How To Absorb More Iron From Your Meals

By Michael Klaper, MD (excerpted from Lesson 7 of the Vegetarian Health Institute's Mastery Program.)

Problems With Too Little Iron

If there is a chronic shortage of iron in the body from…

  1. not eating enough iron containing foods
  2. being unable to absorb the iron in the food (from intestinal disease, chronic ingestion of absorption inhibitors, etc.) … or…
  3. iron being lost from the body

…then blood-producing cells in the bone marrow will not have enough iron to make hemoglobin for the red blood cells – and iron deficiency anemia will result.

The most common symptoms of such an anemia is a lack of physical energy (exhausted walking up a hill, etc.) but headache, irritability, and in advanced cases, shortness of breath, lightheadedness upon standing and weight loss may also occur.

Those most at risk for iron deficiency anemia:

- Menstruating women (by far, the most common group – especially women who have heavy menstrual periods.)

- Pregnant women, or those who have just given birth.

- People who are losing blood from the intestines (the most ominous cause – can be a sign of colon cancer, bleeding ulcer, etc.)

- Long distance runners (blood cells break up in soles of feet from repeated foot-strikes)

- Anyone who does not eat enough iron-containing foods, including vegan and vegetarians, or who do not absorb enough, due to consuming substances that inhibit absorption.

Problems With Too Much Iron.

More is not always better! Too much iron in the body can increase oxidation in tissues, which promote oxidation, aging, and tissue damage in the heart, liver and pancreas.[3]

There is a rare condition called hemochromatosis, where too much iron is absorbed. But a more common problem is that an individual, especially men and post-menopausal women, ingests too much iron in food and, more commonly, in supplements, and thus creates “iron overload.”[4]

This is important: Unless you have a blood-test proven iron deficiency, do not take multivitamins and other supplements that contain iron. READ THE LABEL!

Since many iron supplement tablets look like candy, iron poisoning in children is common and dangerous. Keep all iron-containing supplements out of the reach of children.

Testing For Iron Deficiency, or Excess

If there is any question of iron deficiency or anemia, your health care provider will order a Complete Blood Count (“CBC”) and measure levels of: (1)ferritin, (2)iron, and (3)carrier proteins (Total Iron Binding Capacity  -“TIBC”).

If iron deficiency is discovered, a search must be made for the cause (not eating enough in the diet, absorption problem, “silent” blood loss through heavy menstruation or GI bleeding, etc.)

Strategies to Assure Iron Adequacy.

Eat plenty of iron containing foods.

  1. These include dark leafy greens, beans, quinoa, oats, or soaked almonds or pumpkin seeds.

  2. Enhance iron absorption by employing the “iron and acid” combination.

  3. Acids include:

    1. Your own stomach acid. Avoid chronic use of “acid blockers”, like Zantac, Pepsid, etc. Occasional use is safe.
    2. Ascorbic acid (vitamin C). Squeeze lemon juice over greens, or add vitamin C foods like bell peppers, cucumbers, or celery to your iron-rich dishes.
    3. Lactic acid. Include sour kraut or fermented veggies when iron-rich greens or legumes are served.
    4. Acetic acid (vinegar). Use vinegars on salads, greens, etc.

    NOTE: The acid-containing foods should be eaten at the same time as the iron-containing foods.

  4. Reduce inhibitors of absorption.

    The most common inhibitors are phytates (a carbohydrate in whole grains and legumes,) calcium in dairy products, and polyphenols [5], [6] such as tannic acid in tea, coffee, etc.

    To reduce phytate inhibition of iron absorption:

    Soaking, sprouting, leavening and fermenting whole grains break down phytates and thus will greatly reduce phytates inhibition. [7]

    Acidic substances specifically reduce phytate inhibition [8], so adding citrus (lemon juice, orange slices, etc. for vitamin C,) vinegar, and other acids to dishes with legumes and whole grains significantly decreases inhibition of iron absorption.

    To reduce polyphenol inhibition of iron absorption (tannins and flavonoids in tea, coffee, cocoa, red wine) – avoid consuming these beverages with iron-containing foods.

    To reduce calcium inhibition of iron absorption – avoid eating dairy products with iron-containing foods.

    The effect of soy products on iron absorption is controversial. Some studies report an inhibitory effect, others do not. However, it is agreed that fermented soy products like tempeh and miso increase iron absorption. [9]

    Despite common beliefs, it appears that spinach and chard and other foods containing oxalic acid do not seem to significantly inhibit iron absorption. [10] If oxalates are a factor at all in iron bioavailability, their effects should be minimized by cooking and/or by serving the greens with acidic toppings and complements.

    All foods in the vegetarian diet, whether raw or cooked, should be chewed thoroughly to break down the cell walls. That allows maximal absorption of their minerals, including iron.

[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.

Nat Rev Gastroenterol Hepatol. 2009 Nov 17.

[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

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.

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, <60 kg body weight), recruited by poster advertizing from the staff and student populations of the ETH, University and University Hospital of Zurich, Switzerland. Thirteen subjects completed both studies. METHODS: Iron absorption was measured based on erythrocyte incorporation of (57)Fe or (58)Fe 14 days after the administration of labelled meals. In study I, test meals consisted of two wheat bread rolls (100 g) and either 150 g spinach with a native OA content of 1.27 g (reference meal) or 150 g kale with a native OA content of 0.01 g. In study II, 150 g kale given with a potassium oxalate drink to obtain a total OA content of 1.27 g was compared to the spinach meal. RESULTS: After normalization for the spinach reference meal absorption, geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P=0.86). Spinach was significantly higher in calcium and polyphenols than kale and absorption from the spinach meal was 24% lower compared to the kale meal without added OA, but the difference did not reach statistical significance (P>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.

5 Comment(s)

  1. Very good information for sure.
    Thank you.

    grace | Reply

  2. Very informative article, however, does this mean the per say consuming cereal for it's iron content, with soy milk, that the milk would interfere with the iron absorbtion? What if I had eaten an orange along with that breakfast? would that be sufficient?

    Cortney | Reply

  3. Dr. Joel Fuhrman has commented that he's had good success restoring optimal iron levels to many premenopausal women who were experiencing excessive blood loss, by the therapeutic use of  green smoothies made with spinach and some source of vitamin C containing fruit.
    He also believes that adding some fat from a small amount of nuts and seeds is very beneficial for the absorption of the other nutrients in the leafy greens. So now I use an avocado or some walnuts as a standard ingredient in my romaine lettuce salads, usually along with a chopped up orange.
    While my red blood cells are apparently a thing of beauty, according to my doctor, I still make the odd green smoothie. Generally using kale, spinach, blackberries, an orange or a couple kiwis, and small amounts of ground flax seeds, sunflower seeds, and pumpkin seeds.

    Warren | Reply

  4. These articles frustrate me a little.  When they say "Tea" they do not say that they mean teas that have cafeene in them.  I had to ask a Doctor about which types of tea would be bad for the anemic me.  I wasn't sure if it was the caffene in coffee and some tea or if it might be related to drinking hot beverages.  I  have a big selection of teas in my home.

    Wendy Rainbow | Reply

  5. Hi there Wendy. Actually, most any tea contains tannic acid, not just teas with caffeine. However, herbal teas tend to contain less tannins that black teas.

    Raederle Phoenix | Reply

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