Plant versus Animal Iron

Image Credit: Sally Plank

Plant versus Animal Iron

It is commonly thought that those who eat plant-based diets may be more prone to iron deficiency, but it turns out that they’re no more likely to suffer from iron deficiency anemia than anybody else. This may be because not only do those eating meat-free diets tend to get more fiber, magnesium, and vitamins like A, C, and E, but they also get more iron.

The iron found predominantly in plants is non-heme iron, which isn’t absorbed as well as the heme iron found in blood and muscle, but this may be a good thing. As seen in my video, The Safety of Heme vs. Non-Heme Iron, avoidance of heme iron may be one of the key elements of plant-based protection against metabolic syndrome, and may also be beneficial in lowering the risk from other chronic diseases such as heart disease.

The data linking coronary heart disease and the intake of iron, in general, has been mixed. This inconsistency of evidence may be because of where the iron comes from. The majority of total dietary iron is non-heme iron, coming mostly from plants. So, total iron intake is associated with lower heart disease risk, but iron intake from meat is associated with significantly higher risk for heart disease. This is thought to be because iron can act as a pro-oxidant, contributing to the development of atherosclerosis by oxidizing cholesterol with free radicals. The risk has been quantified as a 27% increase in coronary heart disease risk for every 1 milligram of heme iron consumed daily.

The same has been found for stroke risk. The studies on iron intake and stroke have had conflicting results, but that may be because they had never separated out heme iron from non-heme iron… until now. Researchers found that the intake of meat (heme) iron, but not plant (non-heme) iron, was associated with an increased risk of stroke.

The researchers also found that higher intake of heme iron—but not total or plant (non-heme) iron—was significantly associated with greater risk for type 2 diabetes. There may be a 16% increase in risk for type 2 diabetes for every 1 milligram of heme iron consumed daily.

The same has also been found for cancer, with up to 12% increased risk for every milligram of daily heme iron exposure. In fact, we can actually tell how much meat someone is eating by looking at their tumors. To characterize the mechanisms underlying meat-related lung cancer development, researchers asked lung cancer patients how much meat they ate and examined the gene expression patterns in their tumors. They identified a signature pattern of heme-related gene expression. Although they looked specifically at lung cancer, they expect these meat-related gene expression changes may occur in other cancers as well.

We do need to get enough iron, but only about 3% of premenopausal white women have iron deficiency anemia these days. However, the rates are worse in African and Mexican Americans. Taking into account our leading killers—heart disease, cancer, and diabetes—the healthiest source of iron appears to be non-heme iron, found naturally in abundance in whole grains, beans, split peas, chickpeas, lentils, dark green leafy vegetables, dried fruits, nuts, and seeds.

But how much money can be made on beans, though? The processed food industry came up with a blood-based crisp bread, made out of rye flour and blood from cattle and pigs, which is one of the most concentrated sources of heme iron, about two-thirds more than blood from chickens. If blood-based crackers don’t sound particularly appetizing, you can always snack on cow blood cookies. And, there are always blood-filled biscuits, whose filling has been described as “a dark-colored, chocolate flavored paste with a very pleasant taste.” (It’s dark-colored because spray-dried pig blood can have a darkening effect on the food product’s color.) The worry is not the color or taste, it’s the heme iron, which, because of its potential cancer risk, is not considered safe to add to foods intended for the general population.

Previously, I’ve touched on the double-edged iron sword in Risk Associated With Iron Supplements and Phytates for the Prevention of Cancer. It may also help answer Why Was Heart Disease Rare in the Mediterranean?

Those eating plant-based diets get more of most nutrients since whole plant foods are so nutrient dense. See Nutrient-Dense Approach to Weight Management.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Discuss

Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.


55 responses to “Plant versus Animal Iron

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  1. “The processed food industry came up with a blood-based crisp bread, made out of rye flour and blood from cattle and pigs”. Ugh…… sounds delish… I wonder if the propeller head marketing guy got a bonus for this..
    Curious, if looking at crackers if a large number for iron is present, would that indicate a blood soaked meal??
    mitch




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    1. Pig blood “sausages” made with pig blood, raisings sugar and flour is a typical sardinian (Italy longevity-famous) sweet. Different versions of the recipe exhist in other parts of Italy. Needlees to say I do not eat that stuf since I’ve always fount it disgusting.




