Chili, but not turmeric, inhibits iron absorption in women from an iron-fortified composite meal

The Journal of NutritionNutrient Physiology,Metabolism,and Nutrient-Nutrient InteractionsChili,but Not Turmeric,Inhibits Iron Absorptionin Young Women from an Iron-FortifiedComposite Meal1Siriporn Tuntipopipat,2Kunchit Judprasong,2Christophe Zeder,3Emorn Wasantwisut,2Pattanee Winichagoon,2Somsri Charoenkiatkul,2Richard Hurrell,3and Thomas Walczyk3*2Institute of Nutrition,Mahidol University,Nakhon Pathom,Thailand and3Laboratory of Human Nutrition,Institute of Food Scienceand Nutrition,CH-8092Zurich,SwitzerlandAbstractChili and turmeric are common spices in indigenous diets in tropical regions.Being rich in phenolic compounds,they wouldbe expected to bind iron(Fe)3in the intestine and inhibit Fe absorption in humans.Three experiments were conducted inhealthy young women(n¼10/study)to assess the effect of chili and turmeric on Fe absorption from a rice-based mealcontaining vegetables and iron fortifiedfish sauce in vivo.Iron absorption was determined by erythrocyte incorporation ofstable isotope labels(57Fe/58Fe)using a randomized crossover design.Addition of freeze-dried chili(4.2g dry powder,25mg polyphenols as gallic acid equivalents)reduced Fe absorption from the meal by38%(6.0%with chili vs.9.7%withoutchili,P¼0.0017).Turmeric(0.5g dry powder,50mg polyphenols as gallic acid equivalents)did not inhibit iron absorption(P¼0.91).A possible effect of chili on gastric acid secretion was indirectly assessed by comparing Fe absorption from acidsoluble[57Fe]-ferric pyrophosphate relative to water soluble[58Fe]-ferrous sulfate from the same meal in the presence andabsence of chili.Chili did not enhance gastric acid secretion.Relative Fe bioavailability of ferric pyrophosphate was5.4%inpresence of chili and6.4%in absence of chili(P¼0.47).Despite the much higher amount of phenolics in the turmericmeal,it did not affect iron absorption.We conclude that both phenol quality and quantity determine the inhibitory effect ofphenolic compounds on iron absorption.J.Nutr.136:2970–2974,2006.IntroductionIron deficiency is the most common micronutrient deficiency inthe world(1).Iron deficiency,and consequently iron deficiencyanemia(IDA),4develops when iron intake does not meet ironrequirements over the long term.Children and women ofchildbearing age,with higher demands for iron due to growthand menstrual blood loss,are most vulnerable.Low iron status ismore frequently observed in populations living on plant-baseddiets that are low in muscle tissue(2).Although meat can providehighly bioavailable heme iron(3)and is known to enhance dietarynonheme iron absorption(4–7),plant-based diets are commonlyhigh in phytic acid and polyphenolic compounds as potentinhibitors of iron absorption.Primary sources of polyphenols inthe diet are vegetables and beverages,including wine.Herb tea,black tea,or coffee strongly inhibit iron absorption in a dose-dependent manner from a simple meal of bread(8).Similar obser-vations have been made in humans for phenolic-rich extractsfrom rosemary(9).In Thailand,the local vegetable Yod kratin(lead tree leaves,Leucaena glauca),reduced iron absorption by90%in a composite meal of rice,fish,and vegetables(10).Herbs and spices are used extensively as condiments incountries across the tropical belt,including Thailand(11–13),and may affect iron absorption due to high phenolic content(14).In the present study,we evaluated the effect of chili and turmeric,two of the most common spices in Asia,on iron absorption.Chiliin its various forms(genus Capsicum)contains high amounts ofphenolic compounds,including capsaicin(15,16).On the otherhand,peppers(including chili)and capsaicin were found toincrease gastric acid secretion in the rat model(17–19).Gastricacid is essential for releasing iron from the food matrix and forsolubilization in the stomach(20).This refers in particular to ironcompounds that are poorly soluble in water and need to be dis-solved in the gut to make the iron