Cereal fillers

When I read words like “enriched” and “added iron/calcium/etc” on a packet, I can’t help but wonder where the added nutrients come from. How are they produced, and are they the best things for my body?

A recent e-newsletter from Raw Pleasure featured this YouTube clip about how to establish the fact that there are little bits of metallic iron in your favourite breakfast cereal:

My first reaction: Thank goodness I don’t eat packaged cereal!
My second reaction: What does this actually mean?
[yes, I am becoming a healthy skeptic in my old age :)]

While I could believe that cereal manufacturers would add iron filings to cereals, and that FSANZ would let them, I couldn’t believe that no major action had taken place or been publicised about the issue. This particular YouTube video is dated May 2009, with other similar videos being created as early as 2007. I move in healthful circles; why had I not heard about this before? Surely it meant this was not such a big deal. All the same, something just didn’t sit right with me…

Most of us know that iron is an important mineral for our body, and some of us are acutely aware of this because of personal experience with anaemia. I first suffered from iron-deficient anaemia when I was 16: I was so tired that I couldn’t drag myself out of bed. Iron is essential for regulating cell growth, cell differentiation, transporting oxygen around the body and immunity.

Although I know metallic iron is related to the iron you find in wholefoods, like cacao, seaweed and spinach, the burning question in my mind was: “can this form of iron be readily absorbed into our bodies?” In other words, is it as bioavailable?

So what are these filings? Consumer knowledge of iron filings in cereal dates back to at least 1984, starting with an experiment by Dr Babu George.

Where iron filings are used in food, these are known as “food grade iron filings”. What does this mean? Basically, they are powdered iron filings. These powdered iron filings are also known as “reduced iron”. This is iron in its metallic, or elemental, state and that doesn’t sound too appetising to me.

Are iron filings used in Australian cereals? The first thing that I wanted to establish was whether or not reduced iron is used to fortify Australian cereals. Given that the cross-section of YouTube clips I viewed appeared to be from Europe and the US, I kind of hoped this was only happening elsewhere.

I investigated labels from three popular Australian cereal manufacturers to find out as to whether or not they list the form of iron they use. I won’t name them here, but I will say that only one of the manufacturers included details on their website regarding the form of iron fortification used — and it was indeed reduced iron.

Now I knew that this issue was relevant to Australians.

How readily are these iron filings absorbed into the body? On the face of it, the first real research article I found, Iron Absorption From Elemental Iron-Fortified Corn Flakes In Humans. Role of Vitamins A and C, appeared to be exactly what I was after. It clearly detailed research into the relative absorption of different forms of iron, found that the absorption of reduced iron could be encouraged to an acceptable rate, and reached the conclusion that supplementation with this relatively inexpensive substitute is the most cost effective way to supply populations with the iron they need.

Wait a minute. Did this study recommend a low-grade, poorly absorbed form of iron fortification in cereals? Because it’s cheap? Seriously, why bother?

A closer look at the first page revealed it was a study sponsored by none other than a cereal manufacturer with a direct interest. This piqued my curiosity.

Dr Tim O’Shea put together this useful reference regarding minerals and how available they are to our bodies. Note that metallic iron is not highly bioavailable.

So is there another place the iron could be broken down? Digestion starts in your mouth and it continues past your stomach to your small intestine, with the aid of your pancreas, liver and gall bladder. Iron absorption happens in the duodenum, the first section of your small intestine, and this converts iron from its ferric (Fe3+) to its ferrous (Fe2+) form.

So where does the body convert metallic iron to its ionic form? All I could find were explanations on how plants make that conversion for us but, given the fact that numerous studies do show limited absorption from metallic iron, I assume that our stomach acids are strong enough to work on the surface of the iron filings to create a small number of iron ions.

Still feeling that iron filings might not be the greatest thing to eat, I looked further.

What stops iron filings from rusting in our food? When iron is exposed to oxygen, it rusts. To keep metallic iron from rusting in domestic & industrial applications, it is either coated (eg. with zinc, grease) or mixed with another element (eg. carbon). Food grade filings are powdered, which would leave more of their surface available to oxidisation. I couldn’t find anything online that mentions how food grade filings are protected from rust, or who produces reduced iron for food — but I assume that something must be added to them, or I would expect the distinctive taste to come through in our food.

I did have the thought that perhaps there just isn’t enough iron added to our foods for a significant flavour change following rusting, however a number of studies online mention the fact that the more absorbable ferrous sulphate is often avoided as an additive because of its taste — so that makes me think that there is sufficient metallic iron added to warrant a taste change on rusting.

