Reference
[1] Int J Vitam Nutr Res. 2004 Nov;74(6):403-19.
Enhancers of iron absorption: ascorbic acid and other organic acids.
Teucher B, Olivares M, Cori H.

[2] Structure and Function of Ferritin
Dr. Robert R. Crichton *
Max-Planck-Institut für Molekulare Genetik, Berlin-Dahlem, Ihnestrasse 63/73 (Germany)
*Correspondence to Robert R. Crichton, Max-Planck-Institut für Molekulare Genetik, Berlin-Dahlem, Ihnestrasse 63/73 (Germany)

[3] Screening for iron overload: Lessons from the Hemochromatosis and Iron Overload Screening (HEIRS) Study.
Adams P, Barton JC, McLaren GD, Acton RT, Speechley M, McLaren CE, Reboussin DM, Leiendecker-Foster C, Harris EL, Snively BM, Vogt T, Sholinsky P, Thomson E, Dawkins FW, Gordeuk VR, Eckfeldt JH.
Can J Gastroenterol. 2009 Nov;23(11):769-72.

[4] Genetic mechanisms and modifying factors in hereditary hemochromatosis.
Weiss G.

[5] Effect of tea and other dietary factors on iron absorption.
Crit Rev Food Sci Nutr. 2000 Sep;40(5):371-98.
Zijp IM, Korver O, Tijburg LB.
Unilever Research Vlaardingen, The Netherlands.
Iron deficiency is a major world health problem, that is, to a great extent, caused by poor iron absorption from the diet. Several dietary factors can influence this absorption. Absorption enhancing factors are ascorbic acid and meat, fish and poultry; inhibiting factors are plant components in vegetables, tea and coffee (e.g., polyphenols, phytates), and calcium. After identifying these factors their individual impact on iron absorption is described. Specific attention was paid to the effects of tea on iron absorption. We propose a calculation model that predicts iron absorption from a meal. Using this model we calculated the iron absorption from daily menus with varying amounts of enhancers and inhibitors. From these calculations we conclude that the presence of sufficient amounts of iron absorption enhancers (ascorbic acid, meat, fish, poultry, as present in most industrialized countries) overcomes inhibition of iron absorption from even large amounts of tea. In individuals with low intakes of heme iron, low intakes of enhancing factors and/or high intakes of inhibitors, iron absorption may be an issue. Depletion of iron stores enhances iron absorption, but this effect is not adequate to compensate for the inhibition of iron absorption in such an inadequate dietary situation. For subjects at risk of iron deficiency, the following recommendations are made. Increase heme-iron intake (this form of dietary iron present in meat fish and poultry is hardly influenced by other dietary factors with respect to its absorption); increase meal-time ascorbic acid intake; fortify foods with iron. Recommendations with respect to tea consumption (when in a critical group) include: consume tea between meals instead of during the meal; simultaneously consume ascorbic acid and/or meat, fish and poultry.

[6] Inal Research Communications
Inhibition of food iron absorption by coffee
TA Morck, SR Lynch and JD Cook
Dual isotope studies were performed in iron replete human subjects to evaluate the effect of coffee on nonheme iron absorption. A cup of coffee reduced iron absorption from a hamburger meal by 39% as compared to a 64% decrease with tea, which is known to be a potent inhibitor of iron absorption. When a cup of drip coffee or instant coffee was ingested with a meal composed of semipurified ingredients, absorption was reduced from 5.88% to 1.64 and 0.97%, respectively, and when the strength of the instant coffee was doubled, percentage iron absorption fell to 0.53%. No decrease in iron absorption occurred when coffee was consumed 1 h before a meal, but the same degree of inhibition as with simultaneous ingestion was seen when coffee was taken 1 h later. In tests containing no food items, iron absorption from NaFeEDTA was diminished to the same extent as that from ferric chloride when each was added to a cup of coffee. These studies demonstrate that coffee inhibits iron absorption in a concentration-dependent fashion.

[7] Adv Exp Med Biol. 1991;289:499-508.
The effect of food processing on phytate hydrolysis and availability of iron and zinc.
Sandberg AS.
Department of Food Science, Chalmers University of Technology, Gothenburg, Sweden.

[8][+] Effect of phytates on iron absorption.
Nutrition Research Newsletter, Feb, 1989
Although it is generally accepted that phytates inhibit iron absorption in humans, little is known about the relationship between the amount of phytate consumed and the extent of inhibition of iron absorption, or about effects of other food components on this interaction. In a study conducted at the University of Goteborg, Sweden, the effects of different phytate doses on iron absorption were measured with and without added meat or ascorbic acid. On successive days, healthy volunteers consumed wheat rolls with and without various doses of added sodium phytate. The phytate-free and phytate-supplemented rolls contained different radioisotopes of iron, enabling iron absorption from the two types of rolls to be measured separately. In some trials, 50 mg ascorbic acid or 50 g meat (as a hamburger patty) was given along with the rolls. There was a dose-response relationship between increasing amounts of phytate and increasing inhibition of iron absorption: 2 mg phytate inhibited absorption by 18%; 25 mg by 64%; and 250 mg by 82%. The addition of ascorbic acid significantly counteracted this inhibition at both 25 and 250 mg doses of phytate. The effect of meat was less well defined. It did not improve iron absorption at the 25 mg phytate dose level but did so at the 250 mg level. The authors observe that “the marked inhibitory effect of even small amounts of phytates” was unexpected, and that the ascorbic acid/phytate interaction has “wide nutritional implications.” Ideally, if the phytate content of a diet is high, ascorbic acid intake should also be high. “The most feasible way to improve iron nutrition in populations where the traditional diet has a high phytate content would probably be to increase the ascorbic acid content.”

[9] Article: Effect of Indonesian Fermented Soybean Tempeh on Iron Bioavailability and Lipid Peroxidation in Anemic Rats
Abstract
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Seiichi Kasaoka,† Mary Astuti,‡ Mariko Uehara,§ Kazuharu Suzuki,§ and Shiro Goto*§
Department of Nutrition, Faculty of Agriculture, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156, Japan, and Laboratory of Science of Food and Nutrition, Faculty of Agricultural Technology, Gadjah Mada University, Jalan Sosio Justitia Bulaksumur, Yogyakarta, Indonesia
J. AGRIC. FOOD CHEM., 1997, 45 (1), pp 195–198

[10] Oxalic acid does not influence nonheme iron absorption in humans: a comparison of kale and spinach meals.
Eur J Clin Nutr. 2008 Mar;62(3):336-41. Epub 2007 Apr 18.
Genannt Bonsmann SS, Walczyk T, Renggli S, Hurrell RF.
Institute of Food Science and Nutrition, ETH Zurich, Zurich, Switzerland. stefan.storcksdieck@ilw.agrl.ethz.ch
OBJECTIVE: To evaluate the influence of oxalic acid (OA) on nonhaem iron absorption in humans. DESIGN: Two randomized crossover stable iron isotope absorption studies. SETTING: Zurich, Switzerland. SUBJECTS: Sixteen apparently healthy women (18-45 years, 0.16). CONCLUSION: Potassium oxalate did not influence iron absorption in humans from a kale meal and our findings strongly suggest that OA in fruits and vegetables is of minor relevance in iron nutrition.