How to Increase the Absorption of Iron From Foods
By Dr. Verena
Iron is an essential mineral your body needs to function properly.
Thus, it's vitally important to consume adequate amounts of it in your daily diet.
Interestingly, the foods you eat influence not only how much iron you consume, but also how well it is absorbed into your body (1).
Once it's absorbed by your body, it's used as a building block for hemoglobin, a protein found in red blood cells that helps shuttle oxygen around your body.
Iron is also a component of myoglobin, an oxygen storage protein found in your muscles. This oxygen is used when you use your muscles.
The recommended intake range is 7–18 mg per day for the general population and up to 27 grams for pregnant women (2).
Which Foods Contain It?
You may have heard that you can get iron from red meat, but there are many other foods that naturally contain iron.
In foods, iron is present in two forms: heme and non-heme.
Sources of Heme Iron
Heme iron is found in animal foods that contain hemoglobin, such as meat, fish and poultry.
Heme iron is the best form of iron, as up to 40 percent of it is readily absorbed by your body (3).
Good food sources of heme iron include:
- Fish such as halibut, haddock, perch, salmon or tuna
- Shellfish such as clams, oysters and mussels
Sources of Non-Heme Iron
Non-heme iron primarily comes from plant sources and is present in grains, vegetables and fortified foods.
This is the form added to foods enriched or fortified with iron, as well as many supplements.
In terms of its bioavailability, non-heme iron is absorbed much less efficiently than heme iron.
Good sources of non-heme iron include:
- Fortified cereals, rice, wheat and oats
- Dark green leafy vegetables like spinach and kale
- Dried fruits like raisins and apricots
- Beans like lentils and soybeans
Summary: Heme iron is found in animal foods, while non-heme iron comes from plant sources. The heme form is better absorbed by your body than the non-heme form.
Certain Populations May Be at Risk of Deficiency
A person who is iron deficient may have various symptoms, including fatigue, dizziness, headaches, sensitivity to cold and shortness of breath when doing simple tasks.
Children, adolescents and women of reproductive age, particularly during pregnancy, are most at risk of iron deficiency. This is because their intake doesn't meet their body's high demand for it (1).
Additionally, it's commonly thought that vegetarians and vegans are more prone to iron deficiency. But, interestingly, studies have shown that vegetarian and vegan diets contain just as much iron, if not more, than diets containing meat (10, 11, 12).
However, although vegetarians may consume as much iron as non-vegetarians, a review found that they are still at greater risk of deficiency (6).
This is because they consume mainly non-heme iron, which is not absorbed as well as the heme form in animal products.
It's generally recommended that vegetarians multiply their recommended iron intake by 1.8 times to compensate for the reduced absorption (12).
Summary: Iron deficiency is very common. Those who are most at risk include children, adolescents, women of reproductive age, pregnant women, vegetarians and vegans
Foods That Help You Absorb More Iron
While not all dietary iron is absorbed equally, some foods can enhance your body's ability to absorb it.
Foods Rich in Vitamin C
Vitamin C has been shown to enhance iron absorption. It captures non-heme iron and stores it in a form that's more easily absorbed by your body (3).
Foods high in vitamin C include citrus fruits, dark green leafy vegetables, bell peppers, melons and strawberries.
In one study, taking 100 mg of vitamin C with a meal increased iron absorption by 67 percent (13).
Hence, drinking citrus juice or eating other foods rich in vitamin C while you're eating high-iron foods can increase your body's absorption.
In vegetarian and vegan diets, iron absorption may be optimized by including vitamin C-containing vegetables during meals (1).
Foods With Vitamin A and Beta-Carotene
Vitamin A plays a critical role in maintaining healthy vision, bone growth and your immune system.
Beta-carotene is a red-orange pigment found in plants and fruits. It can be turned into vitamin A in your body.
Good food sources of beta-carotene and vitamin A include carrots, sweet potatoes, spinach, kale, squash, red peppers, cantaloupe, apricots, oranges and peaches.