If manufacturers follow the WHO recommendation to use twice the amount of reduced iron as they would ferrous sulphate if they choose the former as a fortificant, I would think that rust and, hence rusty flavour, would be even more pronounced. [And, yes, I was surprised to note that the WHO supports the use of metallic iron as a supplement in any form.]

So, aside from not being readily absorbed into our bodies, are iron filings actually bad for us to eat? Dr Thomas Levy discusses the issue of enriched food in the May 2002 issue of “Health e-Bytes”, telling us that iron filings are toxic to our bodies. While Dr Levy talks in general about the ills of fortified foods, including the fact that they are so processed that they are stripped of their base nutritional value before fortification, he doesn’t mention how or why iron filings are so toxic/dangerous to our health.

This 2010 article from Dr Joseph Mercola also warns us to avoid fortified foods altogether. Like Dr Levy, he stops short of explaining the specifics of why reduced iron is such a baddie, but he makes an excellent point: would any of us actually choose to feed our child a pinch of iron filings every morning? I know I wouldn’t.

Articles and studies regarding iron toxicity (like this one from The Eck Institute of Applied Nutrition and Bioenergetics and this one from Cornell University) mention potential causes of toxicity as being cast iron cookware, occupation, and over-consumption. My limited understanding of iron metabolism leads me to believe that iron toxicity does not necessarily result from the amount our bodies absorb in the duodenum: the harmful effects of iron toxicity could also relate to the ways in which metallic iron is stored and eliminated from the body.

To conclude, when elements are extracted from nature in non-bioavailable forms and reinjected into food, it is akin to molecular gastronomy: reducing food down to its most infinitesimal level. And when food is reduced to this level, it is not balanced.

I am also concerned about the possibility of added “filler”/mixer to prevent rusting in reduced iron. If a compound ingredient (eg. tomato sauce) makes up less than 5% of the total weight of a food product in Australia, it is lawful for a manufacturer not to include information about it. This is, of course, unless there is a known major allergen included. The problem with this is that many additives, including fillers, that produce reactions are not formally recognised as allergens (for an example, read Jennifer’s story about additives 627, 631 & 635).

The form of added minerals and their fillers is not necessarily obvious. The most effective defence against eating unwanted additives is to avoid processed foods altogether.

Nature incorporates so many excellent nutrients in our foods and in beautiful balance. Many of the cofactors for nutrient absorption are already in the wholefoods we eat, so long as the environments in which our foods thrive are not nutrient-deficient to start with. For this reason, I would include a variety of whole, organic and free range foods from a variety of sources in your diet.

If you are worried about whether or not your iron intake is sufficient, a good place to start looking is your own lifestyle. Is the problem to do with having sufficient iron in your diet, or is it about the level of absorption by your body? Iron absorption is hindered by caffeine intake and low levels of vitamin C, iron competes with other minerals for absorption (meaning: your intake of other minerals also needs to be balanced), and a low sleep/high stress lifestyle leads to poor absorption of all nutrients.

What I have presented here is my interpretation of a rudimentary internet forage — and possibly a little too much insight into how my brain works. I am really keen to learn more. If you have thoughts or feelings on this topic, or can shed more light, please leave a comment.

Yours in mindful eating,

H ๐Ÿ™‚


24 July 2012: I removed the paragraph linking to a set of University of Oregon lecture notes after the comment from Pete Richter [below] because it didn’t make a point either way. The equations did not approximate the full action of digestion in the stomach, or the interaction of food enzymes/cofactors in digestion, and HCl does not wholly represent gastric juices, which vary in strength and composition from person to person.

20 June 2018: after discovering broken links, I removed my 4 November 2011 addendum about the supplement Adya Clarity. I still have not met a single person who has used it.

Some further reading on bioavailability of iron and factors that enhance/inhibit its absorption:

J D Cook, S A Dassenko, P Whittaker; Calcium supplementation: effect on iron absorption, The American Journal of Clinical Nutrition, Volume 53, Issue 1, 1 January 1991, Pages 106โ€“111, https://doi.org/10.1093/ajcn/53.1.106

Richard F. Hurrell; Preventing Iron Deficiency through Food Fortification, Nutrition Reviews, Volume 55, Issue 6, 1 June 1997, Pages 210โ€“222, https://doi.org/10.1111/j.1753-4887.1997.tb01608.x
[PDF accessible from: http://doc.rero.ch/record/290231/files/nutritionreviews55-0210.pdf]

Birgit Teucher, Manuel Olivares, Hรฉctor Cori; Enhancers of Iron Absorption: Ascorbic Acid and other Organic Acids, International Journal for Vitamin and Nutrition Research, 74, 2004, Pages 403-419, https://doi.org/10.1024/0300-9831.74.6.403.
[PDF accessible from: https://www.researchgate.net/profile/Manuel_Olivares/publication/7991048_Enhancers_of_Iron_Absorption_Ascorbic_Acid_and_other_Organic_Acids/links/565660d808ae1ef9297a01e7.pdf]

>See also: Science Direct’s research summary on iron overload



  1. Very interesting and well researched article Hannah! It’s just amazing how I could never have heard of this. Those “in the know” love to keep the “common man” ignorant. This is just another reason to eat raw and organic, as if there weren’t already enough reasons.

