To combat iron deficiency in Low and Middle-Income Countries, sustainable food-based solutions have to be implemented to serve populations, not only individuals. One solution is the introduction of iron biofortified staple crops on market level. Before market level introduction, the bioavailability of iron in the new biofortified Irish Potato (IP) breed needs to be assessed. In this study the investigator compares the fractional and total iron absorption after extrinsic stable isotope labelling of the new biofortified high iron IP variety and a normal market level IP variety. The study is conducted in Peruvian women of reproductive age with marginal iron status.

The 40 women enrolled will consume test meals consisting of 500g steamed and mashed high iron Irish potatoes labelled with Fe-58 daily for a period of 10 days and will then switch to the test meals consisting of 400g steamed and mashed control sweet potatoes labelled with Fe-57 for a period of 10 days. The order of test meal type is random. A baseline blood sample will be taken on the first meal feeding day prior to consumption of any test meals, study day 15 (before switching to the other test meal IP variety), on study day 26 (14 days after completion of the first test meal period) and on Day 40 (14 days after completion of the second test meal period). Erythrocyte incorporation of the stable isotope labels will be measured in these blood samples using an ICPMS and will be used to calculate fractional and total iron absorption from the two different type of test meals.

Inclusion Criteria:

1. Woman aged 18-25 years old.
2. Low/marginal iron status: serum ferritin (SF) ≤ 25 μg/L.
3. Normal BMI for age (18.5-25.0 kg/m2).
4. Weight less than 65 kg. We will give equal amounts of stable isotopes to each study participant and therefore need to set a limit on body weight in order to achieve measurable isotope enrichment in erythrocytes.
5. Willing and able to commute to the meal distribution/health centre site.
6. Able to understand and to sign written concept prior to trial entry.
7. Informed consent signed.
8. Prepared to use contraceptives for the duration of the study

Exclusion Criteria:

1. Severe anaemia Hb <107.2 g/L (adjusted for meters above sea level)
2. Inflammation/infection (CRP > 5 mg/100 ml).
3. Relevant digestive (intestinal, gastric, hepatic or pancreatic), renal, metabolic disease, and any other problem that will interfere with the study as determined by the screening visit and by self-report from the subjects.
4. Pregnant (urine test before entering the study) or breast-feeding.
5. Any medication or supplement which may impact iron metabolism.
6. Unwilling to discontinue vitamin and minerals supplements at least two weeks prior to the study start, as ascertained at the screening visit.
7. Significant blood losses over the past 6 months (i.e. trauma, major surgery, blood donation).
8. Subject who cannot be expected to comply with study procedures.
9. Presence of fever (>37.5 °C) on the first study day

Participant is non-blinded based on differences in meal option A and B, meal option A --> B or B --> A, is assigned through investigator randomisation.