accessible.Turmeric(Curcumalonga),the other spice under investigation,is used extensivelyin the Indian subcontinent and parts of South East Asia(11–13).Turmeric is well known for its antioxidative and anti-inflammatoryproperties(21,22).Curcumin,alowmolecularweightpolyphenolic diketone,is the most active constituent of turmericand forms complex solubilized iron in aqueous solution(23–25).The aim of the present study was to1)evaluate the effect ofchili pepper and turmeric on human iron absorption and2)1Supported by the International Atomic Energy Agency(IAEA)Vienna underthe Doctoral Coordinated Research Project on isotopic and complementary toolsfor the study of micronutrient status and interactions in developing countrypopulations.4Abbreviations used:CRP,C-reactive protein;P:reference meal with iron addedas[57Fe]-ferric pyrophosphate;P1C,reference meal with added chili and ironadded as[57Fe]-ferric pyrophosphate;RBV,relative bioavailability;R,referencemeal with iron added as[57Fe/58Fe]-FeSO4;R1C,reference meal with added chiliand iron added as[57Fe/58Fe]-FeSO4;R1T,reference meal with added turmericand iron added as[57Fe/58Fe]-FeSO4.*To whom correspondence should be addressed.E-mail:thomas.walczyk@ilw.agrl.ethz.ch.29700022-3166/06$8.00ª2006American Society for Nutrition.Manuscript received31May2006.Initial review completed7July2006.Revision accepted14September2006.by guest on August 9, 2013Downloaded fromidentify in vivo a possible effect of chili on gastric function by comparing iron absorption from ferric pyrophosphate as an acid-soluble iron compound to ferrous sulfate as a water-soluble iron compound in the presence and absence of chili.Absorption studies were conducted in Thailand by stable isotope techniques and based on erythrocyte incorporation of iron stable isotopic labels from an iron-fortified,rice-based meal.Material and MethodsSubjects.Thirty apparently healthy,adult women(;18–35y of age with a maximum body wt of60kg)were recruited at Mahidol University,Thailand.Exclusion criteria included pregnancy,lactation, gastrointestinal disorders,or metabolic diseases.The absence of thalas-semia was verified by hemoglobin typing using a commercial HPLC-based auto-analyzer(Variant,Bio-Rad).The volunteers were asked to refrain from vitamin or mineral supplements and medication,except oral contraceptives,starting2wk before the study until the last blood sample was drawn.The study protocol was approved by the Ethical Committees of Mahidol University,Thailand,and ETH Zurich,Switzerland.Written informed consent was obtained from all volunteers.Study design.Thirty women were randomly allocated to the3separate studies.All volunteers consumed2test meals on consecutive days: reference meal(R)and reference meal1chili(R1C)in study1;and R and reference meal1tumeric(R1T)in study2.Meal R consisted of rice and a vegetable soup that was seasoned with iron-fortifiedfish sauce.Isotopi-cally labeled iron was added as ferrous sulfate to thefish sauce in the meals and administered in a randomized crossover design(R/R1C or R1C/R).Iron absorption from isotopically labeled[57Fe]-pyrophosphate was measured from meal R in absence(meal P)or presence of chili(meal P1C).Iron absorption from meals P and P1C was compared directly in each subject to iron absorption from water-soluble[58Fe]-FeSO4(meal R).Test meals were administered pair wise(R/P and R/P1C)on2con-secutive days using a randomized crossover design with a2wk interval between the2feeding regimens.All test meals were consumed in the morning between0700and0900 after an overnight fast under standardized conditions and under close supervision of the investigators.Before serving thefirst meal,a venous blood sample was drawn to determine iron status parameters(hemo-globin and plasma ferritin concentration)and body weight and height were measured.In addition,C-reactive protein(CRP)concentration was measured to determine the presence of infection.No intake of food or fluids was allowed for3h after test meal intake.A second venous blood sample was