Polybromated Biphenols Andrea Leasure BIOL 464 Andrea Leasure BIOL 464.
J. Biol. Chem. 1928 Peterson 215 23
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THE IRON CONTENT OF PLANT AND ANIMAL FOODS.*BY W. H. PETERSON AND C. A. ELVEHJEM.
(From the Department of Agricultural Chemistry, University of Wisconsin,Madison.)
(Received for publication, April 2, 1928.)As more data are accumulated it becomes ncreasingly evidentthat great variations exist in the mineral content of differentsamples of the same foodstuff. Only when a large number ofsamples rom different parts of the country have been analyzed willit be possible to approximate the probable mineral content of ourdiet. With the data now available it is difficult to draw any safeconclusion as to the adequacy or inadequacy of the supply of the
mineral elements in an average diet.In a previous paper (1) the iron content of certain tissues wasgiven. In the present paper figures will be given for the percent-age of iron in about 150 of our common food materials. Most ofthese analyses are of plant materials, but figures for a number ofsamples of fish and poultry are also included. Included in theaverages are the data reported in two previous papers (2, 3) forthe iron content of about twenty vegetables.EXPERIMENTAL.
Preparation of Samples.-The materials used in this study werefor the most part bought in the local markets. The fruits andvegetables were carefully washed, spread out in thin layers, andleft until the water had evaporated. They were then cut insmall pieces and moisture was determined by drying to constantweight at, 100. The dried materials were ground in a glassmortar and kept in stoppered bottles until t.he time of analysis.Before a sample was taken for this purpose the material wasdried for several hours to remove any absorbed moisture.
* Published with the permission of the Director of the Wisconsin Agri-cultural Experiment Station.215
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216 Iron Content of FoodsThe cereals were partly ljroken but not dried before analysis.
The nuts were ground but not dried before the sample was taken foranalysis. This was necessary in order to avoid a change in theuniformity of the sample due to the separation of fat during thedrying. Moisture in the cereals and nuts was determined by dry-ing other ground samples to constant weight at 100.
Methods for the Determination of Iron.-The ferric thiocyanatecalorimetric method as described in Standard Methods for the
TABLE IDetaile d Data for Certain Represen tative Foods , Illustratin g Method for
Determination of Iron.
C&Et%
gm. ng. m m. Perm g. cenl Per centCereals. Wheat flour. 8 0.127.30.073 0.00091
+ 0.1 Fe.g. 8 0.1 11.60.172 99Fish. Salmon. 5 0.223.20.172 0.00344
+ 0.1 Fe.g. 5 0.2 14.8 0.270 98Fruits. Peach es. 3 0.123.40.085 0.00285
+ 0.1 Fe.g. 3 0.1 10.80.185 100Nuts. Almon ds. 4.85 0.329.30.205 0.00423
I + 0.1 Fe.g. 4.85 0.3 19.80.303 98Vegetables. Potatoes. 5 0.2 20.7 0.193 0.00386
+ 0.1 Fe.g. 5 0.213.40.298 105Head lettuce. 1 0.1 15.90.126 0.01260
+O.lmg.Fe. 1 0.1 8.90.225 99* Standard set at 20 mm.
Examination of Water and Sewage (4) was used when the phos-phate content was not so great as to produce fading. To deter-mine whether phosphates or other compounds were interfering, allanalyses were run in triplicate and a known quantity of iron(usually 0.1 mg.) was added to one of the three samples. If arecovery of 95 per cent or more was obtained, it was assumedthat there was no interference. If a satisfactory recovery wasnot obtained, the analysis was repeated on a smaller quantity ofmaterial. The disturbing effect of phosphates seems to disappear
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W. H. Peterson and C. A. Elvehjem 217when the cluantity falls below a certain minimum. If the ironcontent was too low to permit of a reduction in the size of Dhesample, the analysis was made by the method of Elvehjem andHart (5).
