From: taltar@beaufort.sfu.ca (Ted Altar) Newsgroups: rec.food.veg Subject: Iron and Vegetarians Date: 8 Jul 94 10:30:26 GMT Organization: Simon Fraser University Lines: 1031 Message-ID: NNTP-Posting-Host: beaufort.sfu.ca THE WEIGHTY TOPIC OF IRON Ted Altar This article contains the following sections: 1: Introduction 2: RDA's 3: Heme vs Non-Heme Iron 4: Losses Between The Sexes 5: Anemia 6: Def. Of Iron Deficiency 7: Vegetarians Vs Omnivores 8: Avoid Strict Adherance To A Macrobiotic Diet 9: Absorbing Absorption Facts 10: Concl. & Practical Advice 1. INTRODUCTION The topic of iron is one of the most complex and confusing issues in nutrition for BOTH vegetarians and omnivores. You will frequently hear that iron from meat (non-heme iron) is the best source which might lead one to hastily conclude that omnivores would tend to suffer from less iron anemia than vegetarians. This, apparently, is not the case. You will also have heard that iron anemia (particularly among women) is quite possibly one of the most widespread nutritional problems in world. It is a real problem for women although there does occur some some exaggeration about how prevalent a problem it really is, due to uncertainty as to how to define "iron deficiency". Low iron stores don't constitute iron deficiency, but some studies predicate its conclusions about prevalence on such measures. It also turns out, that whatever the risk might be, it is about the same for both omnivore and vegetarians. It is not clear that vegetarians are at a greater risk. Also, depending on the assessment model used, the number of people indicated to have a deficient iron status is only ranging from 1% to 6% of the total population (of course, sub-populations like teenagers who dietary habits are terrible do have a higher incidence rate). The average human male body only contains a mere 4 grams of iron and the female body about 3 grams. That is the amount of iron one finds in a small nail! As you know, the body works to maintain a steady state so that if one consumes more sulfur, phosophorus, calcium, zinc, and so on, one must excrete that same amount of sulfur, phosophorus, etc., unless one grows in size. Curiously, this is NOT the case with iron. THERE IS NO KNOWN METABOLIC MECHANISM FOR THE EXCRETION OF IRON. How much iron do we lose each day? About 1 mg via urine, feces, sweat, sluffed skin cells, etc. How much is 1 mg? Cut up a postage stamp into 50 pieces and one of those small pieces weights 1 mg! Due to menstrual blood flow, woman lose on average half as much more (1.5mg). During typical menstrual period the iron lost is about 15 mg, which averages out over the full month to be only .5 mg per day (in about 5% of normal woman the menstrual loss can be more than 15 mg). The good news is that as menstrual losses deplete iron stores the bodily absorption of iron increases. Hey, the body is not stupid. 2. RECOMMENDED DAILY ALLOWANCES In order to maintain one's iron status males need only absorb 1 mg of iron per day and fertile females need about an extra .5 mg. Not all of the dietary iron one consumes, however, is absorbed. Hence we must eat more iron than we actually need. Amer. RDA for Iron AGE IN YEARS (mg/daily) Males 0-.5 6 mg .5 - 10 10 11-18 12 19 - 50+ 10 Females 0-.5 6 mg .5 - 10 10 11 - 50+ 15 51+ 10 pregnant 30 lactating 15 According to the RDA, 10th edition: "From the available data, it seems reasonable to conclude that a daily intake of 10 to 11 mg of iron form typical U.S. diets is sufficient for most women. Those with high menstrual losses appear to compensate for those losses by improved absorption of dietary iron, since the prevalence of iron deficiency anemia in that group is quite low." [p. 200] If 10 to 11 mgs of iron is sufficient for most woman, then why is the American RDA 15 mg/day of iron? The reason is simply to ensure that not only most women (at least 86% of women between 15 to 44 years), but practially all women (at least 95%) are meeting their needs for iron, the American RDA's guidelines therefore suggest 15 mg/day as seen above. We should remember that RDA's are not written in stone but are guidelines that change over time (recommended amounts of iron were actually lowered in the most recent American guidelines) and vary between countries. For example: Canadian guidelines: AGE RDA for Iron 0-4mos .26 5-12mos 7.0 1-5 years 6 6-11 8 12-15 females 13 " " males 10 16-18 females 12 " " males 10 19+ females 13 males 9 Post-menopausal 8 65+ 8 Roughly, the British RDAs for iron, however, are 6-12 mg for children and adolescents, 10 mg for men and 10-12 mg for women. Thus, RDA's are not written absolutes, but are guidelines that will vary for particular populations. That is why the WHO (World Health Organization) are really more suitable for vegetarians since their guideline are bases upon a much larger world populations of people who do eat a lot less meat than Americans, Canadians or the British. Now, please do not go mindless trying to assess your iron status by calculating