The aim is to investigate the mechanism by which galacto-oligosaccharide acutely increases iron absorption by using stable isotope appearance curves. This will allow the evaluation of changes in serum iron isotopes over the first few hours after administration of the iron supplement and provides information where and in what amount iron absorption takes place in the GI-tract.

Iron is an important mineral in our body and fulfills essential functions such as for example oxygen transport from the lungs to the tissues. Iron deficiency is still the most common and widespread nutritional disorder in the world according to WHO. Common iron supplements all have their limitations in terms of availability and compatibility. Prebiotic fibers, such as galacto-oligosaccharides (GOS), selectively enhance growth of beneficial colonic bacteria. Prebiotics in general enhance the production of short-chain fatty acids (SCFAs) and thereby decrease luminal pH. Through the reduction in pH, prebiotics can enhance absorption of minerals such as calcium and magnesium and they have been proposed to potentially improve iron absorption.

In a recent iron absorption study in adult women with low iron stores in the laboratory of human nutrition ETH zurich, it was found that 15 g of GOS given with an iron supplement in the form of iron fumarate acutely increased iron absorption when given with water and a bread based meal. The dose of 15 g of GOS was tolerated well by the participants. As a follow up to the study, the aim of the current study is to investigate the mechanism by which GOS acutely increases iron absorption by using stable isotope appearance curves. This will allow the evaluation of changes in serum iron isotopes over the first few hours after administration of the iron supplement and provides information where and in what amount iron absorption takes place in the GI-tract.

Inclusion Criteria:

• Female, 18 to 45 years old
• SF levels 15-30 µg/L
• Normal body Mass Index (18.5-24.9 kg/m2)
• Body weight <70 kg
• Signed informed consent

Exclusion Criteria:

• Severe anaemia (Hb < 80 g/L)
• Elevated CRP >10.0 mg/L
• Any metabolic, gastrointestinal kidney or chronic disease such as diabetes, renal failure, hepatic dysfunction, hepatitis, hypertension, cancer or cardiovascular diseases (according to the participants own statement)
• Continuous/long-term use of medication during the whole studies (except for contraceptives)
• Consumption of mineral and vitamin supplements within 2 weeks prior to 1st supplement administration, including pre- and-or probiotics supplements (excluding foods and beverages with life cultures such as yoghurt, raw milk cheese and kombucha)
• Blood transfusion, blood donation or significant blood loss (accident, surgery) over the past 4 months
• Difficulties with blood sampling
• Use of antibiotics over the past month
• Known hypersensitivity to iron supplements in the given amount, GOS, or lactose
• Women who are pregnant or breast feeding
• Women who intend become pregnant during the course of the study
• Lack of safe contraception, defined as: Female participants of childbearing potential, not using and not willing to continue using a medically reliable method of contraception for the entire study duration, such as oral, inject-able, or implantable contraceptives, or intrauterine contraceptive devices, or who are not using any other method considered sufficiently reliable by the investigator in individual cases
• Known or suspected non-compliance, drug or alcohol (more than 2 drinks/day) abuse -
• Smokers (> 1 cigarette per week)
• Inability to follow the procedures of the study, e.g. due to language problems, self-- reported psychological disorders, etc. of the participant
• Enrollment of the investigator, his/her family members, employees and other dependent persons

Only female participants are being studied