The first aim of this study is to investigate if daily administration of the prebiotic Synergy-1 (a commercial product consisting of oligofructose-enriched inulin) together with a common iron supplement (ferrous sulphate) during 4 weeks, in premenopausal non-anaemic women with low ferritin levels, would mitigate the adverse effects of iron on the gut microbiota. The estimated absorption rate of the ferrous salts is 10-15%, therefore the unabsorbed iron will reach the colon where it could stimulate growth of non-beneficial bacterial species in the intestinal environment. By contrast, prebiotics function by specifically supporting growth of the typically-beneficial microorganism such as bifidobacteria. Inulin-type fructans (ITF) are well recognised in this way. The hypothesis to be tested is that prebiotic consumption will lead to a beneficial shift in the microbiota helping against the dysbiosis associated with iron supplementation.

This will be a crossover, placebo controlled, and randomised pilot study in 15 pre-menopausal female individuals with ferritin levels below 40 mcg/l but normal hemoglobin (Hb) and C reactive protein (CRP). The study will last 12 weeks and consist of two separated 4-week randomised intervention treatment periods with a prebiotic (Synergy-1) or placebo (Maltodextrin) in combination with an iron supplement (FeSO4) separated by a 4-week wash-out period. Volunteers will take daily doses of an iron supplement and a prebiotic (Synergy-1) or placebo (Maltodextrin) during the trial excepting in the washout period where the iron supplement and prebiotic/placebo treatments will be discontinued.

This trial will investigate the effects of an iron supplement treatment in combination with a prebiotic food supplement or placebo food supplement. Participants will be required to take one daily tablet of a generic, iron supplement (200 mg FeSO4 equivalent to 65 mg iron) (provided by pharmacy). In addition, participants will be required to take one of the products (prebiotic or placebo) daily at the same time each day. The prebiotic food supplement (supplied by the Beneo company) is a chicory inulin powder produced in Belgium. It has been used in scores of human intervention studies with no adverse effects. Participants will be required to take one 7 g sachet of prebiotic food supplement daily. This will be reconstituted with water and participants will be encouraged to take the sachet at the same time each day. The placebo control food supplement will be maltodextrin. Maltodextrin is a standard placebo product for use in human studies involving prebiotics and has been used safely at this dose, in many trials by ourselves for the last 20 years. The products will be provided as a powder (served in sachets) and identical in texture and appearance. The Beneo company will produce and provide barcoded sachets, blinded to the investigators and volunteers. After all volunteers have completed their study visits and all samples have been analysed by researchers, Beneo will provide information about barcoded sachets. Compliance to food supplement (prebiotic or placebo) will be assessed by recording intake in gastrointestinal (GI) diaries and participants will also be asked to return any unused sachets to the researchers at the end of the each 4-week intervention periods. For participants to be considered compliant and therefore included in the study, they will be required to take the food supplement or placebo at least 6 out of every 7 days of the trial for the week period and return completed questionnaires.

Inclusion Criteria:

• Age: 18-50 years
• Gender: Female
• Volunteers agree to sign an informal written consent form
• General good health
• Have ferritin levels below 40 mcg/l
• Normal or borderline-low hemoglobin levels (>11.5g/dL)

Exclusion Criteria:

• Use of antibiotics, prebiotics or probiotics (in food products or as supplements), laxatives, anti-spasmodic, anti-diarrhoea drugs, (e.g. Orlistat, Lactulose) in the last 4 weeks prior to, or during the study period.
• Use of any iron supplement in the last 6 months prior to the study period.
• If participants have received bowel preparation for investigative procedures in the 4 weeks prior to the study.
• Surgical resection of any part of the bowel.
• If participants are taking any medication whose effectiveness could be reduced by the iron administration (e.g. Levodopa, Levothyroxine).
• If participants have any chronic gut disorder/disease, such as inflammatory bowel syndrome (IBS), inflammatory bowel disease (IBD), etc. or other conditions that might affect the gut environment, e.g. coeliac disease.
• If participants are taking any medication that could affect the iron absorption (e.g. lansoprazole, omeprazole).
• If participants are pregnant or are lactating.
• If participants have a body mass index (BMI) > 30 kg/m2.
• Severe allergy or any history of severe abnormal drug reaction, drug or alcohol abuse.

Anonymised data of faecal bacterial DNA may be made available to The European Bioinformatics Institute. This will help support other research in the field