Cast iron safety/iron overload

[Pointedstick]

TL;DR version:

1. A healthy body does not absorb more iron than it needs if excess iron is consumed.
2. The body constantly loses small amounts of iron through normal processes of sweating and cell replacement (to say nothing of menstruation and other forms of blood loss), so excess iron that the body mistakenly absorbs will eventually dissipate.
3. Pre-menopausal women have really no reason to worry about this because they regularly lose blood through menstruation; men and post-menopausal women who are worried can artificially do the same thing by regularly donating blood (which is a nice thing to do, anyway).
4. Consuming extra calcium, zinc, and magnesium will naturally lower iron absorption if don't even want the iron to get into your body in the first place.
5. Between 0.3% and 0.8% of the caucasian population suffers from a genetic iron absorption disorder, invalidating the above; they should not use cast iron to cook (they should also not do a whole host of other things, too).

So I don't see any particular reason to be worried.


Long version:

Information taken from https://en.wikipedia.org/wiki/Human_iron_metabolism.

Iron is an absolute requirement for most forms of life, including humans and most bacterial species. Plants and animals all use iron; hence, iron can be found in a wide variety of food sources.

Iron is essential to life due to its unusual flexibility to serve as both an electron donor and acceptor.

Iron can also be potentially toxic. Its ability to donate and accept electrons means that if iron is free within the cell, it can catalyze the conversion of hydrogen peroxide into free radicals. Free radicals can cause damage to a wide variety of cellular structures, and ultimately kill the cell. To prevent that kind of damage, all life forms that use iron bind the iron atoms to proteins. This binding allows cells to benefit from iron while also limiting its ability to do harm.

[...]

In response to a systemic bacterial infection, the immune system initiates a process known as iron withholding. If bacteria are to survive, then they must obtain iron from their environment. Disease-causing bacteria do this in many ways, including releasing iron-binding molecules called siderophores and then reabsorbing them to recover iron, or scavenging iron from hemoglobin and transferrin. The harder they have to work to get iron, the greater a metabolic price they must pay. That means that iron-deprived bacteria reproduce more slowly.

[...]

Most of the iron in the body is hoarded and recycled by the reticuloendothelial system, which breaks down aged red blood cells. However, people lose a small but steady amount by gastrointestinal blood loss, sweating and by shedding cells of the skin and the mucosal lining of the gastrointestinal tract. The total amount of loss for healthy people in the developed world amounts to an estimated average of 1 mg a day for men, and 1.5–2 mg a day for women with regular menstrual periods. People with gastrointestinal parasitic infections, more commonly found in developing countries, often lose more.

This steady loss means that people must continue to absorb iron. They do so via a tightly regulated process that under normal circumstances protects against iron overload.

[...]

Iron uptake is tightly regulated by the human body, which has no regulated physiological means of excreting iron. Only small amounts of iron are lost daily due to mucosal and skin epithelial cell sloughing, so control of iron levels is mostly by regulating uptake. Regulation of iron uptake is impaired in some people as a result of a genetic defect that maps to the HLA-H gene region on chromosome. In these people, excessive iron intake can result in iron overload disorders, such as hemochromatosis.

[...]

Hemochromatosis is estimated to cause disease in between 0.3 and 0.8% of Caucasians.

[...]

Iron toxicity results when the amount of circulating iron exceeds the amount of transferrin available to bind it, but the body is able to vigorously regulate its iron uptake. Thus, iron toxicity from ingestion is usually the result of extraordinary circumstances like iron tablet over-consumption rather than variations in diet.

[...]

Iron absorption from diet is enhanced in the presence of vitamin C and diminished by excess calcium, zinc, or magnesium

Assuming all this information is accurate, I see no reason to be worried about cooking with cast iron. Iron is not a toxin; it is a mineral that is necessary for life itself that is only dangerous in excess quantities, which is why my body has a complicated mechanism for making sure it doesn't get too much of it, and which I have no reason to believe is not functioning normally.

[MachineGhost]

That's funny, I would swear we had this conversation a couple of years ago.