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  2. I had a blood test and my result was 34 ug/L, is that too low? I eat lots and lots of greens, lentil soups and beans dishes.




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    1. Hi Nicole. That’s a lot of iron but it must be digested.

      Caffeine will deplete a significant portion of minerals…up to 30% less digestion.




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      1. That is such a great point K about caffeine stripping vitamins & minerals, I did hear that from my therapist but didn’t realise it was 30% depletion. That might contribute somewhat to my Iron levels increasing from 13 to 20 in the last 2 months, as well as going plantbased I’ve cut out all coffee, tea & chocolate.




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      1. Conflict of interest statement:

        The author is the executive director of the Soy Nutrition Institute, an organization funded by the United Soybean Board and its soy industry members.

        Ugh, how annoying.




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          1. @joe I was replying to darchiterd’s link to a great article about soy, in that the author of that link is the executive director of the Soy Nutrition Institute. I was not talking about Dr Greger which you and others seem to have assumed.

            It’s this stupid commenting system that is terrible in showing comments; it lacks indenting and proper quotation.




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            1. Scott – if you go to the link that Darchiterd supplied to the article on soy:
              https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5188409/
              you will see that the research article was written/publish by Mark Messina in 2016. It states that Mark Messina is the executive director of the Soy Nutrition Institute. If you go to the SNI website you will see that Mark Messina is listed under Staff just as Tjorven stated (above). If you click on the drop-down + under his name you will see his position as Executive Director with SNI and his bio. Here is further information on Dr. Messina provided by Physician’s Committee for Responsible Medicine (PCRM) which is Dr. Neal Barnard’s group. Take a look:
              http://www.pcrm.org/health/cancer-resources/seminars/mark-messina-phd-ms

              While the research article was written by someone from SNI, it did make clear points throughout the article as to what soy was effective as well as ineffective for physiologically. It struck me as fairly honest and well balanced – I read the entire piece which was quite long.

              While Greger has cautioned us all to be wary of research that is “self-dealing”, there are legitimate researchers out there and we should also be wary of discarding that information as well. To me, it speaks volumes for Dr. Messina that he is featured on the PCRM website. PCRM, like NutritionFacts.org is a group I trust to give me a straight deal.
              Hope this is helpful




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              1. Thanks Rachel. I wasn’t discrediting the review; it does look very good info. It’s just that I saw that conflict of interest and know you’d get soy haters / carnists picking up on it.

                I look forward to reading it all :-)




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  3. My wife has hemochromatosis. We have whole food plant based for nearly seven years. Our understanding is that high iron produces more oxydation as you noted. But when all her iron is non-heme is there still the danger of diseases from oxydation? Her doctor asserts this view.
    Good news, we believe her diet has effectively attenuated the impact of the disease.




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  4. And then there is the risk of all kinds of trouble with the brain, see
    -Smith MA, Harris PLR, Sayre LM, Perry G. Iron accumulation in Alzheimer’s disease is a source of redox-generated free radicals. Proc Nat Acad Sciences of the United States of America. 1997;94:9866–68.
    and
    -Stankiewicz JM, Brass SD. Role of iron in neurotoxicity: A cause for concern in the elderly? Curr Opin Clin Nutr Metab Care. 2009;12:22–29.




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  5. Impossible Foods is using plant based heme iron in their burger patties. Would plant based heme iron have similar risks to animal derived heme iron?




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    1. Thanks for your question.

      That’s a great question and I have asked myself that before when I watched their video. I suspect it will have the same harmful effects as animal based iron, unless some other component in plant (e.g. high antioxidant properties of herbs/spices) used in the burger will cancel out there harmful effect of heme iron.

      This is only an opinion, hope this answer helps.




