Biomarkers of Nutrition for Development (BOND)—Iron Review

Abstract

This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health.The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation.

Weighing the risks of high intakes of selected micronutrients compared with the risks of deficiencies

“…MN biomarkers can be categorized into markers of exposure, status, function, and effect, and they vary with respect to the range of MN status that can be detected. Consensus statements on the best biomarkers for the nutrients included in this paper have been published . Biomarkers of MN excess are available (Table ), but are generally less well characterized compared to biomarkers of deficiency, particularly in terms of linking these biomarkers with functional or clinical symptoms of toxicity.…”

“…Consensus statements on the best biomarkers for the nutrients included in this paper have been published. [10][11][12][13][14][15][16] Biomarkers of MN excess are available ( Table 2), but are generally less well characterized compared to biomarkers of deficiency, particularly in terms of linking these biomarkers with functional or clinical symptoms of toxicity.…”

“…These predictions can then be confirmed with targeted assessments using specific biomarkers of MN status. 10 Quantifies liver vitamin A stores, though no consensus on total body stores or hepatic concentrations indicating toxicity; unknown if affected by inflammation Breast milk vitamin A 10 Not homeostatically controlled, so may indicate excessive exposure Folic acid Unmetabolized folic acid 11 No clear relationship between biomarker and clinical adverse effects Iron Ferritin 16 Can indicate high iron stores in the absence of inflammation Serum iron, transferrin saturation, and total iron binding capacity (TIBC) 16 Can indicate high iron stores in the absence of inflammation Non-transferrin-bound iron (NTBI) 106 Represents the form of circulating iron likely to cause oxidative damage Zinc Plasma copper; ceruloplasmin activity 26 No clear relationship between biomarker and clinical adverse effects…”

Impacts of Mainstream Hydropower Development on Fisheries and Human Nutrition in the Lower Mekong

“…EARs for iron range from 2.2 to 42.8 mg/day (World Health Organization (WHO) Food Agriculture Organization (FAO) of The United Nations, 2004), depending on age sex, and iron availability in the diet. The capability of the body to absorb iron is controlled by a range of factors, including foods and nutrients eaten with the iron in the same meal (e.g., ascorbic acid, calcium, or polyphenols), the type of iron consumed (heme or non-heme iron), as well as each person's overall iron status or concurrent disease load (Lynch et al, 2018). However, we do not have sufficient data for several of these factors within GENuS (polyphenols, alcohol) to allow for explicitly calculating the absorbable iron supply from the diet.…”

The neonatal period: A missed opportunity for the prevention of iron deficiency and its associated neurological consequences?

“…• Most direct effect of iron is thought to be on the synthesis of the monoamine neurotransmitters, dopamine, serotonin and norepinephrine (Lynch et al 2018). Monoamine synthesis begins in mid-gestation, until about 3 years of age.…”