drawn14d after intake of the second test meal(d16).In study3,a third blood sample was taken14d after administration of the last test meal(d31).Recovery of isotopic labels in the drawn blood samples were used to calculate fractional iron absorption.Test meals.All test meals were based on a basic Thai-style dish used in an earlier study(26).The basic meal consisted of steamed white rice (50g dry weight)served with a soup prepared from local vegetables(50g white cabbage,50g Chinese cabbage,30g Thai mushrooms and20g steamed carrots).Vegetables and rice were purchased in bulk and individual portions were prepared using standardized procedures(26). For consumption,120mL of water and12mL commercialfish sauce were added to the defrosted vegetables and the soup was warmed in a microwave oven using a standardized heating program.Each meal contained;4mg of isotopically labeled fortification iron, either as[57Fe/58Fe]-ferrous sulfate or[57Fe]-ferric pyrophosphate(see Table1).In studies1and2,isotopically labeled ferrous sulfate was added to thefish sauce before adding to the soup.This corresponds to the use of ferrous sulfate fortifiedfish sauce at a fortification level of;350 mg Fe/L(26).In study3,[58Fe]-ferrous sulfate was added likewise to the fish sauce(meal R),whereas meals P and P1C were prepared by adding [57Fe]-ferric pyrophosphate to the steamed rice and by seasoning the vegetable soup with unfortifiedfish sauce.For preparation of test meals R1C and P1C,4.2g of ground lyophilized Thai chili(Capsicum annuum)was added to the soup shortly before consumption(14.2g fresh wt,25.260.2mg polyphenols as gallic acid equivalents).Test meal R1Twas prepared by steaming0.50g ground lyophilized turmeric per serving(2.8g fresh wt containing50.1360.06 mg total polyphenols as gallic acid equivalents)with the rice.Ferric pyrophosphate was weighed in individual portions in plastic containers and added to the meal.The exact amount added to the meal was determined by reweighing the plastic containers.High purity water (18mol/L V,250g)was served as a drink with all test meals.Quantitative intake of isotopic labels was ensured by rinsing the bowls3times with 10mL deionized water and by letting the subject consume the washings. Preparation of isotopically labeled iron.Isotopically labeled[57Fe]-ferrous sulfate and[58Fe]-ferrous sulfate were prepared at ETH Zurich by dissolution of isotopically enriched elemental iron([57Fe]-metal:95.9% enriched;[58Fe]-metal:93.2%enriched;both Chemgas)in diluted sulphuric acid.[57Fe]-Ferric pyrophosphate was prepared in food grade quality from57Fe enriched elemental iron([57Fe]-metal:95.9%enriched, Chemgas)by Lohmann Chemicals(Emmerthal).The compound was prepared using a scaled-down procedure used for the production of the commercial product.Eighteen hours before the test meal was adminis-tered,labeled iron solutions([57Fe]-ferrous sulfate and[58Fe]-ferrous sulfate)were added gravimetrically to thefish sauce in bulk along with citric acid(3g/L)and potassium iodide(4.2mg/L)to comply with the formulation of the fortified product previously described(26).Iron absorption measurements.Isotopically labeled compounds and collected blood samples were analyzed for isotopic composition at ETH Zurich by multicollector negative thermal ionization mass spectrometry as described earlier(27,28).Based on the shift of the Fe isotope ratios in the blood samples and the amount of Fe circulating in the body,amounts of57Fe and58Fe isotopic labels presented in the blood14d after test meal administration were calculated based on the principles of isotope dilution and considering that the used Fe isotopic labels were not mono-isotopic(28).Circulating Fe was calculated based on blood volume and hemoglobin concentration(29).Blood volume calculations were basedTABLE1Administered test meals and added amounts of isotopically labeled iron and spices1Study Test meal Composition21R Basic meal157FeSO4(3.9260.01mg57Fe)or58FeSO4(4.0960.05mg58Fe)R1C Basic meal157FeSO4(3.9260.01mg57Fe)or58FeSO4(4.0860.05mg58Fe)1chili(4.2360.05g)2R