Iron Supplements Review (Iron Pills, Liquids and
Gummies)
Find the Best Iron
Supplement. See Which Iron Supplements Passed or Failed Our Tests and Which Are
Our Top Picks.
Medically reviewed and
edited by Tod Cooperman, M.D. 
Last Updated
: 09/21/2021 | Initially Posted:
12/28/2017Latest Update: Iron Dose Falls
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Table of Contents
Summary
What is iron? Iron is essential to manufacture
hemoglobin, which enables red blood cells to transfer oxygen to the body's
tissues. It is widely available in foods including meat, fish, grains and
vegetables and the average diet provides sufficient iron (See What It Is).
Symptoms of iron deficiency: Iron deficiency (which is treatable
with iron supplements) can cause symptoms such as fatigue, shortness of breath,
dizziness, headache and pale skin. It is most common in menstruating women but
also is commonly seen in children and pregnant women (few men are deficient in
iron, and some may be at risk for iron excess).
Iron supplementation may reduce unexplained fatigue in women of
child-bearing age who are not anemic but have ferritin levels in the
lower end of normal range, inhibit dry cough associated with ACE inhibitors,
and help to reduce symptoms of restless leg syndrome in people with low
ferritin levels (see What It Does).
Which form of iron is best? Iron comes in many chemical forms and
formulations, including pills, liquids, and gummies. If taken with just water,
all are about equally well-absorbed, so less expensive forms, such as ferrous
sulfate, are fine. However, with larger doses, some people experience gastric
discomfort and/or constipation. Taking with food may reduce discomfort, but
also reduces absorption of certain forms of iron, such as ferrous sulfate,
while other forms are better absorbed in the presence of food, such ferrous bisglycinate and ferrous glycinate. Note that some
supplements include vitamin C to increase iron absorption but this is unlikely
have a significant effect, and there is concern that slow- or timed-release
products may lead to reduced absorption of iron (see Forms of Iron and Avoiding Stomach Upset).
Best iron supplements: One product was Not Approved for failing to
disintegrate within the required time (See What CL Found). Among the products that passed
testing and were "Approved" for their quality, CL selected its Top Picks based on quality, cost,
dose, and absorption.
How much iron to take, safety and side effects: For correcting
iron-deficiency anemia in adults: 100 mg to 200 mg daily, divided into two or
three separate doses; this should be done only under physician supervision.
When used as a treatment for other conditions, doses between 40 mg and 250 mg
have been used. Unless treating a deficiency or specific condition, limit your
daily intake of iron from supplements and fortified foods to no more than 45 mg
to avoid side-effects and the harmful effects of excessive iron. Iron can also
interfere with certain drugs. (See How much to take? and Concerns and Cautions).
Don't take iron with tea, as well as other minerals, as this may decrease iron
absorption (see What to avoid when taking).
What It Is:
Iron is
an essential mineral that the body requires in small amounts. It is widely
available in foods including meat, poultry, and fish, as well as dried fruits,
grains, and green leafy vegetables. Iron from plant sources is absorbed half as
well as that from animal sources. The average diet provides about 10 to 20 mg
of iron per day.
What It Does:
Iron Deficiency and Anemia
Iron is needed to manufacture hemoglobin, which enables red blood cells to
transfer oxygen to the body's tissues. Severe or prolonged iron deficiency is
the leading cause of anemia in the United States, affecting about five percent
of women and two percent of men. Symptoms of iron deficiency anemia include
easy fatigability, shortness of breath, dizziness, headache, coldness of hands
and feet, pale skin, chest pain, weakness, and lethargy. Other symptoms can
include brittle nails, swelling or soreness of the tongue, cracks in the sides
of the mouth, loss of taste, an enlarged spleen, and frequent infections. Iron
deficiency has also been associated with recurrent aphthous stomatitis (canker
sores) (Akintoye, Dent Clin North Am 2014).
Some people with iron-deficiency anemia develop restless legs syndrome (see
more about this in Benefits of Correcting Iron Deficiency below). Iron
deficiency anemia can also cause irregular heartbeats (arrhythmias), a heart
murmur, an enlarged heart, and heart failure (Kettaneh, Appetite
2005; NIH, 2014).
Iron deficiency is most common in menstruating women but also is commonly seen
in children and pregnant women. According to the CDC, 9.5% of women 12 - 29 years are
deficient, as are 6.7% of children ages 1 to 5. There are higher rates of iron
deficiency in Mexican-American children aged 1 to 5 years (11%) and in
non-Hispanic black (16%) and Mexican-American women (13%) of childbearing age
(12 to 49 years) when compared to other race/ethnic groups. Low iron levels
also may result from excessive bleeding, burns, and hemodialysis, as well as
stomach and intestinal problems. Drugs that reduce stomach acid may also impair
iron absorption (see What to avoid when taking).
Iron-deficiency anemia is one of the most common
deficiencies in people with Crohn's disease and other forms of
inflammatory disease (IBD). This may be treated with iron supplements,
although in some cases, intravenous or prescription iron may be recommended (Crohn's and Colitis Foundation 2017).
A particular form of iron known as ferric maltol (Accrufer,
Feraccru) that is only available by prescription has
been shown to be tolerable and effective in treating iron-deficiency anemia in
people with Crohn's or other inflammatory bowel disease who were unable to
tolerate other forms of iron, such as ferrous gluconate, ferrous succinate, and
ferrous sulfate (Weisshof, Curr Opin Clin Nutr Metab Care 2015).