how much iron is in your foods according to some tables and than seeing if you meet precisely the RDA's. Even if you are slightly below, there is no cause for alarm, nor if you are above is there reason for complete complacency. A number of factors enter in to make this issue more complex, the least of which you must also take into account are the factors affecting ABSORPTION and the risk of iron overdoses via supplementation or too much liver. More of this latter. For now, consider the following warning by a noted researcher on dietary iron (Emery, 1991): Possibly, as discussed in the previous chapters, while decreasing the risk of classical iron-deficiency symptoms, the current RDA for iron is increasing the risk of infection. In this respect, nutritionists have lowered their RDAs for iron over the past decade -- 40% lower in newborn infants and 17% lower in adult females in 1989 as compared to 1980. Certainly, the physiology of these groups has not changed, which leads one to wonder about the accuracy of these values. Nutritionists may correctly respond that values in chemical tables have also been subject to change. Even atomic weights of the elements are revised from time to time. Nevertheless, the fundamental difference is that the latter values are merely reported, not recommended. No value judgment is placed on reported atomic weights. One should be far more cautious in giving recommendations than in reporting measured values, especially to unaware lay people whose health is at stake. The use of the word "recommend" is misleading. I foresee a continuing downward trend of RDAs for iron and an upward trend for Vitamin C as more hard data become available. [p. 102 -3] To illustrate how really easy it is to obtain sufficient iron from a vegetarian diet, consider the following examples of 2 kinds of diets, diets that don't even include high iron foods like nutritional yeast or blackstrap molasses. Diet #2 is more typical of our sensible vegetarian while diet #1 is an example of a less discerning vegetarian. ****************************************************************** IRON FROM TWO VEGETARIAN DIETS Over one day, average 2000 Kcal, iron in mg, all numbers from NLK: (nonUS flour is assumed to be unfortified with iron): Diet #1, US Kcal/Iron nonUS Diet #1 non US Diet #2 Kcal/Iron KCal/Iron White bread(3) 200/2.5 200/0.6 WW bread 200/2.1 Peanut butter 100/0.4 100/0.4 Oats 150/1.6 Jam 100/0.5 100/0.5 soymilk 50/1.2 1 ornge, 1 appl 150/0.4 150/0.4 1 cantalp 150/0.5 White rice 200/1.5 200/0.5 brwnrice 200/1.5 tomto-lttc(2srv) 30/1.0 30/1.0 chard 60/6.4 fruits 150/0.4 150/0.4 150/0.4 Pasta 400/5.0 400/1.5 quinoa 400/9.0 Potatoes 300/2.4 300/2.4 beans 400/11.0 carrt sld 30/1.0 30/1.0 broccoli 70/2.7 fruits 150/0.4 150/0.4 150/0.4 almonds 100/0.8 100/0 - oilve oil 100/0 100/0 100/0 Total 2010/17.3 2010/9.3 2080/36.8 [table provided by Giovanni Bonvicini] *********************************************************************** 37mg, even at low absorption (5%), will be more than enough iron for any healthy individual requiring 1mg/100Kcal of iron daily. All three diets meet the RDA's for males and non-pregnant/lactating females. It is to be noted that the above calculations don't even include the factor of enhanced iron absorption from such things as the vitamin C from fruits, use of vinegar, cooking in iron pots, etc. From the above table, one can also see how important it is to eat whole foods and not waste time and money on such over-refined foods as white flour. 3. WHAT SO GREAT ABOUT HEME IRON? HEME IRON is the iron that comes from meat, but only 1/3 of the iron in animal tissue, beef or poultry is heme iron as such. The bulk is still NON-HEME IRON, the same kind of one gets from plants. The world's supply of dietary iron is thus predominantly in the form of non-heme iron. Even for omnivores, only about 5% to 10% of the total dietary intake is heme iron. Since its absorption can around five to tenfold higher than nonheme iron, heme iron may *in theory* supply as much as 1/3 of the daily iron requirement for omnivores. Thus, even for omnivores the bulk of their iron is of the non- heme variety. The absorption of non-heme iron, therefore, really deserves a greater emphasis in everyone's attention to dietary iron. Why then, this praise for the heme iron of meat? Again, the apparent advantage of heme iron is that it is more readily absorbed. Depending on one's iron stores, the absorption heme iron is on average from 15% to 35%. Nonheme iron is less well absorbed (on average it ranges from about 2% to 20%), but it's specific rate of absorption is highly responsive to the amount of one's current iron store. The lower the stores, the greater the absorption. Nonheme iron absorption rates is also more readily influenced by what else has been eaten along with it, which can serve to increase or decrease absorption, as shall be mentioned later. A possible disadvantage of heme iron is that it's variable absorption is less affected by the amount of iron