Basic meal157FeSO4(3.9260.02mg57Fe)or58FeSO4(4.1060.01mg58Fe)R1T Basic meal157FeSO4(3.9260.02mg57Fe)or58FeSO4(4.1060.01mg58Fe)1turmeric(0.50160.001g)3.1R Basic meal158FeSO4(4.1160.01mg58Fe)P Basic meal157Ferric pyrophosphate(4.2060.21mg57Fe)3.2R Basic meal158FeSO4(4.0960.04mg58Fe)P1C Basic meal157Ferric pyrophosphate(4.0560.09mg57Fe)1chili(4.2560.03g)1Values are means6SD,n¼10/study.2The basic meal consisted of rice,vegetable soup,and distilled water.Spices and iron absorption2971 by guest on August 9, 2013 Downloaded fromon height and weight according to Brown et al.(30).For calculations of fractional iron absorption,80%incorporation of the absorbed Fe into red blood cells was assumed(31).Blood analysis.Venous blood samples(5mL)were collected in EDTA-treated tubes and analyzed for complete blood counts(CBC)using an ADVIA120Hematology System(Bayer).Plasma ferritin(normal range: 15–300m g/L)and CRP(,5g/L in absence of infection)were analyzed by chemiluminescent immunometric assay(IMMULITE/Ferritin and IMMULITE/High Sensitive CRP,DPC,CA)using low-and high-level quality control materials supplied by the company.Food analysis.Food samples were analyzed for iron and calcium by flame atomic absorption(SpectrAA400,Varian)after mineralization by wet digestion using a HNO3/perchloric acid mixture.The phytic acid content was determined by anion-exchange chromatography(32). Ascorbic acid was analyzed by HPLC according to the methods described by Sapers(33)and Parviainen and Nyssonen(34)using a reversed phase column and photometric detection.Dehydroascorbic acid was reduced to ascorbic acid prior to analysis by addition of dithiothritol (Fluka).Total polyphenol content as gallic acid equivalents was determined by the Folin-Ciocalteu method(35).Statistics.All calculations and statistical analyses were performed using commercially available spreadsheet programs and in-house calculation programs developed by ETH Zurich.Iron absorption was logarithmi-cally transformed before statistical analysis.Student paired t test was used to evaluate data within each study.Student unpaired t test was used to compare relative bioavailability(RBV)of ferric pyrophosphate to ferrous sulfate between studies3.1and3.2.Results are presented as means(61SD)unless otherwise noted.Differences in iron absorption between test meals were considered significant at P,0.05.Studies were powered to resolve a30%difference in iron absorption between test meals using each volunteer as her own control(studies1–3)and to resolve a50%difference in RBV in study3(95%CI).ResultsSubjects.None of the volunteers were anemic.Their hemoglobin concentration was134g/L(range:124–148g/L).Plasma ferritin concentrations were in the normal range for most subjects(geomet-ric mean:53m g/L,range:13–262).Two subjects in study2and 1subject in study3were marginally iron deficient(plasma ferritin concentration,15.0m g/L).One subject showed a marginally elevated CRP concentration of5.6g/L,indicative of a mild infection (mean concentration:0.9g/L,range:0.1–5.6for all subjects). Test meals.Total iron content of the meal was4.70–4.84mg (4.00mg from fortified compound,0.56mg from vegetables, 0.14mg from rice,and0.14mg from chili)(Table2).Calcium contents were low(29.4–32.7mg/meal).Phytic acid was higher in test meals with added chili(76.2mg,meals R1C and P1C)than meals R and R1T(58.9mg).Vitamin C was found to be neg-ligible in all meals,which can be attributed to the warming of meals before serving and the use of lyophilized chili and turmeric. Iron absorption.Results are presented as geometric means(21 SD,11SD)for iron absorption(studies1–3)and as RBV relative to ferrous sulfate for ferric pyrophosphate(study3)(see Table 3).In study1,iron absorption from ferrous sulfate fortifiedfish sauce with and without addition of chili was6.0(2.2,16.5)% and9.7(3.9,24.6)%,respectively.This translates into an inhibition of iron absorption by38%from the added chili(P¼0.0017).In study2,turmeric had no influence on iron absorp-tion.Mean