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In 2001 U.S. researchers studied a group of 5398 children who were attending school, searching for possible links between academic success and nutrition. Although important micronutrients such as Vitamin B12 are often implicated in these kinds of studies,
The results of a 2001 study on a group 5,000 US elementary school students were somewhat alarming: lower math scores correlated strongly with iron deficiency (IDA). In fact, researchers calculated that children with an iron deficiency “had greater than twice the risk of scoring below average in math than did children with normal iron status.” Although
Appreciating the impact of iron levels on cognition and other biological processes is important because IDA is the most common nutritional deficiency in the U.S. Aside from cognitive impairments and behavioral disturbances among children, the Center for Disease Control and Prevention also cautions that IDA has a marked impact on expecting mothers, increasing the risk “for preterm delivery and a low-birthweight baby.”
Why is iron important?
Understanding the biological role of iron will help make sense of these risks. From an early age we all learn to appreciate the importance of breathing in oxygen. Without oxygen our bodily functions cease. This is because oxygen is required for burning fuel--either in the form of glucose or fatty acids. When we eat, we’re taking in fuel. When we breathe, we’re inhaling the spark to burn that fuel. For the match to catch fire in all the different parts of the body, however, the body needs a transport mechanism (imagine fire spreading quickly across a slick of oil). This is what iron does for the body. Embedded in compounds known as hemoglobin, iron helps transport oxygen from the blood in the lungs to tissues elsewhere in the body. As myoglobin, iron also receives and stores oxygen in muscle cells to be used for energy there. Finally, a smaller percentage of iron “is a component of certain proteins, essential for respiration and energy metabolism, and as a component of enzymes involved in the synthesis of collagen and some neurotransmitters” (UCSF).
Unlike Vitamin B12 and omega 3 fatty acids, which must be consistently obtained from exogenous sources, the body does a decent job of circulating and sustaining its own iron stores. But a few groups require higher amounts of iron due to unique circumstances. The rapid biological and cognitive development of children (particularly in pre-adolescent years) requires higher iron intake. For example, the NIH fact sheet on iron states that “breast milk contains highly bioavailable iron but in amounts that are not sufficient to meet the needs of infants older than 4 to 6 months.” Blood donors, pregnant women, women who recently gave birth, menstruating women, and menopausal women also experience significantly higher demands of exogenous iron. Despite the fact that women tend to lose iron more than men, they actually store less on average (300 mg compared to the adult male’s 1000 mg, according to the UCSF Medical Center).
When iron demand outstrips supply, individuals fall into a state known as anemia, exhibiting symptoms such as “gastrointestinal disturbances and impaired cognitive function, immune function, exercise or work performance, and body temperature regulation. In infants and children, IDA can result in psychomotor and cognitive abnormalities … .” Chronic shortages of iron is particularly serious among children, with some research showing it may have long term effects, extending through adulthood. (NIH)
Sources of iron
A good source of iron will be highly “bioavailable”, which means it’s readily absorbed and utilized by the body. This is important because many nutrition labels may show high amounts of iron, but that particular source may not be absorbed.
Fortified foods (low bioavailability): In the U.S., one of the most common sources of iron (up to 25%) is cereal and other prepackaged items. In order to meet FDA recommendations, most grocery store cereals “are fortified with low-cost elemental iron powders”. However, according to the article “Iron bioavailability and dietary reference values,” published in The American Journal of Clinical Nutrition, these fortified, elemental iron powders are not recommended by WHO and have much lower bioavailability than other, more natural sources. In fact these fortified sources of iron may only have 15% the bioavailability of native food sources!
Vegetarian whole foods (lower bioavailability): Leafy greens and other vegetables are excellent sources of micronutrients. When it comes to iron, however, studies consistently show that even nutrient-dense greens such as spinach are a “poor source of iron”. This is because vegetable sources do not pre-package the iron in readily absorbed forms of iron, such as hemoglobin (you may have heard of “nonheme iron”). According to the review article, “Iron bioavailability and dietary reference values,” overall bioavailability for Western-type vegetarian diets “ranges from 5% to 12%”. That's not to say vegetarian diets are necessarily deficient in iron, however. Legumes, for example, are an excellent source of ferritin, which has decent bioavailability--just not as much as meat (and insect) sources.
Meat (high bioavailability): In contrast to non-heme foods, heme sources of iron, such as shellfish, poultry, and beef, have about a 25% absorption rate. This is considered highly bioavailable.
Insects (high bioavailability): How do insects fair as sources of iron? This is where it gets tricky--and exciting. Like many other areas of nutrition, Western scientists tend to think in terms of a meat vs. non-meat dichotomy. With iron, nutritionists usually speak in terms of “heme” vs. “nonheme”, the former associated with meat, the latter with vegetables and other non-meat sources. Heme is preferable, while nonheme is less readily absorbed. However, new research may completely undermine the simplistic heme vs. nonheme way of thinking about bioavailable iron. In July of 2016, a landmark study by scientists in China demonstrated the absorption of iron from insects compared to meat (sirloin). After noting that “few insects have hemoglobin, and all are devoid of myoglobin,” they nevertheless contain highly bioavailable iron complex “in the form of ferritin, holoferritin, and cytochrome”. While legumes have ferritin, holoferritin and cytochrome appear to be unique to mammals and insects. Almost all of the insects they studied showed a higher iron solubility than sirloin, and most of them either outperformed or compared favorably to the absorption of iron from meat. This study confirmed earlier claims by nutrition scientists that insects are indeed a high quality source of bioavailable iron. In fact other case studies have shown that insects can be used to help to cure anemia by boosting hemoglobin levels in the body.
One serving of Chapul’s cricket flour contains 15% of the daily recommended intake for iron. Its chocolate and vanilla protein blends (a mix of insect and vegetarian ingredients) contain 28%.