consumed or the by iron status of the individual. One can more readily absorb too much heme iron than non-heme iron, should one's intake of iron already be excessive. Chronic low levels of too much iron can both be a health problem. A recent prospective cohort study of some 2,000 Finish men (between ages 42 and 60) during a 5 year period, resulted in the second strongest predictor of heart attacks (51 men had heart attacks during that 5 year period), after smoking, turned out to be blood levels of ferritin (a storage form of bodily iron), which is a good indicator of overall iron levels. For each 1% increase of blood ferritin, there was more than a 4% increase in heart-attack risk. A ferritin level of 200 or more, compared with the normal 100 to 150 level, doubled the risk (see the 1992 September issue of CIRCULATION) 4. TOLERATED LOSSES OF IRON BETWEEN THE SEXES Adult males lose 1 mg of iron daily, two thirds of this as desquamated epithelium and secretions from the gut while most of the other one third is loss in urine and skin growth. In people with low iron status, the body attempts to conserve its iron so that only about .5 mg is lost daily. Iron stores in males are about 900-1000 mg. During the childbearing years adult females lose about 1.5 mg daily as averaged over the month. The additional 15 mg per month (ranges, 3-80) comes from menstrual bleeding. With pregnancy the total loss of additional iron is about 800 mg. In the adult female approx. 300 mg are stored. This lower storage is due to the lower intake and greater losses of iron. Bezkorovainy (1980) reports that various surveys have shown that 10-30% of adult woman have no measurable iron reserves even in countries with iron fortification programs. Such a condition alone, however, is not full-blown iron deficiency. During the later stages of pregnancy, the absorbability of dietary iron also increases. The normal omnivore or vegetarian diet would seem provide sufficient total iron to more than replace losses. Of course, not of that dietary iron is absorbed but absorbability is, as we have seen, quite variable and is dependent on bodily need and such things as the presence of vitamin C in the diet . Since the average diet contains 6 mg of iron per 1000 kcal, adult males should be able to obtain a positive balance with an absorption rate of only 5% of what is consumed. This absorption will increase up to 20% in iron deficient individuals, hence men can tolerate losses of approximately 3.5 mg daily without becoming progressively anemic. In woman, the balance however is more difficult to maintain due to an increased iron loss through menstruation. The average woman consumes about 10-12 mg of iron daily and its their absorption being on about 12-15%, woman can therefore only tolerate about a 2 mg daily loss of iron. 5. IRON ANEMIA With a severe anemia the oxygen transport of the blood is compromised and one's ability to exert oneself physically would also be impaired. Fatigue and loss of stamina can also be due or compounded by a cellular enzyme dysfunction. Less severe depletion has been thought to include also irritability, lassitude, impaired performance on certain cognitive tasks (particularly for children), an altered catecholamin metabolism or a lowered body temperature (Hunt & Groff, 1991). The most frequent cause of iron-deficiency anemia in males is chronic bleeding, usually from the GI tract. Ulcer sufferers take note. For women it is pregnancy In general, four populations are particularly at thought to be at a higher risk for inadequate dietary iron intake: 1. infants & young children (6 mos. to 4 years) due to low iron content of milk and other preferred foods, rapid growth rate, and small reserves. 2. adolescents in their early growth spurt because of rapid growth and needs of expanding red-cell mass 3. females during childbearing years because of menstrual iron losses 4. pregnant woman because of their expanding blood volume, demands of fetus and placenta, plus blood losses to be incurred in childbirth. There are different assessement models for determining iron status and there is some debate about whether the models using the more convenient blood assays are sufficiently precise and reliable for most purposes. According to the Second National Health and Nutrition Examination Survey (NHANES II) of the U.S. population (1976 - 1980), the prevalence of impaired iron status ranged as follows: RANGE OF IRON DEFICIENCY IN FEMALES DEPENDING ON ASSESSMENT MODEL USED Age % of Woman 11 - 14yr 2.7 - 6.1 15 - 19 2.5 - 14.2 20 - 44 4.0 - 9.6 45 - 64 3.8 - 4.8 65 - 74 2.7 - 3.2 6. DEFINITION OF IRON DEFICIENCY Some of you may wish to skip this section, as here we introduce some technical terms. The short and fast of this discussion is that there really, according to the RDA, 10th edition, "currently there is no single biochemical indicator available to reliably assess iron status in the general population" There different stages of iron deficiency and there are different ways to