During pregnancy, iron deficiency can result in preterm delivery and
low-birth-weight babies.
Among children, iron deficiency is most common from ages 6 to 24 months, where
it can cause developmental and behavioral problems. If iron deficiency is
extremely severe, some of these problems can be irreversible.
Although few men are deficient in iron, 29% are at-risk
for iron excess (CDC 2012).
Benefits of Correcting Iron Deficiency
Some evidence suggests that even mild iron deficiency, too mild to cause
anemia, may cause fatigue and impair sports performance. Iron supplementation
has been shown to reduce unexplained fatigue in women of child-bearing
age who are not anemic but have ferritin levels in the lower end of
normal range (less than 50 ug/L) (ferritin is an indicator of total iron stored
in the body). A 12-week study of 198 such women (ages 18 to 53) found that
those who received 80 mg of iron from ferrous sulfate daily from a time-release
pill experienced a 47.7% decrease in fatigue, compared to a 28.8% decrease in
the placebo group — a significant difference (Vaucher, CMAJ 2012), although there was no
significant effect on anxiety or depression. Ferritin levels increased by 11.4
ug/L compared with placebo.
Among blood donors with normal hemoglobin levels, low-dose
iron supplementation (37.5 mg of iron as ferrous gluconate daily) reduces the time
by more than half for hemoglobin and ferritin levels to recover after donating
a unit of blood. A study showed that those receiving iron recovered most of
their decrease within about 30 days versus 78 to 158 days for those not
receiving iron, depending on whether their ferritin levels were initially high
or low. For those getting the iron supplement, ferritin levels returned to
normal within 76 days while 67% of those not receiving supplementation had not
fully recovered iron stores after 168 days -- when the study ended (Kiss, JAMA 2015). The
researchers noted that although the hemoglobin decrease after donation is
relatively small (about 10%) and of marginal clinical significance, for
frequent donors it is important to be recovered before the next donation;
suggesting that the current waiting period of 8 weeks (56 days) in the U.S. may
be too short.
Verbal learning and memory have been shown to improve when
adolescent girls with iron deficiency (although not anemia) are treated with
iron supplementation (Bruner, Lancet 1996).
Unfortunately, among patients with heart failure and iron
deficiency, giving high-dose iron (150 mg as iron polysaccharide) twice daily
for 16 weeks did not improve peak oxygen uptake nor exercise capacity (6-minute
walking distance) and only minimally improved iron levels (a 3% increase). A
possible reason for the failure (which was not expected, as iron given
intravenously in such patients raises iron by about 70%), was abnormally high
blood levels in these people of hepcidin, an iron regulatory
hormone that lowers iron levels by reducing iron absorption and trapping iron
in while blood cells and liver cells (Lewis, JAMA 2017).
People with low or deficient levels of iron may be more likely
to suffer from restless legs syndrome (Trotti, Cochrane
Database Syst Rev 2019). Guidelines from the American Academy
of Neurology advise that taking 65 mg of iron (from 325 mg ferrous sulfate) and
200 mg vitamin C (to help with iron absorption) twice daily may improve
symptoms in individuals with restless legs syndrome who have ferritin levels
below 75 ng/mL (Winkelman, Neurology 2016).
This recommendation is based on a small study that gave a similar treatment
(although half the vitamin C: 100 mg twice daily) to older men and women with
low-normal blood ferritin levels (15 - 75 ng/mL) for three months. The severity
of restless legs symptoms decreased by an average of 10 points on a scale of 0
to 40, while it decreased by just 1 point among those who took a placebo (Wang, Sleep Med 2009).
Overall quality of life, however, did not improve in either group. Taking the
iron increased blood ferritin levels from an average of 40 ng/mL to 65 ng/mL. [Note: The rationale for taking vitamin C with
iron has been that vitamin C increases iron absorption, but any clinical effect
may be insignificant. See ConsumerTips™ for
more details.]
Be aware that restless legs syndrome may also occur as a result of hereditary
hemochromatosis (a disorder in which too much iron is absorbed
from the diet and ferritin blood levels can get too high), and this
treatment would not seem appropriate in such a situation (Cotter, Ther Clin Risk Manag 2006).
Other Uses
Iron supplements have shown some promise for reducing the dry
cough caused by drugs in the angiotensin-converting enzyme inhibitor
family (ACE inhibitors) (Lee, Hypertension 2001).
A small study of iron in children with ADHD showed improvement
in some symptoms comparable to that with stimulant medicines (Konofal, Pediatr Neurol 2008).
A lower risk of suffering PMS (premenstrual
syndrome) has been associated with a high intake of iron (over 20 mg per day)
from supplements or plant-based foods (as opposed to meats) (Chocano-Bedoya, Am J Epidem
2013). Compared to women with the lowest daily intakes of
iron (median of 9.4 mg) from these sources, the risk of PMS was reduced by 29%
among those with a median intake of 21.4 mg, and by 36% among those with a
median intake of 49.2 mg. Interestingly, the same study found that women
consuming higher amounts of potassium from their diet (median intake of 3,717
mg daily) had a higher risk of PMS than those consuming less
potassium.
Iron deficiency has been associated with an increased risk
of fibromyalgia (widespread muscle pain and fatigue) in women.