EDIT: This must be it...  http://gyroscopicinvesting.com/forum/ot ... e-concern/

[Pointedstick]

I want to bring up something from the other thread:

But in supplements or food, we're talking about organic ferrous iron which is iron in the natural state.  The type of iron used in cast-iron pots/pans is inorganic and already oxidized, i.e. toxic.

This doesn't make sense to me. By "oxidized iron", do you mean rust? My cast iron isn't rusty, and it's still very ferrous. Can you clarify the physical and/or nutritional differences between dietary iron and metallic iron?

[MachineGhost]

This doesn't make sense to me. By "oxidized iron", do you mean rust? My cast iron isn't rusty, and it's still very ferrous. Can you clarify the physical and/or nutritional differences between dietary iron and metallic iron?

I'm no chemist but look at this: https://en.wikipedia.org/wiki/Iron#Chem ... _compounds
I believe cast iron is type 3.

Yet, the differences seem irrelevant because of this:

Large amounts of ingested iron can cause excessive levels of iron in the blood. High blood levels of free ferrous iron react with peroxides to produce free radicals, which are highly reactive and can damage DNA, proteins, lipids, and other cellular components. Thus, iron toxicity occurs when there is free iron in the cell, which generally occurs when iron levels exceed the capacity of transferrin to bind the iron. Damage to the cells of the gastrointestinal tract can also prevent them from regulating iron absorption leading to further increases in blood levels. Iron typically damages cells in the heart, liver and elsewhere, which can cause significant adverse effects, including coma, metabolic acidosis, shock, liver failure, coagulopathy, adult respiratory distress syndrome, long-term organ damage, and even death.[90] Humans experience iron toxicity above 20 milligrams of iron for every kilogram of mass, and 60 milligrams per kilogram is considered a lethal dose.[91] Overconsumption of iron, often the result of children eating large quantities of ferrous sulfate tablets intended for adult consumption, is one of the most common toxicological causes of death in children under six.[91] The Dietary Reference Intake (DRI) lists the Tolerable Upper Intake Level (UL) for adults as 45 mg/day. For children under fourteen years old the UL is 40 mg/day.

However, ingesting inroganic iron doesn't seem any smarter to me than eating seafloor rocks to get calcium, although maybe you can make the argument that inorganic iron is even harder to absorb, which may generally be true because iron supplements cause severe constipation and are poorly absorbed.  So I may have been conflating ferrous iron with chelated iron, which is the normal state found in plants.  I don't know what state it is in animal flesh.

And this is why you should not supplement with iron whether from supplements or cast-iron:

Iron uptake is tightly regulated by the human body, which has no regulated physiological means of excreting iron.

In other words, iron levels can build up over time in anyone but menstruating women; accelerated by supplementing.  This is one case where supplementing is a clear contraindication unless ferritin levels are low (below 50).  Iron is truly nasty stuff.  Just look at how easily it rusts!

[Benko]

PS,

I haven't read anything new on this topic in a decade.

The fact that one can regularly donate blood to prevent harmful effects means there is nothing to be concerned about?

If you cook tomato products/any foods which are acidic you will likely increase the amount of iron absorbed.

I use simple high quality stainless steel pans most of the time.

[fnord123]

So I went though and read the old thread and this one.  It seems like as long as you don't use highly acidic foods in cast iron, and don't allow your pan to get rusty, and don't have some sort of blood disorder, that cast iron pans are perfectly good to use (and certainly better than anything that has Teflon involved).  Did I miss any scientific studies that show otherwise? 

[MachineGhost]

So I went though and read the old thread and this one.  It seems like as long as you don't use highly acidic foods in cast iron, and don't allow your pan to get rusty, and don't have some sort of blood disorder, that cast iron pans are perfectly good to use (and certainly better than anything that has Teflon involved).  Did I miss any scientific studies that show otherwise?

Specificaly from cast iron pans?  I'm not aware of any (who's got the time or money to do that for decades?).  From iron itself, yes.

[Pointedstick]

I'm no chemist but look at this: https://en.wikipedia.org/wiki/Iron#Chem ... _compounds
I believe cast iron is type 3.

That's interesting. I'll have to look into this more.