differentiate these stages. The follow differentiation (Scimshaw, 1991), is as good as any and will serve our purpose: stage 1: Stored iron is depleted, a process reflected in declining levels of ferritin. stage 2: Next, levels of serum iron plummet, and as a result the iron transport protein, transferrin, is no longer fully saturated. At this second stage, cellular compounds requiring iron begin to be affected. stage 3: As the deficiency persists, synthesis of hemoglobin is inhibited, and anemia develops. This last stage is characterized by reduced numbers of now small, pale blood cells. There are 3 common approaches or means of measuring iron deficiency that are most commonly used: 1. Serum ferritin model. Abnormal levels must be found in two of the following blood indicators: Serum ferritin, transferrim saturation and erythrocyte protoporphyrin 2. Mean cell volume. Same as above except mean cell volume is substituted for serrum ferritin 3. Mean cell Hemoglobin. Defined as the corpuscular hemoglobin levels. The normal range is The World Health Organization has "operationally defined" iron anemia in terms of hemoglobin levels: hemoglobin (g/dl) males over 14 < 13 females over 14 < 12 pregnant woman < 11 1st trimester " " < 10.5 2nd " " " < 11 3rd " Range for normal hemoglobin levels is quite broad: normal hemoglobin range (g/dl) men 13 - 16 women 12 - 16 Also, the actual deficit of hemoglobin may vary considerably among those below these provisional cut-offs. It is generally thought that haemoglobin levels (amount of a iron-bound oxygen carrier protein in the blood) is one of the best ways to indicate iron status and the likelihood of anemia being present (Victor Herbert, 1987). The BMA (Brit. Medical Association), however, stated in 1986 that haemoglobin levels as low as 11 g/l are NOT significant to health and that the importance of maintaining haemoglobin at the previously recommended high levels has been exaggerated. [see DIET, NUTRITION & HEALTH, London: BMA, 1986.] T It is important to keep in mind that the ability to absorb dietary non-heme iron is sensitive to the iron status of the body (this is differential absorption does not occur to nearly the same extent with the heme iron from meat). As stores are reduced, absorption is greatly increased. Now, reduced stores is not full blown iron deficiency anemia. Far from it, as indicated by Simshaw's 3 stage model above. Just for interest, here are some other models of various stages or iron deficiency and how they are measured. According to Bezkorovaniy (1980), in the development of iron deficiency and finally iron deficiency anemia proper, we have the following progression: stage clinical measure Mildly decreased - bone marrow smear iron stores Moderate to severe - increased absorption reduction of stores - decreased serum iron ferritin - decreased % transferrin saturation Iron deficiency - decreased serum iron - increased TIBC Iron Deficiency Anemia - decreased hemoglobin - decreased hematocrit Sorry for the technical details about the clinical measures of when a certain stage has been reached, but these terms are important as we look as some research on this topic. Here are some definitions: transferrin is a transfer and storage molecule of iron that has been converted to ferric state and complexed with protein like apoferritin that acts as a shell to trap the iron. Hematocrit is a measure of the percentage of cell volume to the volume of whole blood hemoglobin is content of hemoglobin (the oxygen carrier protein) in the blood mean corpuscular volume is the average cell volume. According to the RDA, 10th edition, there are 3 stages of "impaired iron status" (note that we are not yet talking about "iron deficiency" until we reach the 3rd stage): stage 1: - plasma ferritin < 12 ug/liter - no functional impairment stage 2: - red cell protoporhyrin levels elevated - transferrin saturation reduced to < 16% - work capacity performance may be impaired stage 3: - iron deficiency anemia - total blood hemoglobin levels are reduced below normal values - severe anemia characterized by small red blood cells (microcytosis) with low hemoglobin concentrations (hypochromia). So, if one is worried about iron anemia, one must go and get a blood test and keep in mind that there are degrees of "deficiency". The blood test that gives the earliest warning signs for an impending iron deficiency status is that of serum ferritin: TEST FOR ADULT IRON STORE STATUS SERUM FERRITIN (ug/L = ng/dL = mg/dl): reference range males 16 - 300 females 4 - 161 (from Tierney, et al., "Current Medical Diagnosis & Treatment, 1994) reference range borderline males 20 -300 10 - 20 females 20 - 120 10 - 20 (from J. Wallach, "Interpretation of Diagnostic Tests, 1992) Low ferritin levels do not necessarily indicate a current iron deficiency although they do provide an index (not perfect) of one's current iron store status. How low is too low is still an area of uncertainty and this in part accounts for there being different reference ranges in different test interpretation manuals. Some manuals consider levels below 12 as indicating a high probability of a current or impending iron-deficiency anemia. To err on the side of caution, one can take the more conservative cutoff by Wallach and consider levels below 20 as too low. Remember, however, that informed judgement for the one's individual circumstances should also be part of interpreting a ferritin test result. Vegetarians will, as we shall in the next section, have lower levels than omnivores but on average will be within the normal range. 