Iron is essential for many vital processes. Iron deficiency can cause anemia and many other health problems. Low iron has been linked with various diseases and disorders. Read this post to learn about the negative health effects of iron deficiency and to find out what diseases make iron deficiency more likely.
Conditions Associated with Iron Deficiency
Some of the conditions below are caused by a lack of iron, others may cause a lack of iron, but most have only an association with iron deficiency. This means that there isn’t enough evidence to claim that iron deficiency causes them or that they cause iron deficiency.
Some are also complex conditions that have multiple causes, and iron deficiency may only play a minor part in their development.
Remember, just because your iron may be low, that doesn’t mean you have any of the conditions listed below.
If your iron is low, work with your doctor to find out what’s the cause and to treat any underlying health issues!
Cognitive Function and Development
In terms of brain development and brain health, iron is critical for [1, 2, 3, 4]:
- brain and neurological development
- normal functioning of the brain
- neurotransmitter production (dopamine and noradrenaline)
- myelination of nerve cells
There is research that suggests that iron deficiency contributes to psychiatric and developmental disorders.
1) Attention Deficit Hyperactivity Disorder
Lower iron and ferritin levels have been associated with increased hyperactivity in children with ADHD [5, 6].
Blood ferritin levels were low (<30 ng/mL) in 84% of the children with ADHD as compared to 18% of healthy children [7, 8, 9].
In addition, among people with ADHD, low blood ferritin levels were associated with the severity of ADHD symptoms and worse cognitive function [10, 11].
There are a couple of studies that found a link between iron deficiency anemia and an increased risk of ADHD [12, 13].
Research suggests that low brain iron stores may contribute to ADHD symptoms because low iron levels in the brain can alter the activity of dopamine, a neurotransmitter involved in movement, cognitive functions, and attention [10].
Several studies found that iron supplementation improved ADHD symptoms in children with low blood ferritin levels [14, 15, 8].
2) Autism
Iron deficiency and anemia are prevalent among autistic children [16, 17, 12].
This is likely linked with selective or picky eating and sensory sensitivity that predisposes autistic people to restricted food intakes [18].
Researchers think that iron deficiency may contribute to learning and behavioral impairments observed in children with autism spectrum disorder (ASD) [19].
However, it’s important to stress that not all autistic children have low iron [20].
3) Mental Retardation and Delayed Development
Studies suggest that mental retardation and delayed development are more prevalent in children who have iron deficiency [21, 22, 12].
Iron deficiency impairs cognitive, social, and behavioral development [23, 24].
In a study of over 5k children, those with iron deficiency anemia were more than twice as likely to score below average on standardized tests than children with normal iron status [25].
4) Anxiety
Studies suggest that iron deficiency may impair dopaminergic neurotransmission and depress dopaminergic activity. An association between iron deficiency anemia and anxiety has been found in both men and women [12].
Weaning rats fed an iron-deficient diet showed decreased physical activity and increased anxiety-like behavior with a reduction of brain dopamine receptors [26].
5) Bipolar Disorder
Iron deficiency can cause mood swings, a key factor in the disease progression of bipolar disorder [22, 27, 28, 29].
A study suggests that bipolar disorder may be more prevalent among female children and adolescents with iron deficiency anemia [30].
6) Tic Disorder
Research has found a link between iron deficiency anemia in women and tic disorder [31].
Ferritin and blood iron levels were markedly lower in a study of children and adults with Tourette’s syndrome [32].
Women’s Health
Women of reproductive age are at particular risk of iron deficiency, because they can lose significant amounts of iron with menstrual blood [33].
Data from the National Health and Nutrition Examination Survey indicated that 12 – 16% of nonpregnant women aged 16 – 49 years have iron deficiency, and 2 – 4% have iron-deficiency anemia [34].
In fact, heavy menstrual bleeding is the most common cause of iron deficiency anemia in the developed world [35].
Other factors that increase the risk of iron deficiency in women include [33, 36, 37]:
- the use of an intrauterine device (IUD)
- a vegetarian diet
- accelerated growth during the teenage years
- dieting
- intensive exercise
Research suggests that women are at greater risk of experiencing fatigue and exhaustion and are 3 times more likely than men to feel fatigued [38].
7) Premenstrual Syndrome (PMS)
Low intake of iron has been associated with a higher risk of premenstrual syndrome [39].
Studies have found that PMS symptoms are more severe in anemic women compared to non-anemic women [40].
In one study, taking dietary and iron supplements for 2 months reduced PMS symptoms considerably in all women having anemia [40].
In another study, eating a diet that provided about 22 mg of iron every day for 10 years was linked to a 33% decrease in risks of developing premenstrual syndrome [39].