iron absorption was8.9(3.2,24.4)%in the presence of tumeric and8.7(3.8,19.8)%in the absence of turmeric(P¼0.91).In study3.1,iron absorption from ferric pyrophosphate was much lower than that from ferrous sulfate(geometric mean 0.7vs.10.4%,P,0.0001).In study3.2,the addition of chili pepper did not improve iron absorption from ferric pyrophos-phate.Thus,chili did not significantly effect iron absorption from ferric pyrophosphate relative to ferrous sulfate(RBV with chili was5.4%vs.without chili6.4%,P¼0.47).Based on the observed intra-and inter-individual differences in iron absorption,the power of the study(95%CI)would have allowed detection of a minimal relative difference in iron absorp-tion between test meals of32%in study1,49%in study2,26% in study3.1,and49%in study3.2,respectively.The detection limit for a relative difference in RBV in study3was50%. DiscussionIn this study we have demonstrated that freeze-dried,ground chili pepper(14.2g fresh wt;25mg polyphenols as gallic acid equivalents)reduced iron absorption from a basic rice and vegetable meal by38%(P¼0.0017).A cross-sectional pilot dietary survey in Northeast Thailand(36)showed that chili intake varies considerably in adult Thais depending on their preference for spicy foods.The intake of chili per dish at each meal was assessed by weighing individual ingredients of popular northeast dishes and ranged from1.0to17.2g chili(fresh wt), TABLE3Effect of chili(studies1and3)and turmeric(study2) ingestion on iron absorption in women after a basictest meal1StudyPlasmaferritin Test mealFeabsorption RBV m g/L%167R basic meal1FeSO49.7a(3.9,24.4)–(28,119)R1C basic meal1FeSO41chili 6.0b(2.2,16.5)–249R basic meal1FeSO48.7a(3.8,19.9)–(13,262)R1T basic meal1FeSO41turmeric8.9a(3.3,24.1)–3.149R basic meal1FeSO410.4a(3.8,28.7) 6.4(14,125)P basic meal1ferricpyrophosphate0.7c(0.3,1.5)(4.5,13.3)3.2R basic meal1FeSO49.9a(3.9,24.6)5.4P1C basic meal1ferricpyrophosphate1chili0.5c(0.3,1.0)(1.9,16.5)1Values are geometric means(range),n¼10.Means in a column with superscripts without a common letter differ,P,0.05.2In study3,chili did not affect RBV(range in parentheses)of iron from ferric pyro-phosphate relative to FeSO4(P¼0.47).TABLE2Content of iron,calcium,phytic acid and ascorbic acid of test meal ingredientsFood Native iron Calcium Phytic acid Ascorbic acidmgRice0.14 2.827.0ND1 Vegetables20.5627.030.021.0 Turmeric0.010.48 1.9NDChili(lyophilized)0.14 3.319.2 1.71Not determined,assumed to be negligible.2After defrosting.2972Tuntipopipat et al. by guest on August 9, 2013 Downloaded fromwhich corresponds to0.25–4.0g dry wt.Thus,the amount of chili in our test meals was on the high end but still within the range of habitual chili intake.The polyphenol content of the fresh chili,however,was at620mg/100g,which was rela-tively low compared with the range of750–1300mg/100g that we found in8samples obtained from different local markets in Bangkok and Northeast Thailand during the dry and wet season.By adding a relatively large amount of chili to the meal, phytic acid content was increased from57to76mg in the meal. However,at a molar ratio of1.3:1of phytic acid to iron in the chili meal,it appeared unlikely that phytic acid had a significant effect on iron absorption(37).This allowed us to conclude that iron binding to phenolic compounds is the primary mechanism by which chili pepper inhibits nonheme iron absorption in humans.The known enhancing effects of chili and capsaicin on gastric acid secretion are apparently not of relevance to iron nutrition.Chili had no significant effect on iron absorption from acid-soluble ferric pyrophosphate relative to ferrous sulfate (RBV with chili5.4%vs.without chili6.4%,P¼0.47)in our study.Higher output of gastric juice and a lowering of gastric pH from chili would have resulted in an increased dissolution of ferric pyrophosphate and,therefore,an increase in RBV.Although chili inhibited iron absorption,turmeric did not, despite the greater content of total phenols in the meal con-taining added