7. VEGETARIANS VS OMNIVORES Now, it is often said that vegetarians are at greater risk of iron anemia than omnivores. Is this true? Calculations of iron intake sufficiency/insufficiency have been undertaken. Consider that following results from a sample of 97 omniovores, fish eaters and vegetarians: Percentage of Participants whose Iron intakes met or *exceeded* 100% of the 1974 American RDA's. % females % males omnivores 4 88 fish eaters 36 88 vegetarians 46 87 [from Taber & Cook, 1980) Of course, we have to remember that the 174 American RDA's for iron were higher than the more recent recommendations (at that time it was 18 mg for all adult, fertile woman and 10 all adult males. No wonder the males were doing better by this now dated criterion). Two things to note of import: First, potential iron deficiencies (as suggested by a percentages of less than 100% meeting or exceeding RDA levels) are a problem with BOTH omnivores and vegetarians but vegetarian women are doing better than meat-eating woman. Vegetarian men and meat-eating men are doing equally well. Second, the problem is most particularly a problem among WOMEN. We have here a nasty sex difference where again women are getting the short end of the "stick". Among males, there are no differences between diets, but there is a dietary difference among females. More recently, a study of vegetarians in Israel (Levin et al., 1986) found their blood levels of iron and zinc to be normal, although their diets contained twice as much fiber (phytate is thought to inhibit iron absorption) as a matched meat-eating control group (this was also true for other minerals here studied, namely calcium, phosphorus and magnesium). A Canadian study of 56 middle-aged vegetarian women actually found their blood levels of iron and zinc to be HIGHER than those of meat-eating women (Anderson et al., 1981). Only a few of these women took supplements and those who did interestingly had no higher blood mineral levels than those who didn't. An 1988 American study (Worthington-Roberts et al., '88) looked at the iron status of those who ate: (1) red meat (2) poultry and fish but no red meat (3) lacto-ovovegetarians The red meat eaters had a better iron status than the lacto- ovovegetarians (as indicate below, milk and eggs actually inhibits iron absorption). But interestingly the lacto- ovovegetarians had a BETTER iron status than the woman who ate chicken and fish. The researchers speculated that the fish oils may have increased their bleeding tendency and hence their iron loss. However, not all vegetarians are equal. Consider now the results of some studies on VEGANS, who do seem to eat better than lacto- ovovegetarians. It turns out that vegan adults, in point of fact, actually have a high dietary iron take, generally more than TWICE the recommended RDA amount. Studies of British vegans showed: Daily Dietary Iron Intakes vegans omivores Study iron intake iron intake (mg/daily) Carlson et al., 1985 22.4 15.4 Rana & Sanders, 1986 31.0 14 Sanders & Key, 1987 20.5 15 Remember, British RDA for dietary intake of iron is 10 mg/daily for men and 10-12 mg for women. A survey of British vegan children (1 - 4 years) found a mean intake of iron of 10 mg a day (mainly from wheat and pulses), which exceeds by nearly half again the British RDA. [J. HUM. NUTR., '81, 35:349] Consider the following table of the iron nutritional status status of one sample of Seventh Day Adventists. Iron Nutritional Status of Omnivore and Vegetarian Students Eating a Lacto-Ovo-Vegetarian Food Service Diet (Self- Selected). omnivores vegetarians # of Participants 13 15 Serum iron (ug/dl) 121 124 Serum ferritin (mg/ml) 36.48 24.84 Hemoglobin (g/dl) 14.05 13.95 hematocrit (%) 42.04 41.67 Iron intake (mg/day) 10.36 10.60 Ascorbic acid (mg/day) 95.6 125 [from Kies & McEndree,1982] All levels are within the normal range. Serum ferritin levels for vegetarians are lower than omnivores, suggesting that vegetarian students might have lower iron stores. Levels are still within the normal range and higher ferritin levels are associated with an increased risk for CHD (1992 Finish study mentioned earlier) and cancer (Selby & Friedman, '88; Weinberg '81; Stevens et al., '88).. Now, let's take a look at the results from a more rigorously controlled dietary experiment were vegetarians were paired with omnivores so as to be matched by age, sex, size, weight and ethnic background. Both the lacto-ovovegetarians