Yet, the differences seem irrelevant because of this:

Large amounts of ingested iron can cause excessive levels of iron in the blood.

Right, large amounts. Elsewhere I read that the body is capable of regulating the amount of uptake from any given iron input, but not shutting it off entirely. So every time you eat anything with iron in it (such as meat, vegetables, and fruits ) your body is absorbing some iron. This explains why iron toxicity can be caused by super-excessive ingestion such as guzzling iron supplements: the body has to absorb some, but even a small percentage of "a ridiculous amount" may still be "way too much."

If you're avoiding eating cast-iron-cooked tomato sauce or vinegar every day, cast iron cooking is not adding anywhere near enough iron into your diet that a healthy body is unable to reject it. Interestingly, according to NIH, you are more likely to overdose on iron (recommendation of of 8mg for an adult man) from eating breakfast cereals (18mg)!

By contrast, according to the Journal of the American Dietetic Association, even cooking spaghetti in tomato sauce in cast iron results in only 5.7 mg of iron! So even doing it wrong result in less iron than eating iron-fortified grain products.

The bottom line here is that the argument against cast iron cookware shouldn't concern the minute amount of iron that gets into the food, since if your body is healthy, it shouldn't matter. The real objection, to me, is your point that metallic cast iron is in a higher state of oxidation than dietary iron, which seems like it may be true and warrants more research. If this is true, than introducing iron into your body from cast iron cooking is responsible for increasing (even by a small amount) the oxidation level of the iron your body utilized for its metabolic reactions.

And this is why you should not supplement with iron whether from supplements or cast-iron:

Iron uptake is tightly regulated by the human body, which has no regulated physiological means of excreting iron.

In other words, iron levels can build up over time in anyone but menstruating women; accelerated by supplementing.

I don't believe that's true. First of all, it says there is no regulated means. As the article points out elsewhere, iron is constantly being removed through sweat, and regeneration of skin and gastrointestinal linings. Second, the body regulates the amount it absorbs in the first place; unless you are taking ludicrous quantities of iron or have Hemochromatosis, your body will be able to avoid inadvertently absorbing too much iron and the excess will simply get pooped or peed out.

This is one case where supplementing is a clear contraindication unless ferritin levels are low (below 50).  Iron is truly nasty stuff.  Just look at how easily it rusts!

My cast iron skillets have never rusted. Lots of iron doesn't rust easily. Look at all the wrought-iron fences and such in wet places that are hundreds of years old with no rust. It all depends on the chemical composition.


Again, the legitimate concern here seems to be that cooking with cast iron is introducing a source of more highly-oxidized iron into your body, not that it will cause your iron levels to get too high. If this is actually true, I wonder how big a deal it is.

[Mountaineer]

Seems to me if one seasons the cast iron effectively, which is needed for the non-stick property, the food is not in contact with the iron anyway - the food is in contact with polymerized flaxseed oil (or whatever type oil/grease is used).  What am I missing?  This worry of iron toxicity from a miniscule amount of iron in the food from using cast iron really seems like much ado about nothing to me.  But what do I know, I'm only a lowly chemical engineer and engineers tend to worry about the practical, not the theoretically possible 1 in a trillion case. 

... Mountaineer

[MachineGhost]

IDA = iron-deficiency anaemia.

Conclusion There is no evidence that iron cooking pots are effective against IDA. Further research is warranted to determine whether the iron leached from the pots is bioavailable.

http://journals.cambridge.org/action/di ... 0007001139

Diet Group members significantly increased their intake of flesh foods, heme iron, vitamin C and foods cooked using cast-iron cookware and significantly decreased their phytate and calcium intakes. Serum ferritin increased in the Supplement and Diet Groups by 59% (p=0.001) and 26% (p=0.068), respectively, in comparison to the Placebo Group. The serum transferrin receptor:serum ferritin ratio decreased by 51% in the Supplement Group (p=0.001), and there was a non-significant decrease of 22% (p=0.1232) in the Diet Group.

http://www.ncbi.nlm.nih.gov/pubmed/11601562

Conclusions: The Framingham Heart Study cohort is an iron-replete elderly population with a high prevalence of elevated iron stores in contrast with a low prevalence of iron deficiency, with insignificant effects of chronic disease on these iron status estimates. The likely liability in iron nutriture in free-living, elderly white Americans eating a Western diet is high iron stores, not iron deficiency.

http://ajcn.nutrition.org/content/73/3/638.long

[Benko]

one can discuss theory all one likes, but the answer here is simple:  get a blood test and see if your iron levels are elevated or not.