    I’m still planning my guest post. I actually made the recipe I planned to post with the blog entry so I could take a photo then stupidly ate it before I took the photo! Ha ha! Hopefully it’ll be worth the wait… xo


    • Thanks, Josh. I am constantly surprised – in a bad way – about what goes into processed foods.

      It’s always a good sign if your food is too edible to photograph. I am really looking forward to that guest post!

      H ๐Ÿ™‚


  2. Dear Hannah,
    Last Thursday (11 August 2011) ABC TV Catalyst science show did the iron filings experiment on Australian breakfast cereal.
    You can view the video on the Catalyst website.
    This link might take you to it
    I haven’t ever eaten commercial breakfast cereals and get all my iron from non animal sources and plenty of vitamin C from citrus fruits. My iron levels are tested once a year and they are fine.

    (South Australia)


  3. Thankyou for this wonderful write-up. I first saw the videos a few months ago, and was sure Australia couldn’t be as callous as overseas. Well I was wrong!
    Makes me very glad I don’t eat packaged breakfast foods, and very concerned for those that prefer convenience foods for their most important meal of the day.


  4. Hi Hannah,
    I worked for a large cereal manufacturing company (in Australia) for nearly 10 years and have seen the iron being added first hand. I didn’t think much of it at the time (other than it being a bit odd to add iron filings to food at the beginning of the process when at the other end of the production line metal detectors were installed to remove “contaminated” product) – I have since been educated to take a greater interest in my food and no longer eat any refined/packaged foods.


  5. >Tom – I appreciate the trackback ๐Ÿ™‚

    >Pamela – thanks for the link, which shows an even clearer experiment than the others I have seen. Interesting that, while she mentions that reduced iron is “tested for safety” [how & by whom?], Dr Demasi also mentions that its actual level of absorption is unknown.

    >Ally – thanks for your comment. I am heartened when I see more people asking questions about how their food is sourced & produced.

    >Phil – I appreciate your feedback. I told some of my work colleagues about my recent research and they didn’t believe me! Sometimes truth is stranger than fiction.

    H ๐Ÿ™‚


  6. It seems “elemental iron” does not oxidise that quickly making it suitable for use in some foods with shortish shelf lives & does not require additional anti-oxidisers.

    Another issue is most of it comes from China …… so who knows what other contaminates it has in it (all iron used has some trace elements of other metals in them, wherever they are from) or if it’s really food grade, given their bad record.



    • Thanks so much for your comment, Ben! I reached the same conclusion re elemental iron.

      Something that has concerned me about additives is the risk of contamination, particularly where heavy metals are used in their creation and where we can not be assured of quality (eg. due to a country/organisation’s lack of obvious controls/assurance or previous transgressions).

      H ๐Ÿ™‚


  7. Quick correction: You wrote

    “This set of 2010 lecture notes from the Chemistry Department at the University of Oregon shows that iron is not bioavailable when exposed to stomach acid… I would have thought that the iron must first be able to be broken down by the digestive process in order for these vitamins to function โ€“ and it certainly was not broken down by the stomachโ€™s digestive juices.”

    However, if you actually read the procedure it quite explicitly states that the dissolution in HCl is meant to simulate the breakdown of the filings in the stomach! This is where the ionic form becomes available to the body, and answers the question you posed in the following paragraph.

    As for the rusting issue, the “rust taste” is generally more of a problem for the higher bioavailability iron sources (see article at http://jn.nutrition.org/content/136/4/1059.full). I do not claim to be an expert on why, but I would guess that this happens for ferrous sulfate and related species because they are readily homogenized into the food (since they are water-soluble) and thus when they do oxidize, they are dispersed evenly throughout the food and easily tasted; I’m guessing that the metallic iron also oxidizes somewhat, but more slowly, and since they are hard little bits, they are harder to taste because the rust doesn’t permeate the food in the microscopic sense. If you’ve ever dripped a bit of ferrous sulfate solution into a jug of hard water, swirled and waited a couple minutes, you’ll see what I mean; over time the liquid becomes brown from rust and tastes like it too!