and omnivores were put on an experimentally controlled vegetarian diet for 21 to 28 days. meat-eaters lacto-ovovegetarians # of subjects 12 12 serum iron (ug/dl) 94 95 iron binding capacity (ug/dl) 312 342 hemoglobin (g/dl) 13.7 13.6 hematocrit (%) 42.3 42.1 dietary iron (mg/day) 23.8 23.4 fecal iron (mg/day) 21.8 20.2 iron recovery from feces (%) 93.2 86.3 [from Kies & McEndree, 1982) Iron status were significantly different between the 2 groups, but note that vegetarians show a HIGHER iron binding capacity in comparison to omnivore subjects. This shows that vegetarians have an increased absorption capacity for iron. Thus the fecal excretion of iron was there showing a tendency to be less for vegetarians than for omnivores. So, even if omnivores do eat more dietary iron, vegetarians compensate by their ability to absorb it better from the vegetarian diet that both the omnivores and vegetarians were given. The authors concluded: As diets become more plant product orientated and less animal product oriented several factors theoretically should contribute to a decrease in iron nutritional status, particularly, in vulnerable groups such as young women. However, it appears that host adaptive mechanisms come into play which enable individuals consuming plant orientated diets to make better use of these poor iron availability resources than would be expected. One of the commonly used, and indexes to current iron status with respect to current stores is that of a serum ferritin test. This appears to be the only index of iron status on which lacto-ovovegetarians are score lower than omnivores. But maybe we should keep in mind that serum ferritin is not perfectly correlated with actual iron stores (ferritin and hemosiderin are found in tissue and only a minute amount of ferritin is floating in the serum) nor is it the most precise or direct or reliable measure of iron storage status. It is quite possible that the iron stores of vegetarians are greater than what the serum ferritin measures would by themselves indicate. Again, there is a large individual variability in serum ferritin levels that is perfectly normal and the average lacto-ovovegetarian's serum ferritin level does in fact reside in that normal range. To briefly summarize the data on serum ferritin levels, we have: SUMMARY OF STUDIES RECORDING SERUM FERRITIN LEVELS IN LACTO-OVOVEGETARIAN FEMALES (n) meat eaters (n) vegetarians (ng/ml) (ng/ml) Worthingon- '88 (16) 29 (20) 21 McEndree et al., '83 (9) 41 (13) 23 Kies & McEndree, '82 (13) 36 (15) 25 ==== ==== weighted average 34 23 SERUM FERRITIN TEST NORMS: reference range borderline males 20 -300 10 - 20 females 20 - 120 10 - 20 (from J. Wallach, "Interpretation of Diagnostic Tests, 1992) There is certainly no evidence that lacto-ovovegetarians are suffering from a greater incidence of iron anemia than are omnivores (hemoglobin levels are normal -- see below). But we do have evidence that lacto-ovovegetarian woman have lower serum ferritin levels than omnivores. Caution should be exerted in claiming this to also be the case with vegans, although the Kies & McEndree study cited earlier did show that its sample of subjects eating a prepared vegan diet to have serrum ferritin levels of 25ng/ml. It turns out that longstanding real-world vegans consume substantially more iron and vitamin C than lacto-ovovegetarians and they don't have the problems of consuming milk and egg yolks which do inhibit the absorption or dietary iron. Unforturnately, I could find no data on the serum ferritin levels of free-living vegans. 8. AVOID STRICT ADHERANCE TO A MACROBIOTIC DIET We should keep in mind that there is a diversity of vegetarian diets and certain groups of so called "vegetarians" should not presume that the favourable nutritional status of most other vegetarian groups will apply to them. In particular, macrobiotic "vegetarians" should be considered separately and not be confused with a sensible vegetarian diet. In fact, marcrobiotic diets are not even really vegetarian, yet it is often grouped as a vegetarian diet. Studies using macrobiotic "vegetarian" infants and children, however, have not always shown them to be getting adequate iron A dietary assessment study (van Staveren et al., 1985) indicated that this might be a problem, but Dangelie et al. (1989) more recently showed that blood test measures of iron inadequacy to be present in 15% of the marcrobiotic infants. This is one so- called "vegetarian" diet to advoid, especially for infants and children. The same may also be occurring with the adults on a macrobiotic "vegetarian" diet. In one study of 50 macrobiotic "vegetarians" young adults, it was shown that their diet of grains interspersed with vegetables, fish, cheese and eggs were limiting in energy, calcium, riboflavin and for the women, iron (Brown & Bergan, 1975). These studies, unfortunately did not undertake to assess iron status via blood tests but only from dietary records. 