Iron absorption and obesity by Dr. Omar Obeid

Today, the world faces huge health challenges from the burdens of obesity, iron deficiency (ID), and iron deficiency anemia (IDA). Studies indicate a strong association between obesity, inflammation, and low iron absorption. The underlying mechanism, which could lead to the development of anemia if left unresolved, remains unclear. The type of body fat distribution (central vs. peripheral) is known to affect the level of inflammation, although the impact of body fat type on iron absorption rate has not yet been studied.​

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Dr. Omar Obeid (NFSC, FAFS) and a team of investigators from FM and FHS at AUB collaborated with Prof. Michel Zimmermann from ETH Zurich on a study entitled “The relation between adiposity, inflammation, glycaemia and iron absorption: A comparison between central and peripheral adiposity”. 

The primary aim of the study was to test the effect of different body fat distributions on the rate of iron absorption in a sample of 125 premenopausal Lebanese women with varied Body Mass Index (BMI) levels. The levels of inflammation and glycemic biomarkers were determined, and the relationship between insulin sensitivity and iron absorption, an area not yet extensively explored, was investigated. 

The two major approaches to measure in vivo iron absorption are 1) the oral iron absorption test (OIAT), and 2) the level of iron stable isotope enrichment in the blood two weeks after the ingestion of a labeled dose. The latter is more technically demanding and time consuming, as it requires using Mass spectrometry over a two weeks period to determine the enrichment. Unfortunately, these methods have never been determined concomitantly to assess their comparability. In this study, OIAT and labeled stable iron isotope were incorporated with oral glucose tolerance test (OGTT).

Anthropometric measurements (weight, height, waist circumference) and body composition using DEXA were collected. Subjects fasted overnight and then were given oral glucose-iron loads (75g of glucose, 100mg of iron in the form of Sodium Ferrous Citrate, and 6 mg FeSO4 of labeled iron isotope 57Fe). Blood samples were collected at baseline, 2 hours post iron and glucose load, and 2 weeks post labelled iron load. Blood samples will be analyzed for levels of iron, glycaemia, insulin, and inflammatory parameters. A high level of stable isotope in red blood cells would indicate high iron absorption; on the other hand, a high level of hepcidin, a major inflammatory marker, is inversely related to iron absorption. 

The study is a registered clinical trial funded by AUB-URB and ETH Zurich. Data collection took place between 2016 and 2018 at AUB and AUBMC, and analysis of the results is underway at AUB. The analysis of stable isotope and some inflammatory markers will take place at ETH. The investigators are currently measuring the changes in hepcidin at 2 hours post iron and glucose load to assess whether hepcidin production is affected by insulin sensitivity in order to explore the relation between insulin and hepcidin production. 

According to Dr. Obeid, the results of this study may guide physicians in how to manage iron deficiency, helping with decisions of whether or not to prescribe iron supplements. “If people don’t absorb the iron that they are consuming from the food, and ingest extra iron from supplements, then the iron would reach the intestine and alter the microbiota, leading to inflammation”, concluded Dr. Obeid.