One study of 100 people given cereal-based meals found that the presence of vitamin A increased iron absorption by up to 200 percent for rice, 80 percent for wheat and 140 percent for corn (14).
In the same study, adding beta-carotene to the meals increased absorption more than 300 percent for rice and 180 percent for wheat and corn (14).
Meat, Fish and Poultry
Meat, fish and poultry not only provide well-absorbed heme iron, they can also stimulate absorption of the non-heme form.
Research has also shown that adding 75 grams of meat to a meal increased the absorption of non-heme iron by about 2.5 times, compared to a meal without it (4).
Based on study findings, it was estimated that 1 gram of meat, fish or poultry provided an enhancing effect similar to that of 1 mg of vitamin C (4).
Summary: You can enhance the absorption of iron from meals by eating foods high in vitamin C, vitamin A or beta-carotone. Eating meat, fish or poultry with other foods can also help.
Foods That May Hinder Iron Absorption
Just as some foods can improve iron absorption, others can hinder it.
Foods Containing Phytate
In one study, as little as 2 mg of phytate in foods inhibited iron absorption by 18 percent when added to wheat rolls. And when 250 mg of phytate was eaten, up to 82 percent was not absorbed (4).
Nonetheless, the negative effect of phytate can be counteracted by consuming foods that enhance non-heme iron absorption, such as vitamin C or meat.
Calcium is an essential mineral for bone health.
This is worrisome, as increased calcium intake is commonly recommended for children and women, the same populations that are at risk of iron deficiency.
However, most studies were short-term and conducted in single meals. A thorough review of long-term studies found that calcium and milk products did not have any adverse effects on absorption (16).
To maximize absorption, calcium-rich foods should not be eaten with meals that provide most of your dietary iron.
In the case of supplements, calcium and iron supplements should be taken at different times of the day, if possible.
Foods Containing Polyphenols
Polyphenols are found in various amounts in plant foods and beverages, including vegetables, fruits, some cereals and legumes, tea, coffee and wine.
Coffee and tea, both of which are widely consumed around meals, have a high content of polyphenols, and they have been shown to inhibit the absorption of non-heme iron (13).
In one review, drinking a cup of black tea with a meal reduced iron absorption by 60–70 percent, regardless whether the tea was weak, normal or strong.
However, when participants drank tea between meals, the reduction in absorption was only about 20 percent (4).
To counteract the negative effect of polyphenols, be sure to leave a couple of hours between your iron-rich meal and your afternoon tea or coffee.
Summary: Foods containing phytates, calcium and polyphenols can significantly reduce iron absorption.
Health Risks of Excessive Iron
Iron toxicity from food sources is rare. Once it is consumed, your body has its own balancing system to make certain that it gets just enough.
Nevertheless, one report showed that deadly overdoses were possible with excessive intakes of iron supplements (18).
Excessive iron levels can also occur in some people with a condition called hemochromatosis. This is usually caused by a gene that enhances absorption (19).
Other causes of iron overload include repeated blood transfusions, massive doses from the diet and rare metabolic disorders.
Additionally, consuming too much iron over time may cause large deposits of it to form in the liver and other tissues.
You should probably never take an iron supplement unless when recommended to you by a health professional.
Summary: Consuming too much iron can have health risks. Because of this, supplements are not recommended for most people.
Tips to Get Enough Iron
The tips below can help you maximize your dietary iron intake:
- Eat lean red meat: This is the best source of easily absorbed heme iron. Eating it several times per week can help if you are deficient.
- Eat chicken and fish: These are also good sources of heme iron. Eat a variety of them.
- Consume vitamin C-rich foods: Eat vitamin C-rich foods during meals to increase the absorption of non-heme iron. For example, some lemon juice drizzled over leafy greens will increase the amount you absorb.
- Avoid coffee, tea or milk near meals: Avoid these during meals that contain iron-rich foods. Have your coffee or tea between meals instead.
- Choose foods rich in non-heme iron: If you don't eat meat and fish, include plenty of iron-rich plant foods in your diet.