In Table I are given the complete analytical data for severalrepresentative foodstuffs ranging from low to high in their ironcontent. The recovery of added iron is more than 95 per cent inevery case. The same procedure was followed with every sampleanalyzed and good recovery of added iron was obtained. For thisreason we feel that the figures reported in this paper actually ex-press the iron content of these samples.Iron Content of Foods.-In Table II are given the moistureand iron content of the samples analyzed.
The figures range from 0.00015 per cent of iron for lemon juiceto 0.0192 per cent for parsley. The figure for parsley was sosuprisingly high that another sample bought a year later wasanalyzed and was found to contain approximately the same per-centage of iron as the first sample. As a carrier of iron, spinachdoes not compare with parsley. It would be desirable to comparea number of samples of these two vegetables to see whetherparsley generally exceeds spinach in its iron content.
If the groups of foodstuffs are arranged in descending order withreference to their iron content, the following series is obtained:Three dried legume seeds, 0.0094 per cent; seven green leafyvegetables, 0.0069 per cent; seven dried fruits, 0.0054 per cent;twelve nuts, 0.0041 per cent; eighteen cereals and their products,0.0034 per cent; four kinds of poultry, 0.0014 per cent; two greenlegumes, 0.0014 per cent; fourteen roots, tubers, stalks, and bulbs,0.0011 per cent; fifteen non-leafy vegetables, 0.00085 per cent;twenty kinds of fish, 0.00083 per cent; twenty-three fresh fruits,0.00066 per cent.This order results from calculations made on the basis of theundried edible product. The high rank of legumes, dried fruits,and nuts is, of course, due in large part to the low percentage ofmoisture contained in these foods. If the calculations are made onthe dry basis the leafy vegetables take the first place with morethan 6 times as much iron as the next group, the dried legumes.The green leafy vegetables are par excellence the best source of ironin the diet.
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TABLE I I .Irox Content of Foods (Calculated on Basis of Undried Material).
Food.* Moisture. Iron (Fe)..- per cent per cent3.9 0.00407lmonds .......................................Apples.Duchess............................. .........
Greening .....................................Yellow t.ransparent ...........................Snow ........................................Apricots, dried (2). ...........................Artichoke .....................................Asparagus ......................................Bananas ......................................Barley ......... .......... ...... ......... ....Beans, Kidney ................................. Lima .................................. Navy. ................................. String ..................................
Maximum. ..................................Minimum ...................................Average (7). ................................Beets. .........................................Beet greens, tops .......... ......... ..........
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W. H. Peterson and C. A. ElvehjemT ABLE II-continued.
Food.*
Chestnuts, Italian .............................Chocolate, bitter ..............................Cocoa .........................................Coconut ......................................Corn, white ...................................I yellow ..................................Corn-meal, yellow .... .... .... .... .... .... .... .Corn flakes ............ ............ ...........Cream of Wheat .............................Cucumbers. ...................................Currants (2). ........... ............ .......... dried ................................Dandelion ....................................Dates, dried ............ ............ ..........Eggplant .....................................Eggs. .........................................Egg yolk ......................................Figs, dried ....................................Fish and sea food.
Bass ........................................Bluefish .....................................Catfish ......................................Cod.. ...................................... .Flounder ....................................Haddock ....................................Halibut .....................................Herring .....................................Lake trout ..................................Lobster .....................................Mackerel. ....................................Oyster (2). ........... ............ ..........Perch .......................................Pickerel .....................................Pike. .......................................Red snapper ................................Salmon. .....................................Shad ........................................Shrimp .....................................Whitefish ...................................
Flour, Graham ...............................I patent ................................. rye .....................................
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Moisture. Iron (Fe).per cent per cent
34.5 0.004101.9 0.003154.5 0.0031339.3 0.002675.7 0.002978.5 0.002286.0 0.001306.2 0.002787.4 0.0008596.8 0.0003586.8 0.00070
32.7 0.0047488.3 0.0060427.5 0.0050792.5 0.0006171.9 0.0025249.5 0.0076038.0 0.0039677.076.780.081.780.078.867.377.679.081.177.687.580.472.580.279.275.769.870.479.8
8.96.4
0.000260.000600.000360.000340.000730.000420.000930.000590.000780.000440.000750.003140.000480.000800.000340.000400.000830.000530.002670.000420.003700.000910.00283
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220 Iron Content of FoodsTABLE II-Continued.
