Low |
| TIBC | <450 µg/dL | Elevated (>450 µg/dL) |
| Transferrin saturation | 20–50% | Low (<16%) |
| Haemoglobin (women) | ≥12 g/dL | Low (<12 g/dL) |
| Haemoglobin (men) | ≥13.5 g/dL | Low (<13.5 g/dL) |
| MCV | 80–100 fL | Low (<80 fL) |
The diagnostic pattern for iron deficiency is: low ferritin + low serum iron + elevated TIBC + low transferrin saturation + low haemoglobin + low MCV. A single low ferritin is suggestive but not definitive; the full panel confirms the diagnosis.
Why bioavailability matters in iron supplementation
Iron from supplements must be absorbed to replete stores. Absorption depends on several factors:
Chemical form: Iron exists as ferrous (Fe²⁺) or ferric (Fe³⁺). Ferrous iron is more readily absorbed than ferric. Ferrous sulfate is the most commonly used form in supplements, achieving 15–35% absorption under ideal conditions.
Delivery vehicle: Chelation (binding to amino acids or organic acids) can improve absorption. Iron chelated to amino acids may achieve higher bioavailability than unchelated iron salts.
Liposomal encapsulation: Liposomal iron bypasses some absorption barriers. Standard iron supplements rely on active absorption via iron transporters (DMT1, IREG1) which saturate at high doses. Liposomal iron can fuse directly with intestinal epithelial cells, delivering iron intracellularly without saturation. Moana Natura’s Liposomal Iron achieves 397.7 times higher bioavailability than standard iron powder at the same dose. When compared to iron tablet formulations combined with vitamin C (a known iron absorption enhancer), liposomal iron still achieves 44.4 times higher bioavailability.
This difference is clinically significant. A standard iron supplement at 15 mg requires saturation of finite iron transporters. A liposomal iron supplement at 15 mg bypasses transporter saturation entirely, allowing higher absorption per unit dose.
Iron supplementation: Dose, form, and duration
Typical supplemental iron doses range from 15–65 mg elemental iron per day. The lower end (15 mg) is used for mild deficiency or maintenance; the higher end (40–65 mg) is used for active deficiency correction.
Duration of supplementation depends on severity. Mild iron deficiency (ferritin 12–20 ng/mL) may resolve in 3–6 months with consistent supplementation. Moderate deficiency (ferritin <12 ng/mL with anaemia) typically requires 6–12 months. Severe deficiency may require longer.
Iron supplementation should be combined with dietary iron intake. A diet including heme iron sources (red meat, poultry, fish) or iron-rich plant sources (legumes, dark leafy greens, fortified grains) supports supplementation rather than replacing it.
Vitamin C significantly enhances iron absorption. A dose of 100–200 mg vitamin C taken with iron increases ferrous iron absorption by 3–4 fold. This is why some iron supplements are formulated with vitamin C, or why taking iron with orange juice (vitamin C-rich) is recommended.
Conversely, certain substances inhibit iron absorption: phytates (in grains and legumes), tannins (in tea and coffee), calcium (in dairy), and polyphenols (in chocolate and cocoa). Spacing iron supplementation 2–3 hours away from these foods improves absorption.
When to supplement: Indicators for iron replacement therapy
Iron supplementation is indicated when:
- Ferritin is low(<12 ng/mL) AND symptoms are present (fatigue, shortness of breath, cognitive difficulty)
- Haemoglobin is low(<12 g/dL in women, <13.5 g/dL in men) and iron studies confirm iron deficiency as the cause
- Ferritin is borderline-low (12–20 ng/mL) with significant symptoms affecting quality of life
Supplementation without testing is not recommended — iron overload (haemochromatosis) is also harmful, and supplementing when iron stores are adequate provides no benefit and poses risk of gastrointestinal irritation.
Testing should be repeated 6–8 weeks after starting supplementation to confirm response and adjust dose if needed.
EFSA-authorised claims for iron
The following claims are authorised under EU Regulation 432/2012 when a supplement provides at least 15% of the Nutrient Reference Value (14 mg) per daily serving:
- Iron contributes to the reduction of tiredness and fatigue.
- Iron contributes to normal energy-yielding metabolism.
- Iron contributes to normal oxygen transport in the body.
- Iron contributes to normal cognitive function.
Moana Natura’s Liposomal Iron provides 15 mg per 5 mL daily serving — 107% of the NRV — meeting the threshold for all four authorised iron claims.