A study in Taiwan found that women (ages 18 and older, average age 50) with
iron deficiency anemia had a 22% increased risk of fibromyalgia compared to
women without iron deficiency anemia, but there was no increased risk for men.
When people with iron deficiency anemia were receiving iron supplementation,
their risk of fibromyalgia was 21% lower than those who received no iron
therapy. While this does not prove that iron deficiency causes fibromyalgia
in women or that iron supplementation treats fibromyalgia, the researchers
recommended that all people with fibromyalgia have their blood levels of iron
checked, and corrected with supplementation if needed (Yao, Sci Rep 2021).
See ConsumerTips™ for
information about the forms of iron in supplements and dosage.
Quality Concerns and
Tests Performed:
In
1997, the U.S. Food and Drug Administration (FDA) reported that several
iron-containing supplements had been recalled because of excessive levels of
lead. Subsequent testing by ConsumerLab.com similarly found some iron products
to be contaminated with lead -- a potentially harmful contaminant. However,
tests by ConsumerLab.com since 2011 have found few instances of lead
contamination, although some supplements have been discovered to contain less
than their claimed amounts of iron. Because no government agency is responsible
for routinely testing iron supplements for their contents or quality,
ConsumerLab.com independently evaluated iron products to determine whether they
contained the iron stated on their labels. Products containing whole herbs
and/or 250 mg or more of minerals per daily serving were also tested for
contamination with lead, cadmium and arsenic. Iron tablets and caplets that
were not chewable or time-release were additionally tested for their ability to
break apart ("disintegrate") as needed for absorption. (See Testing Methods and Passing Score.)
What CL Found:
Quality
Our tests found that most iron supplements were well made and contained the
iron they listed, so that 13 of the 14 products we selected for testing were
Approved for their quality, as were an additional 8 products tested in our
voluntary Quality Certification Program.
The one product that we selected for testing but failed to pass was Floradix Iron Tablets (10 mg). It contained
its listed amount of iron but the tablets failed to fully break apart in
disintegration testing within the required 30 minutes — they needed 60 minutes.
A concern with slower disintegration is that the ingredients may not be fully
available for absorption in the gut. All other regular tablets and caplets
fully disintegrated in less than 30 minutes or less.
Cost
We also compared products on the cost to obtain from each an equivalent amount
(25 mg) of iron (which is more than the recommended daily allowance but about
the mid-point in dosage among iron supplements). The cost to obtain 25 mg of
iron ranged from just $0.01 to over $2.00 -- a 200-fold difference. The least
expensive way to get iron was from high-dose products (i.e., those with 65 mg
of iron per unit) made of ferrous sulfate -- Member's Mark Iron and Nature
Made Iron, each of which cost only 3 cents per tablet. The last column in
the Results table below identifies the lowest
cost products for each type of iron.
Which iron supplement is best?
The iron supplement you select should provide:
·
the right dose of iron for the therapeutic use
for which you will be taking it
·
the right form of iron to allow good absorption
but be least likely to cause gastrointestinal side effects such as constipation
·
the best quality, i.e., be well made, properly
labeled, and Approved in our tests, and
·
the best value (i.e., the least cost for the
form of iron you've chosen)
Considering these
factors, we have made the following CL Top Picks (below) among
iron supplements Approved in our tests.
Top Picks:
CL's
overall Top Pick among iron supplements is NOW Iron which
provides 18 mg (the recommended daily allowance for women ages 19 — 50) of iron
per vegetarian capsule in the form of ferrous bisglycinate
for 6 cents. This form of iron has been shown to be absorbed two to four times
better than ferrous sulfate when taken with food, and may cause
less gastrointestinal discomfort than ferrous sulfate, ferrous fumarate, and
ferrous gluconate. In general, taking iron with food will help reduce
gastrointestinal discomfort that iron may cause.
However, if you have no trouble tolerating ferrous sulfate taken with just
water, you can spend less and take one of the ferrous sulfate supplements such
as Member's Mark Iron and Nature Made Iron, each
providing 65 mg of iron per 3 cent tablet. If you want a lower dose, use Fergon, which contains 27 mg of iron in the
gluconate form for 10 cents. In fact, to maximize absorption of iron,
regardless of form, it is best to take iron with just water. But if you need to
take iron with food or within an hour after eating, the bisglycinate
form is better absorbed.
Be aware that the amount of iron in NOW Iron (18 mg) is the
daily requirement for women who have not gone through menopause. It's not
enough, however, to correct an iron deficiency and, at the same time, it's more
than most children, adolescents, and men need on a daily basis.
If you need more iron and are unable to take it with water, our Top
Picks are other products with iron bisglycinate
-- Nature's Bounty Gentle Iron (8 cents per capsule providing
28 mg of iron) or Solgar Gentle Iron
25 mg (9 cents per vegetable capsule) which is also vegetarian and
Kosher.
Several timed-release or slow release products
were Approved (Ferro-Sequels, Jamieson, and Well at
Walgreens). While these are said to reduce gastric irritation from iron,
there is concern that, due to the slower release, less iron may be available in
the small intestine, which is where iron gets absorbed. Consequently, none of
these is among our Top Picks.
Several products include modest amounts of
vitamin C, ostensibly to boost iron absorption, but it's unlikely that this helps much, so is not worth
paying more for the vitamin C.
