Post-prandial iron absorption in humans: comparison between HFE genotypes and iron deficiency anaemia.

BACKGROUND & AIMS: Measurement of serum iron increase after ingestion of a meal could be an efficient method of comparing post-prandial iron absorption between groups of individuals. We determined whether the rise in post-prandial serum iron is increased in fully treated patients with hereditary haemochromatosis (HFE C282Y+/+; HH) compared to iron deficiency anaemia (IDA), iron-replete heterozygous subjects (HFE C282Y+/-) and iron-replete controls (HFE C282Y-/-). METHODS: Serum iron increase was measured over 4h after a meal containing 13.1 mg non-haem iron. RESULTS: Post-prandial increase in serum iron was similar in treated HH versus IDA (P=0.54), but greater than control subjects (P<0.0001). In five HH patients, using (58)Fe as a tracer, the rate of iron absorption was increased (P<0.05) and serum non-transferrin bound iron showed a tendency to increase (P=0.06). Serum iron curves did not differ for heterozygous subjects and controls (P=0.65). CONCLUSIONS: Using the serum iron method we found a comparable increase in post-prandial iron absorption in treated HH and IDA compared with controls. While post-prandial iron absorption in the group heterozygous for the C282Y mutation was modestly increased relative to controls, this difference was not statistically significant.

A food-group based algorithm to predict non-heme iron absorption.

OBJECTIVE: To develop an algorithm to predict the percentage non-heme iron absorption based on the foods contained in a meal (wholemeal cereal, tea, cheese, etc.). Existing algorithms use food constituents (phytate, polyphenols, calcium, etc.), which can be difficult to obtain. DESIGN: A meta-analysis of published studies using erythrocyte incorporation of radio-isotopic iron to measure non-heme iron absorption. METHODS: A database was compiled and foods were categorized into food groups likely to modify non-heme iron absorption. Absorption data were then adjusted to a common iron status and a weighted multiple regression was performed. RESULTS: Data from 53 research papers (3,942 individual meals) were used to produce an algorithm to predict non-heme iron absorption (R(2) =0.22, P < 0.0001). CONCLUSIONS: The percentage non-heme iron absorption can be predicted from information on the types of foods contained in a meal with similar efficacy to that of food-constituent-based algorithms (R(2) = 0.16, P= 0.0001).

Proton pump inhibitors suppress absorption of dietary non-haem iron in hereditary haemochromatosis.

BACKGROUND AND AIMS: During the long-term treatment of patients with hereditary haemochromatosis (HH) the authors observed that proton pump inhibitors (PPI) reduced the requirement for maintenance phlebotomy. Gastric acid plays a crucial role in non-haem iron absorption and the authors performed a case review and intervention study to investigate if PPI-induced suppression of gastric acid would reduce dietary iron absorption in C282Y homozygous patients. METHODS: Phlebotomy requirements to keep serum ferritin approximately 50 microg/l before (mean 6.1 (SE 0.6) years) and during (3.8 (0.9) years) administration of a PPI were evaluated in seven patients and a post-prandial study was performed to determine whether PPIs reduce absorption of non-haem iron (14.5 mg) from a test meal in a further 14 phlebotomised patients with normal iron stores. RESULTS: There was a significant reduction (p<0.001) in the volume of blood removed annually before (2.5 (0.25) l) and while taking (0.5 (0.25) l) a PPI. Administration of a PPI for 7d suppressed absorption of non-haem iron from the meal as shown by a significant reduction (all p<0.01) in: area under the serum curve (2145 (374) versus 1059 (219)), % recovery of administered iron at peak serum iron (20.5 (3.2) versus 11.0 (2.0)%) and peak serum iron (13.6 (2.4) vs 6.1 (1.2) micromol/l) (all values are before vs during PPI). CONCLUSIONS: Administration of a PPI to patients with HH can inhibit the absorption of non-haem iron from a test meal and the habitual diet.

Serum iron curves can be used to estimate dietary iron bioavailability in humans.

Erythrocyte incorporation of isotopic iron (Fe) is the standard method for assessing iron bioavailability, but the process is expensive, technically difficult, and gives no information on the kinetics of absorption. The main objective of this study was to validate serum Fe curves as measures of dietary iron absorption because previous work demonstrated that serum iron curves can be generated with iron doses as low as 5-20 mg and that up to 20 mg iron can be added to meals without affecting relative absorption. In 3 studies, groups (n = 10, 10, 21) of Fe-deficient, mildly anemic women consumed meals of varying calculated Fe bioavailability, with and without added ferric chloride (10 mg Fe). Blood samples were collected at baseline and every 30 min for 4 h after the meal. Serum Fe concentrations were measured. Areas under the serum Fe curves and peak concentrations were used in different models to estimate Fe absorption and uptake. In 21 subjects, (58)Fe-enriched ferric chloride was added to the meals, and blood was taken 2 wk later to calculate red cell isotope incorporation. The addition of 10 mg Fe to test meals produced measurable serum iron curves even when the meal Fe bioavailability was low. Serum Fe curves were highly reproducible and were affected as expected by food composition. Even the single measurement at the estimated time of peak iron concentration was correlated significantly with erythrocyte incorporation of (58)Fe (r = 0.72, P < 0.0001). Hence the extent and rate of absorption of nonheme iron from meals, rather than in individuals, can be investigated with such subjects without the need for isotopes.