    Why do we still use iron filings? From the article I read, it seems it’s a problem of aftertaste (filings don’t give a bad taste, whereas ionic iron does) and rancidity-prevention. Filings seem to be reasonably bioavailable, and I’m guessing the improved availability of “pre-digested” ionic iron is outweighed by the crappy taste and shorter shelf-life it imparts.

    Overall, I think adding the filings are a good thing, despite what the eco-freaks may say; mineral deficiency and in particular iron anemia used to be a big societal health problem back in the “bad old days” before food enrichment, and nowadays only a few people in industrialized countries develop these maladies. As a chemist, I am sometimes offended by the attitudes of people like poster Joshua Jones, who seem to think we’d be better off living like people in the 1700s, and who are unaware that millions of people would have unnecessarily died of malnutrition if it weren’t for simple little ideas like adding iron filings to food. That’s not to say that bad mishaps happen (like melamine added to cat food and baby milk); it’s good to question what goes into our food, but overall it’s safe to say food enrichment probably does more good than bad.


    • Thank you for your well-considered comments, Peter. I love it when readers actually follow my references and hold me to account – especially when they are as qualified as you!

      I appreciate you pointing out the fact that iron converted to Fe2+ by the reaction with the stomach’s acid is bioavailable, although the experiment also points out that iron absorption occurs in the small intestine which is more basic – and, in this environment, some of the Fe2+ converts into unavailable Fe3+ (in the form of iron(III)oxide), thereby reducing the bioavailability of the iron. I will, however, include an addendum to this post, further to your comments.

      There are so many factors that impact on the absorption of reduced iron, including substances consumed with the iron and the surface area of the filings. The acidity of gastric juices also varies from person to person, which affects absorption levels.

      I am an educated person who simply wants to know exactly what is in my food, without any cloaked references or meanings, so that I can make informed choices about what goes into my body. Because I feel great on a diet including very few processed foods and mostly organic whole foods, and I listen closely to what my body is telling me, I am fairly certain that my body is getting what it needs without the need for consuming mystery ingredients.

      I do not believe that we would necessarily be better off living like people in the 1700s, and I didn’t get that sense from Joshua’s comment. I do believe that those of us in developed nations live in a privileged time where we can access many different whole foods from varied sources. This leads to a greater likelihood of adequate nutrition from diet – or from good quality supplements in the case of a verified deficiency (although I would want to understand the underlying cause before fixing the problem with a bandaid of supplementation) – rather than a daily barrage of blanket ‘fixes’ for which there is no established need.

      [Indeed, so much latent supplementation occurs within processed foods in the Western world that I wonder at the fact that we still see these deficiencies in the general population. Does this have something to do with the fact that many people have a diet high in processed foods, and that refined foods consume our vital nutrients in order to be processed by our bodies? I would be interested to find out about the overall health of those people who eat highly processed breakfast cereals and other foods, versus those who choose whole foods.]

      At the end of the day, reduced iron is a cheap form of mass supplementation that does not work as well as other forms, and a high iron intake may actually cause harmful effects for those with an otherwise well-rounded diet [see http://www.yourmedicaldetective.com/drgrisanti/iron.htm and http://www.sciencedaily.com/releases/2003/06/030610081311.htm for example]. We are all different, with different nutritional requirements to keep our delicate systems in balance. I think it’s time we started listening to our own bodies, doing our own research, and taking responsibility for our own choices about what we consume.

      Thanks again, Peter. I look forward to your further thoughts.

      H ๐Ÿ™‚


  8. My son is very allergic to all types of metal. He cannot wear or have any metal touch his skin without having a reaction. I think some of his current skin and stomach problems may be connected to reduced iron in the cereals he is chosing. He eats a lot of as a busy college student. I think he is reacting to the iron in its metalic for inside his body. Could this be a valid assumption? I would appreciate your obviously very knowledgeable opinion.


    • I really empathise with your son, Heidi. While excess iron can result in skin reactions, I recommend further investigation before attributing his symptoms to a specific cause.

      It may be that your son has a gluten intolerance, an issue with certain additives, or that stress affects him as allergic reactions – or it could be a combination of dietary & lifestyle factors. A good place to start is with an open-minded doctor, naturopath or nutritionist, and a process of elimination.

      I wish him (and you) all the best!

      H ๐Ÿ™‚


  9. Forgive me for asking a really dumb question – but what are the alternatives to commercial cereal?

    My kids like porridge just fine in winter but we live in a climate where 75% of the year we have 36C+ days and it’s just too hot at 7am to eat porridge.