Test Results by Product:
Listed
alphabetically below are the test results for 22 iron products. ConsumerLab.com
selected 14 of these products. Eight other products (indicated with a CL flask)
were tested at the request of their manufacturers/distributors through ConsumerLab.com's voluntary Quality Certification Program,
and are included for having passed testing.
Shown for each product is the labeled amount of elemental iron per unit, the
daily number of servings recommended on the label, the expected dosage of iron
per day based on that recommendation, and the form of iron listed on the label.
The calculated cost to obtain 25 mg of iron is provided in the last column
along with the price per serving, price paid, and additional key ingredients
and special dietary designations.
The full list of ingredients is available for each product by clicking on the
word "Ingredients" in the first column. All the "Approved"
products met their label claims for iron, met FDA labeling requirements, and,
non-chewable and non-time-release tablets and caplets were shown to break apart
properly. In addition, Approved products containing whole herbs and/or 250 mg
or more of minerals per daily serving did not exceed contamination limits for
lead, cadmium or arsenic.
Many of the products are designed for treating iron deficiency and, therefore,
exceed the Recommended Dietary Allowance (RDA) as well as the upper level (UL)
of tolerable intake for iron. Those exceeding the UL are footnoted alongside
their Approval status. Under a physician's supervision it's acceptable to
exceed these limits, because the potential consequences of untreated iron
deficiency may be more severe than the potential.
|
RESULTS OF CONSUMERLAB.COM TESTING OF IRON SUPPLEMENTS |
|||||||
|
Product Name, Amount
Listed of Iron per Unit, Serving Size, and Suggested Daily Serving on Label |
Claimed Amount Iron
Per Labeled Daily Serving |
--TEST RESULTS-- |
Cost For Daily
Suggested Serving On Label |
||||
|
OVERALL RESULTS: |
Contained Labeled
Amount of Iron |
Did Not Exceed
Contamination Limit for Lead, Cadmium and Arsenic1 |
Disintegrated
Properly |
||||
|
|
25 mg |
APPROVED |
|
NA |
NA |
$0.10 |
|
|
|
28 mg |
APPROVED |
|
NA |
|
$0.49 |
|
|
|
27 mg |
APPROVED |
|
NA |
|
$0.10 |
|
|
|
65 mg3 |
APPROVED |
|
NA |
NA |
$0.26 |
|
|
|
20 mg |
NOT APPROVED |
|
NA |
Did not fully
disintegrate in 30 minutes |
$0.52 |
|
|
|
10 mg |
APPROVED |
|
|
NA |
$0.90 |
|
|
|
18 mg |
APPROVED |
|
NA |
NA |
$0.11 |
|
|
|
50 mg3 |
APPROVED |
|
NA |
NA |
$0.16 |
|
|
|
15 mg |
APPROVED |
|
NA |
NA |
$0.20 |
|
|
|
65 mg3 |
APPROVED |
|
NA |
|
$0.03 |
|
|
|
65 mg3 |
APPROVED |
|
NA |
|
$0.03 |
|
|
|
28 mg |
APPROVED |
|
NA |
NA |
$0.08 |
|
|
|
15 mg |
APPROVED |
|
NA |
NA |
$0.22 |
|
|
|
18 mg |
APPROVED |
|
NA |
NA |
$0.06 |
|
|
|
65 mg3 |
APPROVED |
|
NA |
|
$0.05 |
|
|
|
25 mg |
APPROVED |
|
|
NA |
$0.11 |
|
|
|
25 mg |
APPROVED |
|
NA |
NA |
$0.09 |
|
|
|
65 mg3 |
APPROVED |
|
NA |
|
$0.07 |
|
|
|
18 mg |
APPROVED |
|
|
NA |
$0.11 |
|
|
|
15 mg |
APPROVED |
|
NA |
NA |
$0.24 |
|
|
|
45 mg4 |
APPROVED |
|
NA |
NA |
$0.17 |
|
|
|
18 mg |
APPROVED |
|
NA |
NA |
$0.25 |
|
|
|
|||||||
|
Unless otherwise noted, information about the products
listed above is based on the samples purchased by ConsumerLab.com (CL) for
this Product Review. Manufacturers may change ingredients and label
information at any time, so be sure to check labels carefully when evaluating
the products you use or buy. If a product's
ingredients differ from what is listed above, it may not necessarily be of
the same quality as what was tested. |
|||||||
|
Copyright ConsumerLab.com, LLC, 2017. All rights reserved.
Not to be reproduced, excerpted, or cited in any fashion without the express
written permission of ConsumerLab.com LLC. |
|||||||
ConsumerTips™:
How
Much to Take?
To Treat Iron Deficiency and Anemia
Traditionally, a
typical recommended adult dosage for correcting iron-deficiency anemia has been
100 to 200 mg daily, divided into two or three separate doses, with the
specific recommended dose depending on the severity of the anemia and weight of
the individual. However, in September 2021, the British Society of
Gastroenterology revised its guidelines, recommending only 50 to 100 mg
of iron taken once daily on an empty stomach to correct iron deficiency.