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    2. Mike, Thank you for asking this question. I was wondering the same thing myself.

      I was intrigued when I heard about Impossible Foods’ plant based burgers, but I found the idea of the “plant blood” off putting. When I heard that they were able to recreate the flavor of meat by synthesizing heme iron from plants, I immediately thought of Dr. Greger’s video which recounts the inability for our bodies to regulate heme iron absorption. ( The Safety of Heme vs. Non-Heme Iron: https://nutritionfacts.org/video/the-safety-of-heme-vs-non-heme-iron/)

      I suspect that this product is as just harmful as meat from that perspective. A three ounce Impossible Foods burger patty has 11 grams of saturated fat so it’s not exactly a health food. (Source CR: http://www.consumerreports.org/veggie-burgers/meatless-impossible-burger-debuts/ )

      I suppose that we won’t know for sure until, “it is put to the test,” but who would benefit from such a safety study. Certainly not Impossible Foods or their investors…




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  6. Iron in dried fruit: I read years ago (but cannot find a resource now) that the iron in dried fruit such as raisins largely comes from the iron surface on which they are dried, similar to cooking with an iron skillet. On http://www.nutritiondata.com, their data shows dried apricots at .3mg of iron per ounce, dehydrated apricots at 1.8 mg per ounce, and for fresh apricots, subtracting out 100% of the water, .8 mg per ounce. It’s hard to make sense of all this.

    So, for my home dehydrated fruit made on plastic trays, who knows? Not that it matters. A diet that includes a variety from all the plant-based food groups is the way to go. Best not to over-think it.




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  7. When I first heard of the danger of too much iron I was concerned the implication for heart related issues. I did not hear about the difference between heme and non-heme iron. It was suggested that giving blood would be beneficial by lowering iron count and generating new blood. I religiously gave a pint of blood every three months. Ironically I would periodically have an issue because my iron count was too low for them to take my blood. I had a basically vegan diet with only rarely eating eggs or yogurt/kefir and lots of greens. Eventually the phlebotomist identified my problem. The tannins in black tea reduces iron count, I was drinking two cups of black tea a day. controlling my tea drinking (green/chamomile/hibiscus-black cherry) has resolved the iron issue. My experience, be a dark green vegan lots of beans control the black tea and you will have no iron issues




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    1. Thanks for your comment Harvey.

      I would suggest adding a vitamin C rich product with your meals as “Ascorbic acid will overcome the negative effect on iron absorption of all inhibitors, which include phytate (6), polyphenols (32), and the calcium and proteins in milk products (33), and will increase the absorption of both native and fortification iron. In fruit and vegetables the enhancing effect of ascorbic acid is often cancelled out by the inhibiting effect of polyphenols (34, 35). Ascorbic acid is the only main absorption enhancer in vegetarian diets, and iron absorption from vegetarian and vegan meals can be best optimized by the inclusion of ascorbic acid–containing vegetables” (see here).

      Hope this answer helps.




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  8. Type 2 diabetic here. My sugars were high but didn’t think they were too high. I run and last year I had to stop because of exhaustion after a few miles. I was eating lots actually too much but still not able to run. Eventually found out my ferritin was about 11 a bit too low. Tried iron supplements with Dr supervision. Still didn’t get the feritin up. Hemotoligist said get your sugars untercontrol. Seems like excess sugar interferes with non heme iron absorbing properly. Dropped my A1c to under 7 and I am going to run a 1/2 marathon on the weekend.
    So diabetics get your sugars down to absorb iron . Worked for me




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    1. Have always wondered why A1c of 7 considered ok for diabetics, but for others standard is A1c no higher than 5.7. Hope someone can explain this!




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  9. Perfect timing!! A friend and I were just talking about how our nails are beginning to split and curve upwards somewhat. We are both post-menopause and have been eating plant-based for over eight years now. Hmmm…low iron? Dr. Greger mentions, “about 3% of premenopausal white women have iron deficiency anemia these days,” but what about postmenopausal white women?