Food.* Moisture. Iron (Fe).
Gooseberries ...................................Grapefruit, pulp ......... .......... ......... ...Grapes, Concord.Pulp. ........................................
Skin. ........................................Grapes, Malaga ................................ red ....................................Hazelnuts ......................................Hickory nuts ......... .......... ......... .......Hominy. ......... .......... ........ . ......... ..Honey .........................................Kohlrabi (2). .......... .......... ......... .....Kumquats .....................................Lemon, juice ......... ......... .......... .......I peel ....................................Lettuce, head .......... ......... .......... .....I leaf ....................................Milk (20). .....................................Molasses .......................................Mushrooms ....................................Oatmeal (2). ...................................Oats. ..........................................Olives, green, canned ...........................Onions ......... .......... .... . .......... .......Orange, juice .......... .......... ......... ..... peel ................................... pulp (2). ......... ......... .......... ..Oyster plant ...................................Parsley (2). .......... ......... .......... .......Parsnips .......................................Peaches ........................................ dried ..................................Peanuts ........................................Pears ..........................................Peas, green (3). ................................Pecans .........................................Peppers, green .... .... .... .... .... .... .... .... . red ...................................Pineapple ......................................Pistachio nuts .......... ......... .......... ....Plums (3). ......... .......... .......... ........Pomegranate ...................................
per cent percent90.1 0.0004792.8 0.0002772.577.279.683.23.82.97.5
90.785.096.087.596.694.487.526.271.26.46.277.093.779.287.076.587.682.787.237.42.083.975.22.394.091.792.04.084.973.5
0.000740.001360.002280.000900.004500.002380.000540.001150.000680.000510.000150.000750.000420.001870.000240.007970.003140.003800.008400.002110.000300.000280.000420.000660.001240.019210.001070.000360.006060.002310.000460.001770.002580.000410.000600.000320.007920.000770.00117
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W. H. Peterson and C. A. ElvehjemTABLE ll-concluded.
Food.*
Potatoes ...................................... sweet ................................Poultry.Chicken, dark meat ......................... light ........................Duck .......................................Goose .......................................Turkey, dark meat .......................... light .......... .......... ......Prunes, dried ......... .......... .......... ....PuffedRice ...................................Puffed Wheat .................................Pumpkin ......................................Quinces .......................................Radishes (2). .................................Raisins, seeded ......... ......... .......... .... seedless ..............................Raspberries (2). ..............................Rhubarb ......................................Rice, polished .................................Rutabagas ....................................Rye. ..........................................Spinach. ......................................Squash, Hubbard .. .... .... .... .... .... .... ...I Queen ................................Strawberries (2). .... .... .... .... .... .... .... ..Sweet corn (2). ................................Tangerines, pulp ..............................Tomatoes ..................................... canned ..............................Tomato puree, canned .........................Turnips .......................................Walnuts, Black ......... .......... ......... ....I English. .............................Watercress ....................................Watermelon ...................................Wheat ........................................ bran ...................................
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Moisture. Iron (Fe).per cent per cent78.2 0.0008572.1 0.0009267.576.643.757.072.172.244.110.98.691.782.594.4
28.231.984.194.49.580.9
6.481.990.481.190.381.786.094.2
91.52.03.392.592.77.63.4
0.001010.000700.001710.002020.002040.001030.005170.001070.004100.001100.001010.001360.006990.00413o.ooo990.000860.001050.001070.003700.006600.000550.000390.000660.000510.000610.000600.001300.002200.000700.005980.002140.007210.000230.003720.00852
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222 Iron Content of FoodsAttention is called to the low percentage of iron in cabbage,
celery, and head lettuce as compared with the green leafy vege-tables. A direct relation between iron content and presence ofchlorophyll is evident. From the point of view of its iron contentit is unfortunate that head lettuce is chosen by the public generallyin preference to the superior leaf lettuce.