9. ABSORBING ABSORPTION FACTS People who use food nutrient charts to try to determine if they are meeting RDA's of iron or not should be cautioned that the actual percent of iron absorption is not simply dependent upon the total amount of iron provided by the diet. Again, biological need can increase absorbability by fourfold and decrease loss to 1/3. There are also important interactions occur between foodstuffs affecting the absorption of the available iron in the diet. The most important is VITAMIN C (ascorbic acid). It turns out that vitamin C is a very powerful enhancer for the absorption of non-heme iron. The differences of absorption between heme and non-heme iron narrows when we consider that non-heme iron is often accompanied by the concomitant ingestion of vitamin C, especially by vegetarians who consume more foodstuffs with vitamin C. Surveys of vegan diets show them to have average 45% MORE vitamin C than those consuming an omnivore diet. Indeed, there have been no reports of C deficiency among vegans. range(mg/daily) average (mg/daily) vegans 137 - 210 162 ominovres 78 - 153 mg/daily 112 [from Carlson et al, 1985 See als Sanders & Key, 1987;Rana & Sanders, 1986] As one iron researcher (Monsen, 1982) concluded: It may be that the most useful and readily found therapy for iron deficiency will be dietary ascorbic acid which has the capability of increasing the rate of nonheme iron absorption several fold" Also, with respect to vegetarians depending upon non-heme iron, we have to keep in mind that absorption for this variety is dramatically increased by the presence of vitamin C. Hence, by adding simply 60 mg of vitamin C to a meal of rice, one more than triples the absorption of iron. To take another example, by simply having, say, an equivalent amount of papaya to one's eating some corn, the iron absorbed from that corn is increased fivefold. Thus, dark leafy vegetables are a good source of iron when we also consider that they are also rich sources of vitamin C. A "high availability diet would be one containing 75 mg of vitamin C. A medium availability meal would be one containing 25 to 75 mg of vitamin C. Taking more than 75 mg at any one meal does not increase any further the absorption of iron. Critric acid also independently increased the absorption of non- heme iron. Finally, dairy products and products containing tannins appear to block iron absorption. This may explain in part why vegan women seem to have a better iron status than lacto-vegetarian women. Here are some more factors (Bezkorovainy, 1980) to qualify any simplistic view that view about liver, for instance, being the world's single best source of iron: 1. "as the level of iron in the diet increases, the proportion of iron that is absorbed decreases; however, the absolute amount increases." (p. 93) 2. Switching "from a low- to a high-iron diet reduces absorption, and from a high- to a low iron diet increases absorption" 3. "Animal sources, because of their high heme content and possibly other factors, are generally, but NOT ALWAYS, better utilized than plant sources" (p. 94). [the following are from Hunt & Groff, 1990] 4. Fructose enhances iron absorption, sucrose and starch have no effect, glucose reduces absorption and iron stores the in liver and spleen. (hence fruit or fruit juices improve absorption both because of the vitamin C they provide as well as the fructose content).; 5. dairy products (milk or cheese) & egg yolk decrease absorption. (e.g., the phosphoprotein of egg yolk binds iron and prevents its utilization) 6. Of the vegetable sources, the best absorption is from soybeans (either with iron in the soybean or outside the soybean) 7. Tannins (as found in tea) reduce non-heme iron absorption to about 1/3 8. Other factors that decrease absorption include: coffee most (but not all) phytates EDTA (used as a preservative in a number of foods) phosvitin in egg yolks calcium phosphate salts (strongly chelates with the iron making it insoluable) excess intestinal alkali too rapid an intestinal transit time 10. CONCLUSIONS & REFERENCES There is no direct evidence that adult vegetarians are at a higher risk for iron deficiency than are omnivores. While iron stores may be lower, this is not iron deficiency as such. It is particularly women, and not men, who are at risk for iron deficiency. Supplements should not be seens as the first solution. Better to first ensure that one's vitamin C intakes are good and that each meal has some vitamin C from either fruits or vegetables. Obviously, everyone should eat more fruit and vegetables, which contain both iron and vitamin C. Apparently a mere 75 mg of ascorbic acid has a maximal effect on absorption of iron and amounts in excess of 75 mg apparently has no further benefit for increasing the absorption of iron (Monsen, 1982; Hunt & Groff, 1990). This amount of 75mg of vitamin C is easily obtained in a single cup of cooked kale, or a cup of strawberries, or a cup of unsweetened orange juice. Both omnivore or vegetarian pregnant and lactating women, according to the current American