This change was based on clinical evidence showing that a single 60-mg dose of
iron increased levels of hepcidin, a protein that blocks the absorption
of iron from subsequent doses. Consequently, absorption of iron from a
single 60-mg daily dose was found to be similar to two 60-mg doses taken the
same day. For people with significant gastrointestinal disturbance to oral iron
replacement therapy, the British Society of Gastroenterology recommends
switching to prescription-only ferric maltol (Accrufer),
following alternate day iron therapy, or receiving parenteral (i.e.,
injectable) iron. It does not recommend switching to a
different iron salt form (e.g., from ferrous sulfate to ferrous gluconate or
fumarate), as research does not appear to support this practice (Snook, Gut 2021). About
two months' time is usually required to restore hemoglobin levels. Many more
months of iron supplementation may be required to fully build up iron stores.
A dose of 80 mg of iron from ferrous sulfate given as a time-release pill daily
for 12 weeks has been used to treat unexplained fatigue in women who are not
anemic but have low ferritin levels (Vaucher, CMAJ 2012). (Note: A timed-release
pill Approved in this Review is Ferro-Sequels).
Some experts recommended taking iron along with vitamin C to
boost iron absorption. This recommendation stemmed from preliminary research
showing that vitamin C can boost iron absorption from a single meal.
However, other research found that iron absorption from a complete diet (i.e.,
several meals over several days) was not increased by vitamin C (Cook, Am J Clin Nutr 2001),
and a study in China suggested that vitamin C may not help when taking iron
supplements. The study in China among 440 people (average age 38) with iron
deficiency anemia found that those taking 100 mg of iron (as ferrous succinate)
three times daily after a meal increased levels of hemoglobin (an
iron-containing protein in the blood that carries oxygen and is low in people
with iron deficiency) at two-week follow-up by about the same amount as those
taking each dose of iron along with 200 mg of vitamin C. Also, at eight-weeks
follow-up, blood levels of ferritin (a storage form of iron in the blood), as
well as iron levels in the blood, increased by about the same amount whether or
not iron had been taken with vitamin C (Li, JAMA Netw Open 2020).
Based on this evidence, the British Society of Gastroenterology does not recommend
taking vitamin C along with iron (Snook, Gut 2021).
To Prevent Anemia
The daily recommended intake of iron for healthy individuals depends on your
gender and life stage. Most people are able to meet the requirement from their
diet, from foods such as meat, poultry, and fish, as well as from dried fruits,
grains, and green leafy vegetables. The average diet provides about 10 to 20 mg
of iron per day. Bear in mind that iron from plant sources is absorbed half as
well as that from animal sources. Consequently, vegetarians who exclude all
animal products from their diets may need almost twice as much dietary iron
each day as non-vegetarians. (Vegetarians should consider consuming plant
sources of iron along with a good source of vitamin C, such as citrus fruits,
to improve the absorption of iron from these foods).
The RDA (Recommended Daily Allowance) for iron is 7 mg for children ages 1 to 3
and 10 mg for children ages 4 to 8. It then decreases to 8 mg for children ages
9 to 13. For males ages 14 to 18, the RDA is 11 mg; 19 and older, it decreases
to 8 mg. For females, ages 14 to 18, the RDA is 15 mg; 19 to 50, it's 18 mg,
decreasing to 8 mg ages 51 and older.
Because of fetal needs, the RDA for pregnant women is 27 mg. For breast-feeding
women younger than age 18, the RDA is 10 mg; ages 19 and older, it's 9 mg.
Also, postmenopausal women taking hormone replacement therapy should consume
more iron because the therapy can cause periodic uterine bleeding. Oral
contraceptives may reduce menstrual blood loss, so women taking them may need
less daily iron.
The FDA requires that dietary supplements state on their labels the % Daily
Value for certain vitamins and minerals. However, this is based on an average
and may not be appropriate for you, so use the RDAs above. When reading labels,
remember that 1,000 mcg (micrograms) equals 1 mg (milligram) and that 1,000 mg
equals 1 gram.
For Other Uses (see What It Does section for clinical
information)
To improve cognitive function in non-anemic, iron deficient adolescent
girls, 130 mg of iron (as 650 mg of ferrous sulfate) given twice daily
has been used (Bruner, Lancet 1996).
To speed the recovery of hemoglobin and ferritin levels after blood
donation, 37.5 mg of iron (as ferrous gluconate) has been used (Kiss, JAMA 2015).
To inhibit dry cough associated with ACE inhibitors, 51.2 mg of
iron daily (as 256 mg of ferrous sulfate) has been used (Lee, Hypertension 2001).
To treat ADHD in children (aged 5 to 8) who are not anemic, 80
mg of iron daily (given as ferrous sulfate) has been used (Konafal, Pediatr Neurol 2008).
Upper limit -- Don't take too much!
High daily amounts of iron can cause gastrointestinal distress, especially when
iron supplements are consumed on an empty stomach, and there are additional
risks with long-term use of high-dose iron (see Concerns and Cautions). The Upper Tolerable
Intake Level (UL) is 40 mg for children younger than age 13 and 45 mg for
everyone else. However, these limits may be too high for people with hereditary
hemochromatosis who are at unique risk for accumulating harmful levels of iron.
Be aware that labels are unlikely to provide information indicating whether the
ingredients exceed tolerable intake levels -- the FDA doesn't require that
information.
Forms of Iron and Avoiding
Stomach Upset:
Several different forms
of iron are used in supplements. The actual amount of usable
"elemental" iron per milligram of iron compound varies depending on
the form. For example, 20% of ferrous sulfate is iron and only 12% of ferrous
gluconate is iron. Put another way, to get 50 mg of iron, you could take about
250 mg of ferrous sulfate or about 417 mg of ferrous gluconate. Fortunately,
the consumer doesn't need to do the calculations -- the manufacturer does this.