8) Pregnancy Complications
Research suggests that anemia occurs in 35 – 75% of pregnancies in developing countries, and in 18% of pregnancies in developed countries [41].
Iron requirements are increased during pregnancy because the mother’s blood volume expands, and the developing fetus and placenta need iron to grow [41].
Scientists have found a link between iron deficiency and higher maternal and fetal risk of death, premature delivery, and lower birth weight [42, 43, 44].
In fact, some studies suggest that iron deficiency anemia doubles the risk of preterm delivery and triples the risk of low birth weight [45, 46, 47].
Severe maternal anemia has been associated with growth delays and impaired neurological and mental development in newborns [48, 49, 50].
Furthermore, iron deficiency after delivery has been associated with an increased risk of postpartum depression, increased prevalence of infections, fatigue, and exhaustion, and lower quality and quantity of breast milk produced [51, 52, 53, 54].
Immune Function
Iron plays an essential role in the normal development of the immune system and resistance to infections [55, 56].
- immune cell production
- cytokine production
- immune response
- the generation of reactive oxygen species required for killing pathogens
9) Compromised Immune Function
Scientists have found that iron deficiency may reduce the function of lymphoid organs (tissues that produce white blood cells (lymphocytes)) and immune cells, specifically it may be associated with:
- thymus degeneration, resulting in a decrease of T lymphocytes [59].
- reduced neutrophil activity against bacteria. Myeloperoxidase, an enzyme in neutrophils required for killing bacteria, needs iron to function [60]. Neutrophil function can be restored to normal with iron supplementation [61, 56, 62].
- reduced cytokine production, including IFN-gamma, TNF-alpha, IL-6, and IL-8
- reduced macrophage functions because iron accumulation within macrophages allows them to generate reactive oxygen species needed to combat infectious agents and cancer cells [63]
- Th2 dominance and lowered Th1 immune responses, which lowers the ability to fight off viral and bacterial infections [64]. Also, functions and growth of Th1 cells have been shown to be more sensitive to iron removal than Th2 cells in a cell-based study [65].
Antibody concentrations, production, responses to antigens, and complement levels (also called humoral immunity) seem to be less affected by iron deficiency [66].
However, while iron deficiency hampers the recovery and morbidity of some infections, it seems to help with other infections [67]. That’s because some microbes actually need iron to thrive.
10) Skin Problems and Poor Wound Healing
Iron is essential for healthy skin, hair, and nails. Iron is required for collagen production.
Signs of iron deficiency include pale and itchy skin, skin infections (impetigo, candidiasis), fragile nails, and dry and brittle hair [68].
Severe deficiency results in decreased collagen production, and poor wound healing [69].
Studies suggest that iron may also play a role in skin changes seen in sunburn, porphyria cutanea tarda, inflammation, and skin cancer [70, 71, 72, 73].
Chronic Infections
11) Helicobacter pylori Infection
H.pylori infection is associated with iron-deficiency anemia, particularly in children. A study suggests that iron deficiency is 40% more prevalent in children infected with H.pylori than in healthy children [74].
Bleeding in the gut and bacterial competition for iron are partially responsible for iron deficiency in those with the infection [75].
12) Parasitic Infection
People with intestinal parasitic infections commonly experience iron deficiency, mainly from chronic blood loss [76].
Autoimmune Disease
Chronic inflammation in autoimmunity can cause functional iron deficiency. This type of anemia is called Anemia of Chronic Inflammation (or anemia of chronic disease) and it’s one of the most common types of anemia [77].
What happens is that inflammatory cytokines move iron from the blood into the immune cells, which lowers the amount of iron available for the microbes but also decreases the amount of iron that can be used for important processes in the body such as the production of blood cells.
Chronic inflammation also reduces iron absorption in the gut [78].
Variants in the iron transporter NRAMP1 (encoded by the SLC11A1 gene) have been associated with several autoimmune disorders including rheumatoid arthritis, diabetes and multiple sclerosis [79, 80, 81].
Also, researchers found that iron can increase the production of several autoantigens initiating the process of autoimmunity [82].
Therefore, iron deficiency has been associated with several autoimmune diseases, but iron deficiency is usually the effect rather than the cause.
However, keep in mind that not all autoimmune patients are anemic.
13) Rheumatoid Arthritis
Studies suggest that iron deficiency may be found in up to 30 – 60% of patients with rheumatoid arthritis [83, 84], while anemia may occur in 16 – 65% [85, 86].
The severity of the anemia seems to be associated with the activity of the disease [84].
Some studies suggest that iron supplementation may potentially decrease disease activity and joint tenderness [87, 88].