Speaking in general, we (the board, and people in general, some groups more than others)  get lost in theory, when the important thing is reality.

[Pointedstick]

IDA = iron-deficiency anaemia.

Conclusion There is no evidence that iron cooking pots are effective against IDA. Further research is warranted to determine whether the iron leached from the pots is bioavailable.

http://journals.cambridge.org/action/di ... 0007001139

Diet Group members significantly increased their intake of flesh foods, heme iron, vitamin C and foods cooked using cast-iron cookware and significantly decreased their phytate and calcium intakes. Serum ferritin increased in the Supplement and Diet Groups by 59% (p=0.001) and 26% (p=0.068), respectively, in comparison to the Placebo Group. The serum transferrin receptor:serum ferritin ratio decreased by 51% in the Supplement Group (p=0.001), and there was a non-significant decrease of 22% (p=0.1232) in the Diet Group.

http://www.ncbi.nlm.nih.gov/pubmed/11601562

The corollary to that would mean that it isn't available for uptake no matter its state of oxidation, no? In which case, there would be nothing to worry about! 

[MachineGhost]

The corollary to that would mean that it isn't available for uptake no matter its state of oxidation, no? In which case, there would be nothing to worry about! 

Yep, but there's still that 1mg.  Is it worth worrying about?  It may not have to be absorbed to do damage.

Benko is right, though.  Get a ferritin test.

[WildAboutHarry]

[quote=NIH]You get iron deficiency anemia when your body's iron stores run low. This can occur because:

You lose more blood cells and iron than your body can replace
Your body does not do a good job of absorbing iron
Your body is able to absorb iron, but you are not eating enough foods that contain iron
Your body needs more iron than normal (such as if you are pregnant or breastfeeding)

Bleeding can cause iron loss. Common causes of bleeding are:

Heavy, long, or frequent menstrual periods
Cancer in the esophagus, stomach, small bowel, or colon
Esophageal varices, usually from cirrhosis
The use of aspirin, ibuprofen, or arthritis medicines for a long time, which can cause gastrointestinal bleeding
Peptic ulcer disease

The body may not absorb enough iron in your diet due to:

Celiac disease
Crohn disease
Gastric bypass surgery
Taking too many antacids that contain calcium

You may not get enough iron in your diet if:

You are a strict vegetarian
You are an older adult and do not eat a full diet[/quote]

Asking cast iron cookware to offset heavy menstruation, cirrhosis, and these other things is a bit much. 

Can we agree that cast iron cookware:

1) Is durable
2) Does not contain toxic chemicals (at least US manufactured items)
3) Is inexpensive
4) MAY provide dietary iron

?

[MachineGhost]

1) Is durable
2) Does not contain toxic chemicals (at least US manufactured items)
3) Is inexpensive
4) MAY provide dietary iron

It's not dietary iron, but I think thats a different issue from it being bioavailabe.  I'm not impressed that it is, but I'm still wary of whatever it is you're actually ingesting.  Let's leave PS to it, shall we?  He's the chemical geek.

[WildAboutHarry]

[quote=University of Illinois at Urbana-Champaign]The following factors will increase the iron absorption from non-heme foods:

A good source of vitamin C (ascorbic acid) - i.e., oranges, grapefruits, tomatoes, broccoli and strawberries, eaten with a NON-HEME food
A HEME and NON-HEME food eaten together
A NON-HEME food cooked in an iron pot, such as a cast iron skillet[/quote]

No literature citation for the last item.

I know it is just a crappy state university.  But this is good enough for this state college grad.

