Iron deficiency is the most common nutritional problem in the world, affecting at least 2.5 billion people. In developing countries, as many as 40% of young children and 50% of pregnant women are deficient. Iron is a prevalent mineral, making up 5% of the earth’s crust, but a combination of inefficiency in absorption, poor iron in certain staple grain foods, and medical conditions make low iron levels a frequent occurrence among humans. Even in first world countries, iron is the most common nutrient deficiency.
Low iron intake and accelerated iron loss (generally through bleeding or breastfeeding) are the main causes of iron deficiency. Therefore pregnant women, breastfeeding women, women with heavy periods, children and other folks who are picky eaters, vegetarians and vegans, and anyone with digestion issues causing reduced absorption (such as celiac disease or post gastric bypass) or increased bleeding (such as cancer, ulcers, gastritis, or parasites) are at higher risk for iron deficiency. High intake of calcium (for example in kids who drink a ton of milk) can interfere with iron absorption as well, along with commonly used medications such as antacids and proton-pump inhibitors for gastroesophageal reflux disease.
While we are used to thinking of low iron levels as causing anemia due to red blood cells’ requirement for iron as a part of hemoglobin, iron is also desperately needed for the nerves and brain. Severe iron deficiency in young children can cause irreversible damage to cognition and result in lower IQ and developmental delays, particularly during a critical period of human development in utero and up to 16 months of age.
Even in adults the first symptoms of iron deficiency are often neurologic, as those affected will frequently complain of fatigue, brain fog, and also restless legs causing insomnia. Pica, the odd behavioral compulsion to eat nonnutritive foods such as dirt or clay, is extremely common in areas of the world where iron deficiency is prevalent. In the developed world, pica is rare but still occurs in children, pregnant women, and among other groups at higher risk for iron deficiency including those who have had gastric bypass. Non-neurologic symptoms of iron deficiency include pallor, generalized weakness, and higher than usual heart rate along with shortness of breath, particularly with exertion.
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