Summary: To maximize your iron intake, try to include meat, fish, poultry, beans and lentils in your diet, as well as vitamin C-rich foods during your meals. Also, spread out your tea, coffee and dairy intakes between meals.
The Bottom Line
Iron is a vital mineral that's essential for the function of your body. Two types of it are found in food—heme and non-heme.
Meat, fish and poultry contain the heme form, which is easily absorbed by your body.
Non-heme iron is mainly found in plant foods, but this form is harder for your body to absorb. You can improve your body's absorption by eating foods containing vitamin C, vitamin A, meat, fish and poultry during your meals.
On the other hand, foods containing phytates (cereals and grains), calcium (milk and dairy) and polyphenols (tea and coffee) can hinder iron absorption.
By carefully selecting the foods you eat and knowing how certain foods can enhance or inhibit absorption, you can make sure you're getting the iron you need.
Reposted with permission from our media associate Authority Nutrition.
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Hanako, a female Asian elephant, lived in a tiny concrete enclosure at Japan's Inokashira Park Zoo for more than 60 years, often in chains, with no stimulation. In the wild, elephants live in herds, with close family ties. Hanako was solitary for the last decade of her life.
Hanako, an Asian elephant kept at Japan's Inokashira Park Zoo; and Kiska, an orca that lives at Marineland Canada. One image depicts Kiska's damaged teeth. Elephants in Japan (left image), Ontario Captive Animal Watch (right image), CC BY-ND
Affecting Health and Altering Behavior<p>It is easy to observe the overall health and psychological consequences of life in captivity for these animals. Many captive elephants suffer from arthritis, obesity or skin problems. Both <a href="https://doi.org/10.11609/JoTT.o2620.1826-36" target="_blank">elephants</a> and orcas often have severe dental problems. Captive orcas are plagued by <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank">pneumonia, kidney disease, gastrointestinal illnesses and infections</a>.</p><p>Many animals <a href="https://doi.org/10.1016/j.neubiorev.2017.09.010" target="_blank">try to cope</a> with captivity by adopting abnormal behaviors. Some develop "<a href="https://doi.org/10.1016/j.applanim.2017.05.003" target="_blank" rel="noopener noreferrer">stereotypies</a>," which are repetitive, purposeless habits such as constantly bobbing their heads, swaying incessantly or chewing on the bars of their cages. Others, especially big cats, pace their enclosures. Elephants rub or break their tusks.</p>
Changing Brain Structure<p>Neuroscientific research indicates that living in an impoverished, stressful captive environment <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank" rel="noopener noreferrer">physically damages the brain</a>. These changes have been documented in many <a href="https://doi.org/10.1002/cne.903270108" target="_blank" rel="noopener noreferrer">species</a>, including rodents, rabbits, cats and <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">humans</a>.</p><p>Although researchers have directly studied some animal brains, most of what we know comes from observing animal behavior, analyzing stress hormone levels in the blood and applying knowledge gained from a half-century of neuroscience research. Laboratory research also suggests that mammals in a zoo or aquarium have compromised brain function.</p>
This illustration shows differences in the brain's cerebral cortex in animals held in impoverished (captive) and enriched (natural) environments. Impoverishment results in thinning of the cortex, a decreased blood supply, less support for neurons and decreased connectivity among neurons. Arnold B. Scheibel, CC BY-ND<p>Subsisting in confined, barren quarters that lack intellectual stimulation or appropriate social contact seems to <a href="https://doi.org/10.1590/S0001-37652001000200006" target="_blank" rel="noopener noreferrer">thin the cerebral cortex</a> – the part of the brain involved in voluntary movement and higher cognitive function, including memory, planning and decision-making.</p><p>There are other consequences. Capillaries shrink, depriving the brain of the oxygen-rich blood it needs to survive. Neurons become smaller, and their dendrites – the branches that form connections with other neurons – become less complex, impairing communication within the brain. As a result, the cortical neurons in captive animals <a href="https://doi.org/10.1002/cne.901230110" target="_blank">process information less efficiently</a> than those living in <a href="https://doi.org/10.1002/dev.420020208" target="_blank">enriched, more natural environments</a>.</p>