The usable amount or iron (elemental iron) is what appears in the Supplement
Facts panel on the label. Generally, the least expensive forms of iron are
ferrous sulfate, ferrous fumarate, and ferrous gluconate. If you have
trouble tolerating these forms of iron due to gastrointestinal discomfort,
consider ferrous bisglycinate, ferrous glycinate, or
iron amino acid chelates. [Ferric maltol also seems to be better tolerated,
although this form is available only by prescription.] One study showed ferrous
bisglycinate (also known as iron bis-glycinate or Ferrochel) to be absorbed two to four times better than
ferrous sulfate when given with food (Layrisse, J Nutr 2000), although it was not absorbed
better than ferrous ascorbate when given only with water (Olivares, Arch Latinoam Nutr 2001). Timed-release iron supplements may
also reduce gastrointestinal discomfort, but there is some concern that they
reduce iron absorption.
Some supplements contain heme-iron polypeptide or HIP, which
appears to be better absorbed than iron salts, such as ferrous sulfate. This
was shown in a study in which both HIP and ferrous sulfate were taken with
breakfast although the food ingested may have interfered with ferrous sulfate
absorption. Preliminary evidence suggests that HIP may also be better tolerated
than ferrous sulfate (Seligman, Nutrition Research 2000).
A branded version of HIP is Proferrin which is found
in Feosol Bifera in
this Review, which also includes another iron ingredient, polysaccharide-iron
complex or PIC. The absorption of PIC is about the same as ferrous sulfate, but
it is apparently tasteless and odorless and may cause less gastric irritation.
A study in infants and young children with nutritional
iron-deficiency anemia comparing equal, low-dose amounts of iron from ferrous
sulfate and PIC (as NovaFerrum) found ferrous sulfate
to increase hemoglobin levels slightly better PIC and completely resolve anemia
in more patients compared to PIC (29% vs 6%). Researchers had expected the
opposite. There were also fewer reports of diarrhea in these children with
ferrous sulfate than with PIC (35% vs 58%), although somewhat more reports of
vomiting with ferrous sulfate (58% vs 45%). The doses were given as liquid
drops at bedtime (Powers, JAMA 2017).
Preliminary research has shown that taking lactoferrin (a
protein in milk) with iron may help prevent sports anemia (a form of
iron-deficiency anemia) in athletes better than taking iron-only supplements.
One study in Japan among female long-distance runners found that taking tablets
providing 1.8 grams of lactoferrin plus 6 mg of iron (as ferric pyrophosphate)
daily during 8 weeks of training prevented a significant decline in blood
levels of iron compared to baseline, while taking iron-only supplements did not
(Koikawa, Biosci Biotechnol Biochem 2008).
Research has also shown that lactoferrin may help treat iron-deficiency anemia
in women and children. A study conducted in Egypt among pregnant women with
iron-deficiency anemia found that taking 100-mg lactoferrin oral sachets (MamyVital, Dulex Lab,
Cairo, Egypt) twice daily for 4 weeks increased blood levels of iron by 37%
compared to iron supplements alone (Darwish, J Matern Fetal
Neonatal Med 2019). The iron content of this lactoferrin supplement
was not described by the researchers, but information on the manufacturer's website
suggests that each 200-mg dose of MamyVital provides
about 31 mg of iron. A similar product available in the U.S. is IronSorb + Lactoferrin by Jarrow Formula, which provides 200 mg of lactoferrin and 18
mg of iron. (Note: This product has not been reviewed by ConsumerLab.com to
confirm its ingredients.)
A study in Kenya among 25 infants (average age 4 months),
most of whom were iron deficient, found that eating maize porridge fortified
with 1.5 mg of iron (as ferrous sulfate) and 1.4 grams of apolactoferrin (a form of lactoferrin with minimal
iron) increased iron absorption by 56% compared to eating the iron-fortified
meal without lactoferrin. However, eating a meal fortified with lactoferrin
as holo-lactoferrin (a form of lactoferrin that is saturated with
iron) increased iron levels only as effectively as eating the meal fortified
with iron as ferrous sulfate, suggesting no added benefit (Mikulic, J Nutr 2020). Holo-lactoferrin is not the
form of lactoferrin included in most lactoferrin supplements available in the
U.S. For more information about lactoferrin, particularly its effects on the
immune system, see our answer to the question: What is lactoferrin and will it
really strengthen my immune system?
Another form, carbonyl iron, may present a
reduced risk of harm in an accidental overdose. Carbonyl iron, consequently, is
the ingredient many children's supplements contain and may be preferred by
parents of small children. However, carbonyl iron requires adequate stomach
acid for absorption. Therefore, it should be taken with food and not used with
medications that reduce stomach acid.
Injectable iron also is available under the supervision of a health
professional.
Taking iron supplements with food may also help avoid
gastric upset, although it may also decrease iron absorption. Some experts
suggest taking iron with a vitamin C-rich food to boost iron absorption and
offset this effect. In fact, some iron supplements contain vitamin C as an
added ingredient to aid absorption, but some research suggests that it may not make a difference.