[Pointedstick]

You can't win by cooking with metal, it seems. Typical Nickel-bearing stainless steels (ex. 18/8, 18/10, 304) will apparently leech Nickel when acidic foods are cooked in them:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284091/

After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After six hours of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34 fold and Cr increased approximately 35 fold from sauces cooked without stainless steel. Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, though significant metal contributions to foods were still observed. The tenth cooking cycle, resulted in an average of 88 ?g of Ni and 86 ?g of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage.

Nickel has no recognized biological use to humans, unlike Iron. And the food is coming into more contact with the stainless steel than any cast iron due to the seasoning, as Mountaineer pointed out. So you might be worse off cooking with stainless steel!

It looks like cooking in ceramic or nickel-less stainless steel (which can rust due to the lack of nickel) is the only way to go if you're really concerned about metal leeching.

Or, you could just stop worrying about it because the amounts of metal added to food, especially from older pots and pans, are probably completely insignificant.

[WildAboutHarry]

[quote=MangoMan]UIUC [my alma mater] is considered a top notch school in both Engineering and Agriculture. IDK  about biochemistry.[/quote]

I should have inserted a smiley  after the "crappy" line.  My folks hail from Peoria, so I probably would have attended one if the IL schools if they hadn't migrated to CA.

And didn't it used to be Champaign-Urbana?

[Pointedstick]

UIUC [my alma mater] is considered a top notch school in both Engineering and Agriculture. IDK  about biochemistry.

I should have inserted a smiley  after the "crappy" line.  My folks hail from Peoria, so I probably would have attended one if the IL schools if they hadn't migrated to CA.

And didn't it used to be Champaign-Urbana?

Locals refer to it as Champaign-Urbana even though it's UIUC, not UICU. Not sure why.

[Mountaineer]

It looks like cooking in ceramic or nickel-less stainless steel (which can rust due to the lack of nickel) is the only way to go if you're really concerned about metal leeching.

Good grief, Pointedstick, now you have gone and endorsed yet another type of potential poisoning!  Now I can't cook in anything!  Lawsuit alert!  I can't even even eat fresh fruit and vegetables as nuke dust rainwater fell on it and uncooked animal meat has iron contaminated blood.

"Some ceramics are composed of only two elements. For example, alumina is aluminum oxide, Al2 O3 ; zirconia is zirconium oxide, ZrO 2 ; and quartz is silicon dioxide, SiO 2 . Other ceramic materials, including many minerals, have complex and even variable compositions. For example, the ceramic mineral feldspar, one of the components of granite, has the formula KAlSi 3 O 8 .

The chemical bonds in ceramics can be covalent, ionic, or polar covalent, depending on the chemical composition of the ceramic. When the components of the ceramic are a metal and a nonmetal, the bonding is primarily ionic; examples are magnesium oxide (magnesia), MgO, and barium titanate, BaTiO 3 . In ceramics composed of a metalloid and a nonmetal, bonding is primarily covalent; examples are boron nitride, BN, and silicon carbide, SiC. Most ceramics have a highly crystalline structure, in which a three-dimensional unit, called a unit cell, is repeated throughout the material. For example, magnesium oxide crystallizes in the rock salt structure. In this structure, Mg 2+ ions alternate with O 2? ions along each perpendicular axis."

... Mountaineer

[Benko]

You can't win by cooking with metal, it seems. Typical Nickel-bearing stainless steels (ex. 18/8, 18/10, 304) will apparently leech Nickel when acidic foods are cooked in them:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284091/

After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After six hours of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34 fold and Cr increased approximately 35 fold from sauces cooked without stainless steel. Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, though significant metal contributions to foods were still observed. The tenth cooking cycle, resulted in an average of 88 ?g of Ni and 86 ?g of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage.

Nickel has no recognized biological use to humans, unlike Iron. And the food is coming into more contact with the stainless steel than any cast iron due to the seasoning, as Mountaineer pointed out. So you might be worse off cooking with stainless steel!

It looks like cooking in ceramic or nickel-less stainless steel (which can rust due to the lack of nickel) is the only way to go if you're really concerned about metal leeching.

Or, you could just stop worrying about it because the amounts of metal added to food, especially from older pots and pans, are probably completely insignificant.

