Anaemia Flashcards
Iron Metabolism?
Iron Balance
• No mechanism to regulate iron excretion. Iron balance is maintained
via
– Regulation of Iron absorption
– Reutilisation of iron (eg iron from
erythrocytes)
– Storage of iron (ferritin)
Body Stores (4-5g) • Functional – Haemoglobin (60%) – Myoglobin (5%) – Enzymes (5%)
• Body Storage
– Ferritin (20%)
– Hemosiderin (10%)
– Transferrin (<0.1%)
Basal Iron Loss?
1 mg
Iron requirements: Factorial Method (menstruation)?
Menstrual Blood Loss:
• Median = 30ml/cycle
- Mean = 44ml/cycle
- 90th centile = 83.9ml/cycle
- EAR is based upon 75th centile = 52.4ml/cycle
Iron Requirements – Factorial Method (menstruation): 44ml/cycle
83.9ml/cycle
44ml/cycle: Total iron loss: 1.57mg/d LRNI:7.3mg/d EAR:10.5mg/d RNI:13.6mg/d
83.9ml/cycle:
LRNI:10.3mg/d
EAR:14.7mg/d
RNI:19.2mg/d
What are the biomarkers of Iron?
TIBC
Serum ferritin
Iron Absorption %
Serum Iron
Transferrin Saturation
Serum Transferrin Receptor
FEP
Erythrocytes
Anaemia and Health?
Method:
• 75 female (Hb 6.1 to 15.9g/dL)
• 18min treadmill test
Results:
• Performance
• Sig ↓in groups with [Hb] <12g/dL v >12g/dL
- Blood lactate
- Sig ↑in groups with [Hb] <10g/dL v >10g/dL
Conclusion:
• Physical work capacity was reduced in iron-deficiency anaemia.
Types of Dietary Iron?
- Heme Iron:
• Heme iron is bound to protein complexes (hemoglobin, myoglobin)
- Higher bioavailability (readily available)
- Heme iron provides 10-15% of dietary intake, but ~33% of the total iron absorbed
- Non-heme Iron:
• Is found as ferric iron (Fe3+)
- Lower bioavailability
- Absorption is greatly affected by enhancers and inhibitors
Dietary Sources:
• Animal sources (meat, seafood and poultry) contain both heme and non-heme
• Plant sources (cereals, legumes, vegetables, fruits, iron supplements) contain non-heme only.
Factors influencing iron absorption?
ENHANCERS: Meat, poultry, fish Vitamin C
INHIBITORS: Phytate & Inositol Soy protein Polyphenols & flavonoids Tea & Coffee Calcium & dairy Zinc
Inhibitor – Phytate?
Background/Context:
• Phytate is found in cereal grains, legumes, nuts, seeds, vegetables, fruit
Method:
• Iron absorption from wheat rolls (iron = 4.1mg) containing:
• No Phytate (0mg)
• Phytate (2-250mg).
Results: • Fe absorption decreased by: • 2mg phytate – 18% • 25mg phytate – 64% • 250mg phytate– 82%
Conclusion:
• Even small amounts of phytatecan inhibit iron absorption.
Inhibitor - Calcium?
Background/Context:
• Calcium is found in dairy food and green leafy vegetables
• Glass of milk (~300mg)
Method:
• Iron absorption from wheat rolls (3.8mg iron) containing
• Calcium (0,40,75,165,300, 600mg).
Results • Fe absorption: • ND between 40mg & 0mg • Sig ↓ (75 – 600mg) vs 0mg • ND between 300 & 600mg Hallberg et al (1991) AJCN 53: 112-119
Conclusion:
• Calcium may inhibit iron absorption via 1) DMT-1, 2) altered mucus layer
properties (mucin) or 3) prevent phytate degradation.
Enhancer – Vitamin C?
Method:
• Iron absorption from wheat rolls (iron =4.1mg) containing phytate (25 and 250mg) plus
• Vitamin C (50mg and 100mg)
Results:
• Fe absorption:
• Sig ↑on Vit C (50 & 100mg)
Conclusion:
• Vitamin C improves iron absorption and reverses the negative effects of phytate.
Dietary Iron Intake and Status?
Method
• Sedentary women completed a 12wk aerobic exercise program whilst ingesting a normal diet (PLA) or meat diet (DIET).
Results
• Total Iron Intake
- Sig ↑on DIET (11.8mg/d) v PLA (8.8mg/d)
- Heme Iron Intake
- Sig ↑on DIET (1.8mg/d) v PLA (1.0mg/d)
- Non-Heme Iron Intake
- Sig ↑on DIET (10mg/d) v PLA (7.8mg/d).
- Vitamin C Intake
- ND between groups
- Haematology
- Serum Ferritin – Sig ↑on DIET v PLA
- Hb – Sig ↑on DIET v PLA
Conclusion:
• Increasing iron intake (heme & non-heme) improves iron status (serum ferritin and Hb)
Dietary Iron Enhancers and Iron Status?
Method
• 75 females (non-anaemic) ingested PLA v DIET for 16wk
• Diet = Increased bioavailability
Results
• Total Iron Intake
- ND between trials (~12mg/d)
- Heme Iron Intake
- Sig ↑on DIET (1.9mg/d) v PLA (0.9)
- Non-heme Iron Intake
- ND between trials.
- Vitamin C Intake
- Sig ↑on DIET (235mg/d) v PLA (100mg/d)
- Phytate Intake
- Sig ↓on DIET
- Haematology
- Ferritin – Tended to ↑on DIET (P=0.068)
- Hb – ND between trials
Conclusion:
• An intensive diet program tended to improve iron status, despite no difference in total iron intake, highlighting potentialbenefit of enhancers.
Current Iron Intake and DRV in the UK?
Considerations for DRV
• Factorial Method (Iron Absorption = 15%)
• Anaemia (M: <130g/L or W: <120g/L)
• Note: Low iron stores = Serum Ferritin
(<15ug/L)
Current UK DRV
Male Female
• LRNI = 4.7mg/d LRNI = 8.0mg/d
- EAR = 6.7mg/d EAR = 11.4mg/d
- RNI = 8.7mg/d RNI = 14.8mg/d
Current UK Intake
• Men = 12.4 ± 5.3mg/d
- Women = 11.2 ± 9.5mg/d
- Only 1% of men, but 23% of women consume
Folate DRV and Current Intake?
Considerations for DRV
• Megaloblastic anaemia
• (Neural tube defects)
Current UK DRV
• LRNI =100μg/d
- EAR = 150μg/d
- RNI = 200μg/d
Current UK Intake
• Men = 303 ± 138μg/d
• Women = 272 ± 292μg/d
• Only 4% of women and 2%
of males consume less than
LRNI.
Dietary Sources
• Rich folate sources include liver, pulse, green leafy vegetables and oranges
Safe Upper Limit
- Guidance level =1mg/d (supplemental) or 1.5mg/d (combined)
- Driver - Masking vitamin B12 deficiency