Constipation can be a side-effect of oral
iron supplementation, especially when taken in higher doses (Fei, Clinical Correlations 2015). Ferrous and
ferrous salts (ferrous sulfate, ferrous gluconate, ferrous fumarate and ferrous
glycinate sulfate) have been found to have similar incidence of constipation
when compared in a clinical study (Hallberg, Acta Med Scand Suppl
1966). However, heme iron polypeptides, carbonyl iron, iron
amino-acid chelates, and PIC may have a lower incidence of gastrointestinal
side-effects than ferrous or ferric salts (NIH Iron Fact Sheet 2016). Iron
protein succinylate has also been found to
have a slightly lower incidence of constipation and less gastric irritation.
Long term, it may result in somewhat greater improvement in iron measurements
in the body than ferrous sulfate (Liquori, Int J Pharmacol Ther Toxicol 1993).
Iron protein succinylate is the form found in Life
Extension Iron Protein Plus in this Review. Rarely, severe
constipation due to iron supplementation may interfere with the intestine's
ability to properly contract (to move waste through the body), leading to bowel
obstruction, as was reported in a 55-year-old women
one week after she began taking iron pills to treat iron deficiency
anemia. Increasing dietary fiber intake and/or using stool softeners
can help to prevent constipation when taking iron supplements (Parvataneni, Cureus 2020).
What to avoid when taking
Remember that many antacids can decrease iron absorption, and
the dose and duration of use of certain antacids may increase the risk of iron
deficiency. For example, taking 20 mg or more daily of a
proton pump inhibitor (PPI) drug such as omeprazole (Prilosec), esomeprazole
(Nexium) or lansoprazole (Prevacid) for more than one
year was associated with 3.6 times the risk of iron deficiency, while
"intermittent use" of PPIs during the same time period was associated
with a 50% increased risk of deficiency, compared to no use of PPIs, according
to an analysis of over 50,000 people in the United Kingdom (Tran-Duy, J Intern Med 2018).
Certain foods and beverages, including soy protein, coffee,
eggs, whole-grain cereals and breads, and spinach, can also reduce iron
absorption, as can tea (Gillooly, Br J Nutr 1983; Hurrell, Am J Clin Nutr 2010).
A small study in England showed that consuming about one cup of brewed black
tea with an iron containing meal reduced the amount of iron normally
absorbed by 37%. However, consuming tea one hour after the meal had no effect on
iron absorption (Fuzi, Am J Clin Nutr 2017). Green tea (one
large, 10 oz cup) was found to cause about an 80% reduction in iron absorption
from an iron-containing meal (including iron-enriched bread) as opposed to
consuming the meal with mineral water (Lazrak, J Nutr 2021).
Iron absorption also can be reduced by high doses of
other minerals, such as zinc, manganese, magnesium or copper. When consuming
high-dose mineral supplements, or one of the foods noted above, wait 2 hours to
take your iron supplement. Calcium is particularly prone to inhibiting iron
absorption: A study showed that taking a calcium supplement (300 mg or 600 mg
of calcium) at the same time as taking an iron supplement reduced iron
absorption by as much as 62%. Calcium similarly reduced iron absorption from
food (Cook, Am J Clin Nutr 1991).
This interaction is not likely to be a significant problem with lower doses of
calcium (under 200 mg) or for people who are not prone to iron deficiency. Be
aware that some multivitamins for women (who
are most at-risk for iron deficiency if they have not yet gone through
menopause) contain 500 mg or more of calcium.
Concerns and Cautions:
Although
iron supplements are safe and potentially helpful when taken in appropriate
amounts, excessive iron intake can be harmful:
·
The most common immediate side effect of iron supplements
is gastrointestinal distress including constipation, nausea,
and diarrhea. Nausea and stomach upset often occurs when a high-dose iron
supplement is taken on an empty stomach. This risk of nausea and
gastrointestinal upset may be reduced with certain forms of iron and/or by
taking iron with food. Certain forms of iron are also less likely to cause
constipation; increasing dietary fiber intake and using stool softeners may
also help (see Forms of Iron and Avoiding Stomach Upset).
·
Occasionally, use of iron pills can damage the protective lining
of the stomach, leading to stomach erosions and ulcers, and
gastrointestinal bleeding (known as iron-pill induced gastropathy),
which can result in a worsening of anemia. This may be more likely to occur in
older adults. The liquid form of oral iron (as well as intravenous iron) is
less likely to damage the lining of the stomach. Reported cases have included
two men (ages 72 and 81) and a woman (age 90) in Florida, all of whom were
taking tablets providing 325 mg of iron (as ferrous sulfate) one to two times
daily to treat iron-deficiency anemia. Their symptoms resolved after they were
switched to intravenous iron for their anemia and their stomach damage was
treated with medication (Comba, American College of Gastroenterology Annual Scientific Meeting 2019).
Gastritis and a non-bleeding stomach ulcer were also reported in a 46-year-old
woman taking iron pills for iron-deficiency anemia (Sunkara, Gastroenterology Res 2017).
·
Iron at greatly excessive doses taken continually can result in
toxicity, causing cirrhosis, coronary heart disease, congestive heart failure,
and other problems.
·
Other problems can occur with prolonged excessive intake of
iron. For example, while pregnant women are generally encouraged to take iron
supplements, supplementation beyond the recommended amount may increase
complications of pregnancy. Also, one study found that non-iron-deficient,
breast-fed infants do not benefit from iron supplements. These infants might
even experience an overall decrease in health if given iron supplementation.