An actual cortical neuron in a wild African elephant living in its natural habitat compared with a hypothesized cortical neuron from a captive elephant. Bob Jacobs, CC BY-ND<p>Brain health is also affected by living in small quarters that <a href="https://doi.org/10.3233/BPL-160040" target="_blank">don't allow for needed exercise</a>. Physical activity increases the flow of blood to the brain, which requires large amounts of oxygen. Exercise increases the production of new connections and <a href="http://dx.doi.org/10.1126/science.aaw2622" target="_blank">enhances cognitive abilities</a>.</p><p>In their native habits these animals must move to survive, covering great distances to forage or find a mate. Elephants typically travel anywhere from <a href="https://www.elephantsforafrica.org/elephant-facts/#:%7E:text=How%20far%20do%20elephants%20walk,km%20on%20a%20daily%20basis." target="_blank">15 to 120 miles per day</a>. In a zoo, they average <a href="https://doi.org/10.1371/journal.pone.0150331" target="_blank" rel="noopener noreferrer">three miles daily</a>, often walking back and forth in small enclosures. One free orca studied in Canada swam <a href="https://doi.org/10.1007/s00300-010-0958-x" target="_blank" rel="noopener noreferrer">up to 156 miles a day</a>; meanwhile, an average orca tank is about 10,000 times smaller than its <a href="https://www.cascadiaresearch.org/projects/killer-whales/using-dtags-study-acoustics-and-behavior-southern" target="_blank" rel="noopener noreferrer">natural home range</a>.</p>
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Damaged Wiring<p>Captivity can damage the brain's complex circuitry, including the basal ganglia. This group of neurons communicates with the cerebral cortex along two networks: a direct pathway that enhances movement and behavior, and an indirect pathway that inhibits them.</p><p>The repetitive, <a href="http://dx.doi.org/10.1016/j.bbr.2014.05.057" target="_blank">stereotypic behaviors</a> that many animals adopt in captivity are caused by an imbalance of two neurotransmitters, dopamine and <a href="https://doi.org/10.1016/j.neubiorev.2010.02.004" target="_blank" rel="noopener noreferrer">serotonin</a>. This impairs the indirect pathway's ability to modulate movement, a condition documented in species from chickens, cows, sheep and horses to primates and big cats.</p>
The cerebral cortex, hippocampus and amygdala are physically altered by captivity, along with brain circuitry that involves the basal ganglia. Bob Jacobs, CC BY-ND<p>Evolution has constructed animal brains to be exquisitely responsive to their environment. Those reactions can affect neural function by <a href="https://www.penguinrandomhouse.com/books/311787/behave-by-robert-m-sapolsky/" target="_blank">turning different genes on or off</a>. Living in inappropriate or abusive circumstance alters biochemical processes: It disrupts the synthesis of proteins that build connections between brain cells and the neurotransmitters that facilitate communication among them.</p><p>There is strong evidence that <a href="https://doi.org/10.1523/JNEUROSCI.0577-11.2011" target="_blank">enrichment</a>, social contact and appropriate space in more natural habitats are <a href="https://doi.org/10.1111/j.1748-1090.2003.tb02071.x" target="_blank" rel="noopener noreferrer">necessary</a> for long-lived animals with large brains such as <a href="https://doi.org/10.1371/journal.pone.0152490" target="_blank" rel="noopener noreferrer">elephants</a> and <a href="https://doi.org/10.1080/13880292.2017.1309858" target="_blank" rel="noopener noreferrer">cetaceans</a>. Better conditions <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5543669/" target="_blank" rel="noopener noreferrer">reduce disturbing sterotypical behaviors</a>, improve connections in the brain, and <a href="https://doi.org/10.1038/cdd.2009.193" target="_blank" rel="noopener noreferrer">trigger neurochemical changes</a> that enhance learning and memory.</p>