turmeric.Total phenols amounted to25mg and50mg for added chili and turmeric,respectively.In an earlier study,intake of20–50mg total polyphenols from black tea or herb tea containing polymers offlavonoid-gallic acid esters and monomericflavonoids reduced iron absorption from an iron-fortified bread roll by50–70%(8).This compares well with our findings for chili,but not for turmeric,in our more complex meal.These apparently inconsistent observations reflect the prin-cipal difficulties in assessing the effect of plant polyphenols on iron absorption.Phenolic metabolism in plants is complex and yields a wide array of compounds ranging from monomeric tan-nins andflavonoids and their condensation and glycosylation products to the complex lignans of the plant cell wall(38). Accordingly,polyphenol composition and structures vary sub-stantially between plant species and even within the plant.In turmeric,curcumin is the major bioactive compound and con-tains2phenolic groups and1diketone group whereas capsaicin is the most prominent phenolic compound in chili but contains only1phenolic hydroxyl group(39)(see Fig.1).At the same time,both spices contain theflavonoid quercetin(Fig.1)but at much different concentrations,i.e.,92.5mg/kg dry wt for tur-meric compared with829mg/kg dry wt for chili(15,16).The difficulty in making comparisons across studies or between different plant foods or polyphenol-containing drinks lies in the structural diversity of the phenolic compounds. Although phenolic compounds can bind iron,in principle,they may differ considerably in the mechanisms of iron binding as well as in their potency to make iron unavailable for absorption at intestinal pH.As an example,capsaicin can bind iron only through its single phenolic hydroxyl group whereas curcumin can bind iron both through interaction with its2aromatic hydroxyl groups as well as by chelation through its diketone functionality(23,24,40).The stability of the formed complexes depend not only on pH and redox potential of the digested food but also on interaction with other iron-binding compounds such as phytic acid and ascorbic acid in the gut,which are difficult to predict for a complex meal such as the one used in our study. These differences are not reflected in the total phenol contents as determined by the Folin-Ciocalteau method.The Folin-Ciocalteau reagent oxidizes phenolates and reduces the hetero-poly acids to a blue molybdenum-tungsten complex(35).The method delivers,therefore,only an estimate for the total numberof aromatic hydroxyl groups and no information about the stability of the iron complex at gastric pH.Other available methods for polyphenol analysis are only sensitive to certain phe-nolic structural units,such as condensed polyphenols(proan-thocyanidins)for the vanillin assay(41).HPLC analysis allows quantification of individual phenolic compounds in a sample (42)but,likewise,delivers no information about their potency to inhibit iron uptake in the gut.In conclusion,dietary contentsof phenolic compounds per se,despite the applied analytical method,are of limited value in predicting their inhibitory effecton iron absorption in vivo.Although phenolic content may serveas a qualitative predictor of iron bioavailability,it is difficult or even impossible to predict its quantitative effect on iron absorp-tion by the human body,which became apparent in our study.Thefindings from our study are important insofar as chili is a common spice across the tropical belts.However,ourfindings donot necessarily indicate that chili intake is a potential risk factor foriron nutrition.The basic test meal in our study was fairly neutral regarding enhancers and inhibitors of iron absorption.In a mealthat is already high in phytic acid and polyphenols,the additional polyphenol intake from chili may have a much less pronounced effect on iron absorption.The effect of polyphenols on iron absorption was found to reach a plateau at;100–200mg polyphenols per serving(8,42).In addition,the inhibitory effectof chili would be