    I have tried them with muesli (there was fierce mutiny) and now offer them toast (homemade 5 seed loaf) or commercial cereal for breakfast (usually cheerios as they – surprisingly – have less sugar than most other cereals).

    I have one child with an egg allergy – so a quick scrambled egg on toast isn’t an option.

    What do you have for brekkie instead of commercial cereal?


    • Thanks for your comment, Rebecca! I too faced a mini revolt when I placed my raw granola in front of Mr 4, although I persevered and he had to admit it wasn’t too bad (although he still prefers to eat other things for breakfast!).

      There are many alternatives to commercial cereal, including chia porridge (which isn’t hot in temperature), buckinis (here in Australia there is a company that caramelises activated buckwheat, and they have a version with dried fruits), or a raw “cluster” type cereal. Your local organic store may have some good alternatives to try.

      You could also serve fresh fruit with yoghurt, make your own muesli bars or whip up a protein-rich smoothie.

      Homemade toast is great; I use a wholemeal sourdough some mornings. It’s a shame that one of your children has an egg allergy as organic, free range eggs can make for a quick & wholesome breakfast – but you could also serve toast with homemade baked beans and avocado. There are no set rules.

      Good luck, and please let me know how you go!

      H ๐Ÿ™‚


  10. My grand dad who is living in Vietnam and 95 years old and still doing well, smoking his favorite cigarettes. He doesn’t see doctor and take no pills, he eats anything. My grandmapassed awy at 85 because of motorcycle accident but she was healthy. food in Vietnam are not iron fortified because thanks gog, they don.t spend billions of dollars to study the benefit or bc unnessessary cost added to food. The question is, does it really matter? Life expectancy in Vietnam or western world are almost the same and depends on individual gene I guess.


  11. Great post. I had the same reaction when seeing the video and searched for info on the health impact and found this post. I was not disappointed and will be following your blog.


  12. Let me pick this apart:

    > “Wait a minute. Did this study recommend a low-grade, poorly absorbed form of iron fortification in cereals? Because itโ€™s cheap? Seriously, why bother?”

    Yes. Yes it did. And for good reason. Even though reduced iron is less bioavailable, it’s easy and cost-effective to add more of it to compensate, so the body still absorbs the right amount of iron. If it’s cheap, then it’s available to a larger population – thus lowering the prevalence of anemia among poor people.

    > “What stops iron filings from rusting in our food? When iron is exposed to oxygen, it rusts. To keep metallic iron from rusting in domestic & industrial applications, it is either coated (eg. with zinc, grease) or mixed with another element (eg. carbon). ”

    Iron filings are not coated. There’s nothing to stop them from rusting. They will rust when in contact with water, salts, and acids in your stomach. Rusting is oxidation; it produces Fe 2+ and Fe 3+ ions. Maybe that’s why studies show that the body will absorb some of it.

    > “If manufacturers follow the WHO recommendation to use twice the amount of reduced iron as they would ferrous sulphate if they choose the former as a fortificant, I would think that rust and, hence rusty flavour, would be even more pronounced.”

    Not at all. Sulfur is well-known to produce off-flavours in low concentrations. Iron is not.

    > “would any of us actually choose to feed our child a pinch of iron filings every morning? I know I wouldnโ€™t.”

    That’s because a “pinch” is hard to measure, and could easily be way too much iron. The iron in fortified foods, on the other hand, is carefully measured.

    Remember, there are 7 billion people on Earth, and our farmland is limited. Some nutrient-rich foods are inefficient with land use. We should not keep cutting into our forests to make more farmland.

    Fortification has great potential for providing nutrition at a low cost to the environment.


    • Thanks for your thought, Sanjit – and please accept my apologies for letting your comment slip past me.

      In the almost-five years since I wrote this post, my basic point of view hasn’t shifted: blanket supplementation is what I’m really uncomfortable about here — the assumption that we all need more of a good thing — without establishing a deficiency in the first place.

      Maybe I should have been clearer in my post about the fact that I am talking about cereals on my supermarket shelf, in the developed world. In the meat-rich Western diet, we get plenty of iron: the challenge is to make it available to our bodies in a form it can best utilise or excrete.

      Aside from being supplied from an inferior source (because, yes, there are other, more bioavailable ways to supplement iron in our diet), there are health issues associated with the consumption of too much iron, from constipation to liver and heart problems.

      While coating of the filings may no longer occur, as you say, blanket supplementation is just one of many reasons I choose not to eat processed cereals.

      H ๐Ÿ™‚


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s