1. FROM WEBMD web sites for doctors, so you know they are super conservative on anything nutritional
http://www.webmd.com/vitamins-supplemen ... ame=NICKEL

1. Nickel is a mineral. It is found in several foods including nuts, dried beans and peas, soybeans, grains, and chocolate. The body needs nickel, but in very small amounts. Nickel is a common trace element in multiple vitamins.

Nickel is used for increasing iron absorption, preventing iron-poor blood (anemia), and treating weak bones (osteoporosis).

How does it work?
Nickel is an essential nutrient in some chemical processes in the body. Its precise functions in the body are not known.

2.  "After six hours of cooking"
Since my current use of stainless steel cookware does not involve any cooking of more than 45 min, and does not involve tomato products I'll rest easy.

3.  The "tomato sauce" I buy is commercial but locally made, and I'll try not to think too much about what kinds of pans/pots they use.

[MachineGhost]

Great find on the toxicity of stainless steel cookware, PS!  That's some scary amounts of nickle and chromium leeching out.  Compared to 1mg of Type3 from cast iron.

3.  The "tomato sauce" I buy is commercial but locally made, and I'll try not to think too much about what kinds of pans/pots they use.

I assume it comes in a glass jar?  Because cans are nickel and/or lined with BPA!  The BPA is in response to nickle leeching into food, or was it lead?  Can't remember.  But now BPA is arguably a cure worse then the disease.

[Benko]

Yup, glass jar.

[MachineGhost]

[quote=http://www.eurekalert.org/pub_releases/ ... 011415.php]It's been known for decades that some metals, including iron, accumulate in human tissues during aging and that toxic levels of iron have been linked to neurologic diseases, such as Parkinson's. Common belief has held that iron accumulation happens as a result of the aging process. But research in the nematode C. elegans in the Lithgow lab at the Buck Institute shows that iron accumulation itself may also be a significant contributor to the aging process, causing dysfunction and malfolding of proteins already implicated in the aging process. The research is online in Aging

Similar to what happens in humans and other mammals, researchers found that levels of calcium, copper, iron and manganese increased as the worms aged. But iron accumulated much more than the others, said Buck faculty Gordon Lithgow, PhD, senior scientist on the project. "We were drawn to iron because there is all this literature that links excess iron to Alzheimer's and Parkinson's."

Researchers began manipulating the nematode's diet. "We fed iron to four day-old worms, and within a couple of days they looked like 15 day-old worms," said Lithgow. "Excess iron accelerated the aging process." Lithgow says excess iron is known to generate oxidative stress and researchers expected to see changes in the worm based on that toxicity. "Instead, what we saw looked much more like normal aging," said Lithgow. "The iron was causing dysfunction and aggregation in proteins that have already been associated with the aging process. Now we're wondering if excess iron also drives aging. "

Researchers, led by graduate student Ida Klang, also treated normal nematodes with the FDA-approved metal chelator CaEDTA - a drug that's used in humans at risk for lead poisoning. The drug slowed age-related accumulation of iron and extended the healthspan and lifespan of the nematodes. Klang also gave the drug to worms genetically bred to develop specific protein aggregations implicated in human disease. The chelator was also protective in those animals.

Lithgow says the work has implications for the aging research field. "Maintaining the proper balance of metals is key to good health throughout the lifespan, and it's pretty obvious that this delicate balance can go off-kilter with age," he said. "This is a phenomena that has not been extensively studied by aging researchers and it's an area that has potential for positive exploitation." As far as the general public is concerned, Lithgow was quick to warn people away from taking CaEDTA and other available metal chelators as anti-aging medication. "CaEDTA has a very blunt mechanism of action and is associated with dangerous side effects in humans and the track record for other chelators is not well established," said Lithgow, who urged people to talk to their physicians about the use of iron supplementation, especially for postmenopausal women. [/quote]

I'm having my ferritin levels tested in a few days.  Should be interesting.

[fnord123]

Nickel is bad stuff too - some studies show as much as 14.5% of some populations have bad reactions to it (cite: http://www.medscape.com/viewarticle/572961).  This is a much higher rate than that of people with deficiencies in processing iron.