expected to be lower with the use of fresh chili instead of dried chili powder as used in our study.Lyophilization ofchili would be expected to decrease its content in ascorbic acid as a known enhancer of iron absorption.For both chili and turmeric,the presence of a dose-response effect must also be considered when settingfindings into a dietary context.Although amounts ofchili were relatively high in our meals,as typically found in South-east Asia,the Thai meal under investigation contained relativelylow amounts of turmeric.At higher amounts,such as those used inthe Indian subcontinent,turmeric may have an inhibitory effect oniron absorption,but this remains to beinvestigated.Figure1Chemical structures of curcumin,capsaicin,and quercetin as major phenolic compounds in turmeric and chili pepper.Spices and iron absorption2973by guest on August 9, 2013Downloaded fromAcknowledgmentsWe thank Dr.Ratchanee Kongkachuichai and Dr.Visith Chavasith from the Institute of Nutrition at Mahidol University for technical assistance;Ms.Pudsadee Siriprapa,Ms.Atitada Boonpraderm,Ms.Napaporn Riabroy,Mr.Somjai Klinkuan, Mr.Sueppong Gowachirapant,and ksana Chaimongkol for test meal preparation.Literature Cited1.World Health Organization,United Nations Children’s Fund,andUnited Nations University.Iron deficiency anemia assessment,preven-tion,and control.Geneva:WHO;2001.2.Bhargava A,Bouis HE,Scrimshaw NS.Dietary intakes and socioeco-nomic factors are associated with the hemoglobin concentration of Bangladeshi women.J Nutr.2001;131:758–64.3.Lopez MAA,Martos FC.Iron availability:An updated review.Int JFood Sci Nutr.2004;55:597–606.4.Martinez-Torres C,Layrisse M.Iron absorption from veal muscle.Am JClin Nutr.1971;24:531–40.5.Cook JD,Monsen ER.Food iron absorption in human subjects.parison of the effect of animal proteins on nonheme iron absorption.Am J Clin Nutr.1976;29:859–67.6.Engelmann MD,Davidsson L,Sandstrom B,Walczyk T,Hurrell RF,Michaelsen KF.The influence of meat on nonheme iron absorption in infants.Pediatr Res.1998;43:768–73.7.Baech SB,Hansen M,Bukhave K,Jensen M,Sorensen SS,Kristensen L,Purslow PP,Skibsted LH,Sandstrom B.Nonheme-iron absorption froma phytate-rich meal is increased by the addition of small amounts ofpork meat.Am J Clin Nutr.2003;77:173–9.8.Hurrell RF,Reddy M,Cook JD.Inhibition of non-haem iron absorption inman by polyphenolic-containing beverages.Br J Nutr.1999;81:289–95.9.Samman S,Sandstrom B,Toft MB,Bukhave K,Jensen M,Sørensen SS,Hansen M.Green tea or rosemary extract added to foods reduces nonheme-iron absorption.Am J Clin Nutr.2001;73:607–12.10.Tuntawiroon M,Sritongkul N,Brune M,Rossander-Hulten L,Suwanik R,Hallberg L.Dose dependent inhibitory effect of phenolic compounds in food on nonheme iron absorption in man.Am J Clin Nutr.1991;53:554–7.mpe JW.Spicing up a vegetarian diet:chemopreventive effects ofphytochemicals.Am J Clin Nutr.2003;78:579S–83S.12.Eigner D,Scholz D.Ferula asa-foetida and Curcuma longa in traditionalmedical treatment and diet in Nepal.J Ethnopharmacol.1999;67:1–6.13.The National Identity Office,Office of the Prime Minister.In:Thai herbsand herbal products.Bangkok,Thailand:Srimuang Printing;2004. 14.Brune M,Hallberg L,Skanberg AB.Determination of iron-bindingphenolic groups in foods.J Food Sci.1991;56:128–31.15.Miean KH,Mohamed S.Flavonoid(myricetin,quercetin,kaempferol,luteolin,and apigenin)content of edible tropical plants.J Agric Food Chem.2001;49:3106–12.16.Materska M,Perucka I.Antioxidant activity of the main phenoliccompounds isolated from hot pepper fruit(Capsicum annuum L.).J Agric Food Chem.2005;53:1750–6.17.Limlomwongse L,Chaitauchawong C,Tongyai S.Effect of capsaicin ongastric acid secretion and mucosal bloodflow in the rat.J Nutr.1979;109:773–7.18.Vasudevan K,Vembar S,Veeraraghavan K,Haranath PS.Influence ofintragastric perfusion of aqueous spice extracts on acid secretion in anesthetized albino rats.Indian J Gastroenterol.2000;19:53–6.19.Minowa S,Tsuchiya S,Horie S,Watanabe K,Murayama T.Stimulatoryeffect of centrally injected