The human body needs iron to function properly. It can cause anemia, low energy, and heart palpitations. Children can be affected by iron deficiency for a long time.
Iron must be bioavailable for a person to absorb enough of it from the foods they eat.
What is bioavailability?
Nutrient bioavailability is the amount of nutrients that are absorbed by our body after they have been consumed in food.
Susan Fairweather Tait, professor of human nutrition at the University of East Anglia, explains: "It's a description of the ability of a micronutrient source to contribute to the physiological needs of that micronutrient."
She told us that bioavailability, especially of iron, can be measured. For iron, one can directly measure utilization. Frenchbioavailability) as the percentage of incorporation of an isotopically labeled dose of iron into hemoglobin (whereby 80 % of the absorbed iron is incorporated into hemoglobin).
What factors affect bioavailability?
Bioavailability in foods varies widely. Jeannine Baumgartner is a lecturer at King's College London specializing in nutritional sciences. She says the bioavailability of iron in foods varies widely.
Heme iron found in animal foods is more bioavailable than non-heme iron found in plants. She told us that absorption studies indicate that the bioavailability of heme iron is between 15 and 40 %.
Baumgartner states that the bioavailability of iron in non-heme foods and flour products may be affected by the presence or absence of iron absorption inhibitors, such as polyphenols and phytic acids. Iron absorption promoters include vitamin C, organic acid, and phytic and acetic acid.
Iron bioavailability can be affected by a person's iron status. Fairweather-Tait says that when a person is iron deficient, absorption pathways are more "upregulated," meaning iron is more likely to come from anywhere. When iron is abundant, it's the opposite.
For iron, the usual method is to measure its relative bioavailability. (To eliminate any confounding effect of iron status.)
Baumgartner says that consuming non-heme iron with vitamin C can improve bioavailability. You should also avoid non-heme iron, which contains inhibitors like polyphenols and phytic acids.
Processing methods can also increase iron bioavailability. Sauerkraut, sourdough, and other lactic acid fermented foods can increase iron bioavailability. Phytase can also be used to dephytinize grains and beans.
Can enrichment affect bioavailability?
Iron fortification does not increase bioavailability and may even decrease it if the amount is large enough. Fortification can still result in more iron being absorbed by the body, simply because it is more available.
Fairweather-Tait, a FoodNavigator contributor, said that while there is a "dose-response" effect in which % absorption and bioavailability would decrease with increasing dose, the amount actually absorbed into the system (and used to perform physiological functions) is higher.
She told us that it is possible to add iron to foods without interacting with inhibitors. Phytate is the most common. It is used by countries that consume a lot of cereals.
Baumgartner explained that foods are often fortified with non-heme ferrous oxide, which is susceptible to similar factors in terms of bioavailability as natural iron.
The bioavailability of iron-fortified foods is also affected by the chemical form the iron compound added to the food takes. Food manufacturers don't choose the compound based solely on its bioavailability; they also consider how it will affect the color and taste of the food. She explained that water-soluble iron compounds are more easily absorbed, but they can also cause unwanted changes in color or flavor.
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