RDAs, would have to take supplements. Women with heavy mensural bleeding should maybe have their iron status medically assessed in order to consider their need for supplements, if necessary, during those times. Notwithstanding these exceptions, to reduce the risk for iron deficiency anemia in general, iron rich foods should be adequately represented in one's diet. For the vegetarian, such foodstuffs as whole grains, fruits, soya flour, green leafy vegetables, parsley, watercress, seeds, pulses, nuts, black molasses and edible seaweeds are rich sources. The use of iron pots and pans can contribute to dietary intake and the local water supply may also serve as an additional source depending on its iron content. As a general rule of thumb, both vegetarians and meat eaters should ensure that one's meal contains from 25 to 75 mg of vitamin C and this is not all destroy by over-cooking. Vegetarians who cook much of the ascorbate (vitamin C) out of their foods and do not eat uncooked fruits and/or lightly steamed vegetables or drink fruit juice, may require higher amounts of iron (Herbert, 1987). Again, one should not attempt to diagnosis oneself and then start taking supplements. There are hazards accompanying an excess of nutrients just as there are hazards due to nutrient deficiencies. Most nutritional problems in the West are due to excess nutrition (e.g. too much fat, calories, and possibly iron for men). For instance, an increase iron intake via supplements may reduce the absorption of zinc and therefore one has to consider zinc status as well if one is going to implement a supplemental (or even a radical dietary change) in iron intake. Best to simply get a rough idea of your iron intakes and if you think that they are really too low, adjust your diet to increase the intake of vitamin C and iron from whole foods. If one is in a high risk group and thinks that one's diet is too deficient in iron, than do consider getting a proper blood test for iron deficiency and consult a doctor or nutritionist (ideally one who is knowledgeable about vegetarianism and the differing needs and iron status of vegetarians) before self-medicating oneself with supplements. Regards, ted REFERENCES: Anderson et al. (1981). The iron and zinc status of long-term vegetarian women. AMER. J. CLIN. NUTRITION, 34:1042. Bezkorovainy, A. (1980). Biochemistry of Nonheme Iron. N.Y.: Plenum. (in particular, see the chapter written by D. Narins). Board of Science and Education, British Medical Association. DIET, NUTRITION & HEALTH, London: BMA, 1986.] T Brown & Bergan (1975), The dietary status of "new" vegetarians. AM. DIETET. ASSOC., 67:455 Carlson et al, 1985, "A comparative evaluation of vegan, vegetarian and omniovore diets", J. PLANT FOODS, 6:89; Dangelie et al., (1989). Increased risk of B-12 and iron deficiency in infants on macrobiotic diets. AMER. J. CLIN. NUTR., 1989, 50(4):818. Emery, Thomas IRON AND YOUR HEALTH: FACTS AND FALLACIES, Boston: CRC Press, 1991. Food & Nutrition Board (NRC), RECOMMMEDED DIETARY ALLOWANCES, 10th edition, Washington: National Acad. Press, 1989. Hunt & Groff (1990). ADVANCED NUTRITION AND HUMAN METABOLISM. New York: West Pub. Co. Kies & McEndree (1982). Vegetarianism and the bioavailability of iron. In Kies (ed.), NUTRITIONAL BIOAVAILABILITY OF IRON. Washington: Amer. Chemical Soc., 1982. Levin et al. (1986). Mineral intake and blood levels in vegetarians. ISRAEL J. OF MEDICAL SCIENCES, 22:105. LSRO (Life Sciences Office). 1985. Summary of a report on assessment of the iron nutritional status of the U.S. population. AMER. J. CLIN. NUTR., 42:1318 Monsen, E. (1982). Ascorbic acid: An enhancing factor in iron absorption. In Kies (ed.), NUTRITIONAL BIOAVAILABILITY OF IRON. Washington: Amer. Chemical Soc., 1982. Monsen (1982). Calculating dietary iron bioavailability: refinement and computerization. J. Am. Diet. Assoc., 80:307. Rana & Sanders, 1986, Taurine concentrations in the diet, plasma, urine and breast milk of vegans compared with omniovres, BR. J. NUTR., 56:17] Sanders & Key,1987, "Blood pressure, plasma renin activity and aldosterone concentrations in vegan and omniovre controls" HUM. NUTR.: APPL. NUTR., 41A:204; Selby & Friedman (1988). Epidemiologic evidence of an association between body iron stores and risk of cancer. INT. J. CANCER, 41:677. Stevens et al. (1988) Body iron stores and the risk of cancer. N. ENG. J. MED., 319:1047 Taber & Cook (1980), J. AM. DIETET. ASSOC., 76:21 van Staveren et al., (1985). Food consumption and height/weight status of Dutch preschool children on alternative diets. J. OF THE AMER. DIETETIC ASSOC., 85(12):1579. Victor Herbert, (1987). RDI of iron in humans", Am. J. Clin. Nutr. '87, 45:679 Weinberg (1981). Iron and neoplasia. BIOL TRACE ELM. RES., 3:55. Worthington-Roberts et al (1988). Iron status of premenopausal women in an Unversity Communty and its relationship to habitual dietary sources of protein. AMER. J. CLIN. NUTRITION, 47:275. -- Ted Altar (e-mail: taltar@sfu.ca) British Columbia, Canada