capsaicin,an agonist of vanilloid receptors, on gastric acid secretion in rats.Eur J Pharmacol.2001;428:349–56.20.Skikne BS,Lynch SR,Cook JD.Role of gastric acid in food iron-absorption.Gastroenterology.1981;81:1068–71.21.Baum L,Ng A.Curcumin interaction with copper and iron suggestedone possible mechanism of action in Alzheimer’s disease animal models.J Alzheimers Dis.2004;6:367–77.22.Chattopadhyay I,Biswas K,Bandyopadhyay U,Banerjee R.Turmericand curcumin:Biological actions and medicinal applications.Curr Sci.2004;87:44–53.23.Bernabe´-Pineda M,Ramı´rez-Silva MT,Romero-Romo MA,Gonza´lez-Vergara E,Rojas-Herna´ndez A.Spectrophotometric and electrochem-ical determination of the formation constants of the complexes Curcumin–Fe(III)–water and Curcumin–Fe(II)–water.Spectrochim ActaA Mol Biomol Spectrosc.2004;60:1105–13.24.Borsari M,Ferrari E,Grandi R,Saladini M.Curcuminoids as potentialnew iron-chelating agents:spectroscopic,polarographic and potentio-metric study on their Fe(III)complexing ability.Inorg Chim Acta.2002;328:61–8.25.Kunchandy E.Effect of curcumin on hydroxyl radical generationthrough Fenton reaction.Int J Pharm.1989;57:173–6.26.Walczyk T,Tuntipopipat S,Zeder C,Sirichakwal P,Wasantwisut E,Hurrell RF.Iron absorption by human subjects from different iron fortification compounds added to Thaifish sauce.Eur J Clin Nutr.2005;59:668–74.27.Walczyk T.Iron isotope ratio measurements by negative thermalionization mass spectrometry.Int J Mass Spectrom Ion Processes.1997;16:1217–27.28.Walczyk T,Davidsson L,Zavaleta N,Hurrell RF.Stable isotope labelsas a tool to determine iron absorption by Peruvian school children froma breakfast meal.Fresenius’J Anal Chem.1997;359:445–9.29.Kastenmayer P,Davidsson L,Galan P,Cherouvrier F,Hercberg S,Hurrell RF.A double stable isotope technique for measuring iron absorption in infants.Br J Nutr.1994;71:411–24.30.Brown E,Hopper J Jr,Hodges JL Jr,Bradley B,Wennesland R,Yamauchi H.Red cell,plasma and blood volume in healthy women measured by radio chromium cell-labeling and hematocrit.J Clin Invest.1962;41:2182–90.31.Hosain F,Marsaglia G,Finch CA.Blood ferrokinetics in normal man.J Clin Invest.1967;49:1–9.32.AOAC.Official methods of analysis of the Association of OfficialAnalytical Chemists.In:Horwitz W.editor,17th ed.,Methods:967.22, 986.11.Washington(DC):Association of Official Analytical Chemists;2000.33.Sapers GM.Determination of ascorbic acid,dehydro-ascorbic acid andascorbic acid-2-phosphate in infiltrated apple and potato tissue by HPLC.J Chromatogr.1990;503:431–6.34.Parviainen MT,Nysso¨nen K.Vitamin C analysis.In:De Lenheer A,Lambert WE,Nelis HJ,editors.Modern chromatography analysis of vitamins.New York:Marcel Dekker;1992.p.235–260.35.Singleton VL,Rossi JAJ.Colorimetry of total phenolics with phos-phomolybdic-phosphotungstic acid reagents.Am J Enol Vitic.1965;16: 144–58.36.Pongchaiyakul C,Nguyen T,Kosulwat V,Rojroongwasinkul N,Charoenkiatkul S,Eisman JA,Rajatanavin R.Effects of physical activity and dietary calcium intake on bone mineral density and osteo-porosis risk in a rural Thai population.Osteoporos Int.2004;15: 807–13.37.Hurrell RF,Juillerat MA,Reddy MB,Lynch SR,Dassenko SA,CookJD.Soy protein,phytate,and iron absorption in humans.Am J Clin Nutr.1992;56:573–8.38.Manach C,Scalbert A,Morand C,Remesy C,Jimenez L.Polyphenols:food sources and bioavailability.Am J Clin Nutr.2004;79:727–47. 39.Prasad N,Raghavendra R,Lokesh B,Naidu K.Spice phenolics inhibithuman PMNL5-lipoxygenase.Prostaglandins Leukot Essent Fatty Acids.2004;70:521–8.40.Thampi PSS.A glimpse of the world trade in Capsicum.In:Krishna AD,editor.Capsicum:the genus Capsicum.New York:Taylor and Francis;2003.p.16–17.41.Price ML,van Scoyoc S,Butler LG.Critical evaluation of vanillinreaction as an assay for tannin in sorghum grain.J Agric Food Chem.1978;26:1214–8.42.Brune M,Rossander L,Hallberg L.Iron absorption and phenolic com-pounds:importance of different phenolic structures.Eur J Clin Nutr.1989;43:547–58.2974Tuntipopipat et al. by guest on August 9, 2013 Downloaded from。