·
Observational studies have found associations between mildly
excessive levels of stored iron in the body and heart disease, cancer
and type 2 diabetes. Higher levels of stored iron have also been
associated with a modestly higher risk of stroke, particularly
cardioembolic stroke (i.e., stroke due to clot or plaque debris coming from the
heart), possibly due to an excess of iron triggering clot formation (Gill, Stroke 2018). This
does not prove that excessive iron intake causes those diseases, but it does
suggest a connection. Interestingly, analysis of U.S. data found that,
among women, the risk of stroke actually decreased with intake
of iron (from the diet or supplements) up to 20 mg daily, which is similar to
the RDA for women up to age 50, although there was no further decrease with
higher iron intake. There was no association between dietary iron intake and
stroke risk in men (Xu, Int J Environ Health Res 2021). On
this basis, it appears prudent to suggest that people should be sure to attain
adequate amounts of iron from their diet but should generally not take iron
supplements unless blood tests have shown them to be iron deficient. Note that
non-vegetarian adult men and post-menopausal women are unlikely to lack
adequate iron. In fact, according to the CDC, 29% of men are at-risk for iron excess.
·
A study of postmenopausal women found the use of iron
supplements to be associated with a 3.9% increased risk of death over
a 22-year period. The risk increased as the dosage increased (particularly at
very high dosages of 50 mg to several hundred milligrams per day) (Mursu, Ach Int Med 2011). However, the study grouped
dosages of under 50 mg together, making it hard to determine the risk of lower
dosages of iron, such as those in many multivitamins.
·
Use of iron supplements before or during chemotherapy
for breast cancer has been associated with a with a 91% higher risk of
cancer recurrence (Ambrosone, J Clin
Oncol 2020).
·
Vitamin C may increase iron absorption, although it does not
seem to be necessary to take it with iron in order to boost hemoglobin and
ferritin levels. Consequently, people who take very high doses of vitamin C (a
gram or more daily) may be at increased risk of iron toxicity. Toxicity is of
particular concern for individuals with hemochromatosis, a genetic condition
affecting 1 out of 200 to 500 people. With hemochromatosis, excessive amounts
of iron build up in the body's tissues and organs.
·
High doses of ferrous iron (but not ferric
iron) or other minerals (calcium, magnesium, and zinc) from supplements may
decrease the absorption of carotenoids, such as beta-carotene, lycopene and astaxanthin, from foods
and/or supplements. This is likely due to a reaction between carotenoids and
the divalent ions of these minerals, making the carotenoids less bioavailable (Corte-Real, Food Chem 2016; Biehler, J Nutr 2011). It
is best to take carotenoid supplements at a different time of day than
a supplement or meal containing large amounts of a mineral.
Iron supplements also may reduce the absorption of certain drugs
such as levodopa, levothyroxine, penicillamine, quinolone antibiotics,
tetracycline antibiotics, and, possibly, ACE-inhibitors.
Conversely, some of these drugs may interfere with iron absorption. It is best
to take these medications at a different time of day than when taking an iron
supplement. This caution may also apply to the anti-seizure
medication carbamazepine, as suggested by a study that found that iron
supplementation may lower carbamazepine concentrations by as much as
approximately 30%, possibly by reducing bioavailability (Ahn,
Epilepsy Res 2019).
Remember, iron supplements are a leading cause of poisoning in children younger
than age 6. Just a few adult tablets can cause serious poisoning, so keep iron
products away from children's reach. To help reduce the number of such
poisonings, supplements containing 30 mg or more of iron (other than carbonyl
iron) can only be sold in child-resistant bottles or in single-dose packaging.
An excellent Fact Sheet about
iron supplementation is available from the government Office of Dietary
Supplements.
Information on this site
is provided for informational purposes only. It is not an endorsement of any
product nor is it meant to substitute for the advice provided by physicians or
other healthcare professionals. The information contained herein should not be
used for diagnosing or treating a health problem or disease. Consumers should
inform their healthcare providers of the dietary supplements they take.
Latest Clinical Research Updates for Iron Supplements
9/21/2021
Recommended doses for
correcting iron deficiency may be too high, according to recent guidelines. Get
the details in the ConsumerTips section of our Iron
Supplements Review. Also, see our Top Picks among iron supplements.
Don't Do This If You Need Iron
5/29/2021
If you're low in iron, be
aware that many foods dramatically reduce absorption of iron from your diet.
Teas can also have a major impact, as shown in a recent study. Get the details
in the What to Avoid section of our Iron
Supplements Review. Also see our Top Picks among iron supplements.
5/22/2021
There are downsides to
taking too much iron, but a recent analysis suggests that getting a basic
amount of iron may reduce stroke risk for women. Get the details in the Concerns and Cautions section of our Iron
Supplements Review.
Fibromyalgia Risk With Iron Deficiency
Anemia?
5/22/2021
A recent study suggests a
link between iron deficiency anemia and fibromyalgia, particularly in women.
Get the details in the What It Does section of our Iron
Supplements Review. Also see our Top Picks among iron supplements.
Lactoferrin for Iron Absorption?
11/18/2020
Can taking lactoferrin
with iron boost iron absorption? Learn what studies are showing in the Forms of Iron section
of our Iron Supplements review. Also, see our Top Picks for iron.
Related CL Answers (23)