However, iron therapy in rheumatoid arthritis patients without iron deficiency may worsen joint inflammation, pain, and dysfunction [89].
14) Lupus
Iron deficiency is common in patients with systemic lupus erythematosus (SLE) due to heavy menstrual bleeding and increased gut blood loss, caused by the use of drugs such as aspirin and anticoagulants [90, 91].
Researchers have found that anemia of chronic disease frequently accompanies lupus flare-ups and may be a useful parameter of disease activity [92].
15) Inflammatory Bowel Disease (IBD)
Anemia is one of the most common manifestations of inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis [93, 94].
Both iron deficiency and anemia of chronic disease contribute to the development of anemia in IBD [95, 96].
Studies suggest that iron deficiency occurs in about 60 – 80% of patients with IBD [97].
Iron deficiency anemia in IBD is due to chronic blood loss, poor dietary intake of iron, and reduced iron absorption due to gut inflammation [93].
16) Celiac Disease
Iron deficiency is often found in people with celiac disease [98, 99].
Iron deficiency anemia is one of the main/presenting clinical features of celiac disease and may even be the only symptom in some [100, 101, 102].
Iron deficiency anemia was reported in up to 46% of people with celiac disease, occurring more often in adults than children [103].
Low iron is most often due to increased iron loss due to intestinal bleeding and decreased iron absorption in the gut [104, 98].
17) Autoimmune Gastritis
Autoimmune gastritis (inflammation of the stomach) is classically associated with pernicious anemia (anemia due to low vitamin B12) in adults, but recent studies have reported its association with iron-deficiency anemia in both adults and children [105].
In one study, autoimmune gastritis was present in 27 – 52% of patients with iron-deficiency anemia [106].
Decreased or absent gastric acid production due to gastritis (stomach inflammation) decreases the absorption of iron taken by mouth, and thus leads to iron-deficiency [105, 107].
Metabolic and Cardiovascular Health
18) Obesity
An inverse correlation between body mass and iron status has been reported in multiple observational studies in children and adults [108, 109].
This is likely due to chronic inflammation that accompanies obesity.
Scientists think that inflammation in obesity increases hepcidin, which then lowers iron absorption [110].
19) Thyroid Function
A deficiency of iron may have an adverse effect on thyroid function [111].
Iron deficiency decreases thyroid peroxidase function, an enzyme important in the production of thyroid hormones, thereby leading to hypothyroidism (underactive thyroid) [112].
Studies found a decrease in blood T3 and T4 levels and an increase in TSH levels in people with iron deficiency [113, 111].
Researchers found that providing iron along with iodine in those with impaired thyroid function resulted in greater improvements compared to iodine alone [114, 112].
20) Body Temperature
Those with iron-deficiency may have a decreased ability to maintain body temperature in response to cold [115].
In both experimental animals and humans, those with iron deficiency had reduced body temperature despite increased oxygen consumption and sympathetic activity [116, 117].
21) Heart Failure
Studies have found a link between iron deficiency and heart disease [118, 119]. In fact, according to research, iron deficiency is found in up to 20% of people with heart failure [120, 121].
In those with heart failure, iron deficiency has been associated with reduced exercise capacity, impaired quality of life, and increased risk of hospitalization [122, 120].
Researchers found that chronic iron deficiency can increase the size and weight of the heart [123, 124].
They also found that intravenous iron supplementation helps improve symptoms, quality of life, and reduces the need for hospital admissions among heart failure patients [125, 126].
The European Society of Cardiology Guidelines for heart failure recommends an evaluation of iron status in all patients with suspected heart failure [127].
However, keep in mind that increased iron stores have also been associated with an increased risk of heart diseases, especially in men and menopausal women. Iron buildup in the heart can also result in heart failure and produce irregular heart rhythms [128, 122].
22) Stroke
Studies have shown an association between stroke caused by blood clotting (ischemic stroke) and iron deficiency anemia [129, 130, 131].
Previously healthy children who had a stroke were 10 times more likely to have iron deficiency anemia than healthy children without a stroke [132].
Iron deficiency is associated with abnormal platelet levels and platelet dysfunction, which can increase the risks of stroke [133, 134, 135].
Thrombocytosis (high platelet count) due to iron deficiency anemia is a rare but recognized cause of stroke [136].
Other Negative Effects of Iron Deficiency
23) Pica
Iron deficiency anemia has been associated with pica, a condition where people develop unusual cravings for non-food items like ice and dirt [137].
24) Restless Leg Syndrome
Restless legs syndrome (RLS), also called Willis-Ekbom disease, is characterized by an urge to move the legs and transient relief with movement.
The symptoms occur at rest, are worst at night, and often interfere with sleep [138].