    Aside from getting tested to confirm an iron deficiency, is the premise that one just eats more iron-rich plants (lentils, chickpeas and such) and avoids the iron supplements? I’m gluten-intolerant and have a hard time digesting rice, by the way, so increasing grains is a bit tricky, as I can only manage some buckwheat, quinoa, and gluten-free oats. And blood crackers – oh, disgusting.




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    1. How about adding blackstrap molasses to coffee or raw cocoa? Also cracked chlorella is fairly high in iron. Eat something with a lot of vitamin C with it.




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      1. I do iodine drops daily from my integrative physician that he gets formulated for us. I don’t want to overdo the iodine, since I have hypothyroidism. I live in Michigan and we’re known as “the goiter belt,”
        since so years ago, the glaciers melting wiped out the iodine in our soil.
        I need more time walking the beaches of California barefoot, haha! I also eat a fair amount of spirulina, nori, and seaweeds, but I’ll try adding some kelp to my soups and stuff. Thank you :) I did stop eating iodized salt years ago, but when I eat out, I do use it 2-3x/week. Thanks for the idea and food for thought :) Much appreciated.




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      2. Great suggestion – thank you! We have been using sea salt for several years now, and I do use a kelp shaker, but perhaps not enough. Sounds like it’s time to run some blood work to check iodine and iron levels, and see if these might be the culprits. I also ordered some good quality spirulina to add to the morning smoothies, too.




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  10. There are an estimated 2 billion iron deficient people worldwide. The “processed food industry” did not come up with these for first world problems, and the links are all to government funded studies assessing these means as opposed to pharmacological iron tablets, that are often also poorly tolerated and have a range of intolerable gastrointestinal effects. Not to mention, combining protein sources along with other nutrients is well-documented to increase iron absorption. I don’t know why these specific studies are being demonized in this paragraph to point out the unhealthy issues of processed foods, of which there are many.




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  11. Iron is also highly implicated in Alzheimer’s disease. According to a book I read (I’ll look for the title), it’s even more influential than aluminum or excess protein.




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  12. Since I was pregnant with my first child 12 years ago I’ve always had very low Iron. Ferritin was always around 13 ug/L.
    I was told eat more meat, take these iron supplements! Nothing worked Ferritin level stayed the same, but Cholesterol went through the roof with all the meat. I decided to go plant based 2 months ago & loving it, no meat no dairy & guess what? Ferritin is up to 20 ug/L after only 2 months which is still a bit low but it’s at least in the normal range. Total cholesterol & bad cholesterol is also down significantly & Ive lost 6 kgs, so will be continuing very happily with my new plant based lifestyle.




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    1. hi Naomi, I had the same experience! I’ve been chasing calcium and iron most of my omnivorous adult life with no luck in getting either one to adequate levels.. until now ! WFPB eating for almost 2 yrs and my calcium is perfect according to the doc, and iron is 25 (it was 12 to 15 in years prior). No supplements, just whole foods and lots of leafy greens.




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      1. Hi Susan,
        I don’t meant to pirate your reply above in this thread, but thanks for mentioning your iron level number! I was 12 actually for a long time, but once I made switch to whole foods plant-based diet, my levels went up to 42 from taking iron supplements. I stopped my iron supplements since every type and brand upset my tummy. My recent level was 22. They are calling it “low” but not anemia. I am thinking it’s okay to be in the 20s level with iron. I mean, it’s in the low range, but it’s still “normal,” not that I aspire to be normal ever LOL, ha!




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        1. hi Lisa! Thanks for your comments. My doctor also said my levels were still a bit low, BUT she is amazed that they are so good while I am eating plants. I think we’re doing fine imo Lisa.. Dr Greger says in this video that ferrotoxic disease occurs in levels above 50ng/mL. https://nutritionfacts.org/video/donating-blood-to-prevent-cancer/ Just as an aside, I never did this well on blood tests (of all kinds) eating meat eggs and dairy and quaffing supplements. Simple fresh food seems to take care of almost everything. (B12) All the best to you Lisa!