That soil and climatic conditions largely determine the ironcontent of the plant is shown by the great variations which existin different samples of the same plant material; for example, apples,string beans, and cabbage. One sample may contain 2 or 3 timesas much iron as another sample of the same product.
In a previous publication (1) it was noted that beef juice con-tained only a small percentage of the total iron in the original beef.The same tendency of iron t,o cling to the solid part of the materialis observed in the case of orange juice and pulp. When orangejuice was pressed out and strained as is the practice in preparingthis material for feeding infants, only about 25 per cent of thetotal iron was obtained although more than 60 per cent of theweight of the orange pulp was represented by the expressed juice.Tomato juice similarily prepared contained about 38 per cent ofthe iron in the original vegetable. These facts indicate the de-sirability of feeding infants both juice and pulp as early as pos-sible in order to take full advantage of the iron content of thesematerials.
An interesting condition was found to exist in the iron content ofvarious kinds of fish. Salt water fish contained about 40 per cent,more iron than the fresh water species. Fish with dark-coloredtissue contained about 75 per cent more iron than those havinglight-colored tissue. The higher iron content of the dark-coloredtissues was encountered in both the salt and the fresh water species.If the figures for the different groups of foods are compared withthe figures for the same materials given by Sherman (6), it will befound that the averages are about the same for cereals, nuts, andfish. For the most important sources of iron, the fruits and vege-tables, our results are in most instances higher. The average for62 fruits and vegetables is about 80 per cent higher than thefigures given by Sherman. It is to be expected that individualsamples would differ greatly but it does not seem reasonable thatthe average for a large number of samples should exhibit suchdifferences. We are inclined to believe that Shermans figures
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W. H. Peterson and C. A. Elvehjem 223are too low as they are compiled from different sources and are, asSherman himself says, of a ll degrees of probable reliability.The need of more analytical data on the mineral content of ourfoods is strongly emphasized by these differences.
SUMMARY.The iron content of about 150 samples of our common food
materials has been determined. The figures range from 0.00015per cent for lemon juice to 0.0192 per cent for parsley. Arrangedin descending order with reference to their iron content the classesof foods come as follows: dried legumes, green leafy vegetables,dried fruits, nuts, cereals, poultry, green legumes, roots and tubers,non-leafy vegetables, fish, and fruits.
Different samples of the same food material show great varia-tions in their iron content. For example twenty samples of cab-bage varied from 0.00017 per cent of iron to 0.00059 per cent.Vegetables containing but little chlorophyll, cabbage, celery,and head lettuce, were found to be low in iron.
The juice of oranges and tomatoes contains less of the totaliron than is proportional to the weight of expressed juice; the ironclings to the solids.Salt water fish contain more iron than fresh water fish. Fishwith dark-colored tissue contain more iron than those with light-colored tissue. The dark meat of poultry is likewise higher iniron than the light meat.
The authors wish to acknowledge the assistance of GenevieveBell, Pauline Dexter, Dorothy Ebbott, Ruth Marks, DorotheaRickaby, and Frances Roberts in the preparation and analysis ofthe samples.
BIBLIOGRAPHY.1. Elvehjem, C. A., and Peterson, W. H., J. Biol. Chem., 1927, Ixxiv, 433.2. Peterson, W. H., and Hoppert, C. A., J. Home Econom ., 1925, xvii, 265.3. Peterson, W. H., Elvehjem, C. A., and Jamison, L. A., Soil SC., 1925,
xx, 451.4. Standard methods for the examination of water and sewage, AmericanPublic Health Association, New York, 6th edition, 1925, 46.5. Elvehjem, C. A., andHart, E. B., J. Biol. Chem., 1926, lxvii, 43.6. Sherman, H. C., Chemistry of food and nutrition, New York, 3rdedition, 1926,573-597.
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