Scientists discovered that restless leg syndrome occurs four to five times more frequently in people with low blood and brain iron levels [139, 140, 141, 142].
Studies have shown that decreased blood ferritin levels were linked with increased severity of RLS symptoms [143, 144, 145].
Some scientists think that iron deficiency may be involved in disease development, possibly by affecting the production of the neurotransmitter dopamine [146].
The treatment of restless leg syndrome often includes iron therapy and the use of drugs like dopamine agonists [138].
Research has shown that iron supplements may also improve sleep, depression, fatigue, and quality of life in people with this syndrome who were initially iron deficient [147, 140, 148].
25) Physical Performance
Iron deficiency can affect physical performance by:
- lowering tissue cytochrome c and muscle myoglobin to about 50% of the normal values [149, 150, 151]
- decreasing oxygen uptake and use by muscles [152, 153, 154, 155]
- reducing oxygen supply to the heart and muscles, resulting in fatigue and decreased exercise performance [152, 156]
Work performance in anemic individuals can be improved with iron supplementation.
Studies have found that the increase in physical performance was about 4% higher in anemic men and about 12% higher in anemic women after supplementing with iron [157, 158].
Iron deficiency anemia is found in 2% of male athletes and in 2.5% of female athletes because heavy athletic training increases iron need.
Some types of athletes also often have a significant decrease in red blood cell number, hemoglobin, and ferritin levels [159].
26) Fatigue
Iron deficiency increases fatigue and decreases the quality of life in women [160].
Studies have found that iron deficiency is linked with fatigue in women even when they don’t have anemia [161, 162].
In one study, iron supplementation for 12 weeks decreased fatigue by almost 50% in menstruating iron-deficient women [163].
27) Fibromyalgia
Low blood ferritin has been associated with a 6.5 fold higher risk for fibromyalgia. This could be because iron is required for the production of serotonin, dopamine, and norepinephrine, which were found to be low in the cerebrospinal fluid of those with fibromyalgia [164].
28) Lung Disease
Iron deficiency is more common in people who have chronic obstructive pulmonary disease (COPD) [165].
Studies found that iron deficiency was associated with [165, 166, 167, 168]:
- worsening of COPD symptoms
- decreased exercise intolerance
- poor clinical outcome for COPD
- high blood pressure in the lungs without known causes (idiopathic pulmonary arterial hypertension)
Research suggests that treating iron deficiency and anemia in COPD patients may reduce shortness of breath, and may improve blood pressure in the lungs [169, 170].
29) Blood Pressure Medications (ACE inhibitor)-induced Cough
A dry cough is a common side effect of blood pressure-lowering drugs that are angiotensin-converting enzyme (ACE) inhibitors, such as Capoten and Vasotec.
An ACE inhibitor-induced cough may be associated with excessive production of dangerous nitrogen molecules in bronchial cells caused by iron deficiency.
Iron deficiency impairs the protective mechanisms of airway lining [171].
Researchers found that iron supplementation successfully decreases ACE inhibitor-induced cough [172].
30) Cystic Fibrosis
32% of pediatric and 60% of adult cystic fibrosis patients are deficient in iron, and iron deficiency has been associated with the severity of the disease [173].
31) Hair Loss
Hair follicle cells are sensitive to decreased iron, thus resulting in decreased hair growth in the presence of iron deficiency [174].
Studies report that 72% of women with hair loss had lower blood ferritin levels [175, 176].
Other studies have shown that iron supplementation can help reduce hair loss [177].
In one study, 18 women with hair loss experienced 100% hair regrowth after iron therapy. The hair loss recurred, however, when iron therapy was discontinued [174].
However, other studies showed no association between iron deficiency and female hair loss [178].
32) Chronic Kidney Disease (CKD)
Those with chronic kidney diseases often exhibit significant iron loss from chronic bleeding compared to individuals with normal kidney function. These effects are exacerbated with hemodialysis [179].
33) Lead Poisoning
Iron deficiency and lead poisoning are common among children in many parts of the world, especially children between the ages of 1 and 2 years [180, 181, 182].
Studies have found that children with iron deficiency are more likely to have elevated blood lead levels [183, 184, 185].
In fact, iron deficiency likely increases lead absorption, thus enhancing the toxic effects of lead [186, 187, 188].
Both lead poisoning and iron deficiency adversely affect red blood cell production (erythropoiesis) [189, 190].
An adequate intake of dietary iron is strongly recommended in order to lower blood lead levels and prevent the toxic effects of lead exposure [191, 192].
However, some studies suggest that therapeutic iron may actually interfere with lead excretion and may elevate lead levels [193, 194].