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          1. Susan, aww, thanks! I agree re: us doing well. I also totally agree regarding plants taking care of stuff. My iron is actually way better than when I used to be pescatarian, haha! :) Thanks for sharing the video too of Dr. Greger, much appreciated and the best to you as well. xo




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  13. It took me quite a while to realize that my health deteriorated every time I took iron supplements. Now I avoid all heme iron (I’m a vegan) but I have found a few unexpected sources of iron:
    Frying acidic food in cast iron pans or woks
    Black olives
    Iron-fortified cereals
    Chlorella and spirulina also contain a lot of iron, but presumably that is non-heme




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  14. hi I am 33 years old, Scandinavian, white, slim, normal weight, so seam like those 3% that is affected by low iron. have a long term history of eczema and allergy (dust, pollen) that is under control due to supplement that help with food sensitivity that usually leads to outbreak. However such may have contributed and affected my immune system due to inflammation long term. In the last couple of months I have lost a lot of hair and also have dry corners of the mouth (skin next to corner of mouth). I went to the doctor that found some elevated sugar levels and low iron storage. he recommended eating liver pate to increase iron storage and to eat iron rich food with c-vitamin, avoiding coffee and tea 1h before food, and 2 h after food. what recommendations do you have. Do you think that the sugar levels it what affecting the uptake of iron? how should I keep sugar level down, and increase iron absorption. I eat generally a very healthy vegetarian diet without much dairy but have avoided red meat for a while but may need to start eating such again. I am thinking of starting high intensity training to lower sugar levels and also take a supplement of iron and also add liver pate to the diet to make my hair start growing again.




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  15. To dr. Greger

    Please make a post about how much fat is too much?!
    As a follower of the daily dozen and of your website you never relate to the question is it possible to overdo the good fat like eating too much nuts and seeds in one day is there no limitation to it?

    Thank you




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  16. Oh wow! Thank you for this post! It’s very timely for me. I’ve been struggling with low iron the past 3 years. I’m 45. I’ve been plant-based most of my life! I’ve never had an issue until my early 40s. I think some of my low iron could be due to heavy periods. Which I think is from low thyroid (I’m being rechecked since UGH, I had no idea for 20+ years that you’re not supposed to take your meds before your bloodwork like mine, Nature-Throid due to the T3 aspect. Ugh!)

    But, I’m in iron hell. I do have decent energy, but…Omg, the hair thinning/loss and brittle nails I’ve experienced the past 3 years are driving me insane!

    My recent iron blood work showed a level of 22, which my integrative physician considers “low.” I’m very conflicted about taking iron supplements. They are horribly constipating for me, even a plant-based, liquid supplement I recently found is constipating!

    I eat all the plant-based, iron-rich foods mentioned in this post, along with Vitamin C and other vitamins like B12, too many to list here. I’ve been at my wits end. The past 4 months too, blood work reveals I have a low alkaline phosphatase, which they’re trying to say is possible deficiency. I’m getting blood work to assess intracellular nutrients and waiting for the results. That should be interesting, ha! Add in my recent high sedimentation rate in the mix and I wonder what the heck is going on with me. I feel GREAT, have energy…except my iron supplements wreck me :(

    I’ve tried everything to try to get my numbers to the levels that are considered “optimal.” I did for a while take a prescription, high dose iron about 1.5 years or so ago, but it wrecked havoc on my gastrointestinal tract.

    This stuff sucks for women, just wanted to be honest and transparent. There’s some kind of connection I wonder between low thyroid, low vitamin D, low B12, low iron levels in the blood. I’m so willing to change anything that isn’t working in my vegan diet and/or take additional supplements. I’d even get a second or third opinion on this (which is quite a bit for me since blood work sucks for me, since my veins don’t like it).

    Sorry to be longwinded. Been researching and researching. Maybe that’s why I’m exhausted at times? I’m half tempted to just tell my doctor, “Hey, my numbers with iron might be low, but they’re still considered normal.” :)

    Thanks…




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    1. Do you take any iodine or zinc? Iodine is an essential nutrient necessary for thyroid function and if you are not eating a bit of seaweed regularly, perhaps you are not getting enough. Zinc also tends to be low on a plant-based diet.




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      1. Hey, thanks for those! That’s very helpful! I’ve been taking a zinc supplement for a month or two, but maybe I need a higher dose? I also eat spirulina powder daily and vegan nori rolls at least once per week and snack on a seaweed now and then. :)




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  17. Iron levels and pneumonia

    What if I told you there’s an easy way to avoid pneumonia as you get older? If you’re over the age of 60, you’re probably very interested. That’s because the older we get, the more likely we are to come down with pneumonia. And pneumonia can be deadly. So avoiding the illness should be a high priority.

    So how can you avoid pneumonia? A group of researchers out of the University of Virginia School of Medicine found that a certain hormone can help prevent the illness. Here’s how it works. As you may know, pneumonia needs iron in your blood to survive and grow. The more iron you have in your bloodstream, the easier it is for pneumonia to take hold.

    But the hormone hepcidin limits the spread of pneumonia bacteria. It does this by hiding the iron in your blood so the bacteria can’t find it. Your body produces hepcidin in the liver. That explains why people with liver disease are more susceptible to pneumonia.

    The researchers genetically modified mice to lack hepcidin. They found these mice were particularly susceptible to bacterial pneumonia. Nearly all of the mice with this modification had the pneumonia bacteria spread from the lungs into their bloodstream, ultimately killing them. This is how pneumonia spreads in people as well. Without the hormone, the mice weren’t able to hide iron away from the bacteria, allowing the pneumonia to spread.

    So how can you make sure you’re producing enough hepcidin? The researchers pointed to a drug that’s already in development that mimics the function of hepcidin. While this might be an answer for people who have hereditary hemochromatosis (chronic iron overload), there might be an easier way to avoid pneumonia.

    First, make sure you’re donating blood regularly if you can. The Red Cross has a special donation they call Power Red. According to the Red Cross, “Power Red is similar to a whole blood donation, except a special machine is used to allow you to safely donate two units of red blood cells during one donation while returning your plasma and platelets to you.” Since about 70% percent of your body’s iron is in your red blood cells, this donation can help reduce your iron load. Not only will you be reducing your risk of pneumonia spreading, you’ll help save lives at the same time. Steve Kroening, ND




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  18. This is very interesting, Fred. There is also another paper that talks about the fact that it’s the freely available iron that is a great growth promoter for bacteria. When there is a drop in pH or Eh more iron becomes available for bacterial growth. Bullen et al. 2005: Iron and infection: the heart of the matter.

    I had pneumonia a few years back, prior to that I had been injected with iron three times. Now I refuse any more injections or iron supplements, and my doctor is really concerned about my low ferritin of 16. I would rather have a ferritin on the low side than pneumonia!




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  19. Ok, so how can I tell if iron is non heme or not. I am taking Ferrous Sulfate. I think more comes ‘out’ than stays in. Stools are disgustingly deep dark green, looks almost black. I have been raking Vit C to help absorb the iron.




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    1. Ferrous sulfate is not a heme iron, heme iron is bound to hemoglobin, myoglobin and possibly other compounds found in animal flesh and blood.

      In 2012 Dr Greger put out a video called ‘Risk associated with iron supplements’, there he points out that iron supplements seem to increase oxidative stress, but he does not go into the question of whether supplemental iron uptake is regulated in a heme or non-heme manner.

      So I don’t know why I get really sick on iron supplements, maybe I end up with free iron floating around and causing oxidative stress or infection???




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    1. Hey Barbara, thanks for writing! But I’m not sure whether you actually mean that your INTAKE is limited or your ABSORPTION is limited. Obviously, your INTAKE depends on how many iron-containing foods you eat! Absorption is another story, which depends on your current iron status, the amount of vitamin C in your diet, whether or not you take acid-suppressing drugs, if your diet is very high in fiber, and other factors. Iron absorption IS limited by the gut’s transport mechanisms to some degree, but I don’t know if 1 mg per day is the correct amount.




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