The primary objective is to assess the impact of three months' treatment with pre-/probiotic mix on markers of nephropathy and other comorbidity related to diabetes. A double blinded, randomized, placebo-controlled crossover, single-centre study including 46 patients with type 1 diabetes and albuminuria. The treatment period is 2 x 12 weeks with 6 weeks washout. The primary outcome is to evaluate the effect of pre-/probiotic mix on albuminuria.

Recent data has pointed towards a link between gut microbiota and chronic kidney disease (CKD). It is hypothesized that defects in the intestinal barrier due to intestinal dysbiosis, a microbial imbalance in the intestines, allow bacterial toxins and other proinflammatory substances to pass and cause systemic inflammation that damages the endothelium. To reestablish the microbial symbiosis and thereby strengthening the gut barrier different treatments have been investigated. Fibers serve as substrate for the beneficial bacterial strains and probiotics are selected bacteria that exert a beneficial effect on the gut environment. It is hypothesized that a supplement of fructo-oligosaccharides and probiotics (Pre-/probiotic mix) will strengthen the gut barrier and thereby protect the endothelium and kidneys.

The aim of this study is to test whether af Pre-/probiotic mix, will have a beneficial impact on albuminuria in persons with type 1 diabetes and albuminuria.

46 patients with type 1 diabetes and albuminuria will be recruited from Steno Diabetes Center Copenhagen (SDCC) in accordance with the study in- and exclusion criteria.

Inclusion Criteria:

1. Persons ≥ 18 years of age with a diagnosis of type 1 diabetes (age at onset <40 years; permanent insulin treatment initiated within 1 year of diagnosis)
2. Albuminuria: UACR > 30 mg/g (in ≥2 out 3 morning spot urine collections prior to randomization)
3. Participants must be on stable renin-angiotensin system blocking treatment 4 weeks before start of study drug and throughout study duration.
4. Able to understand the written participant information and give informed consent

Exclusion Criteria:

• 1. Non-diabetic kidney disease indicated by medical history and/or laboratory findings 2. Known inflammatory bowel disease (IBD) 3. IBD symptoms due to investigator's opinion 4. Known celiac disease 5. Existing ostomy, malabsorption, history of bowel resection or bariatric surgery.

  6. Heart valve replacement or history of endocarditis 7. Known rheumatic disorders treated with anti-inflammatory agents 8. Known hyperthyroidism or hypothyroidism 9. Active immunosuppressant therapy with systemic effect due to investigator's opinion 10. Current cancer treatment or within five years from baseline (except basal cell skin cancer or squamous cell skin cancer) 11. eGFR<15 ml/min/1.73m2, dialysis or kidney transplantation 12. Active antibiotic therapy until 30 days ahead of screening 13. Dietary supplements containing fibers (e.g. psyllium), probiotics or carotenoids until 30 days ahead of screening 14. The receipt of any investigational product 90 days prior to this trial 15. Unable to participate in study procedures 16. Any clinically significant disorder, except for conditions associated with type 1 diabetes, which in the Investigators opinion could interfere with the results of the trial 17. Pregnancy or lactation 18. Participation in another intervention study

Allocation will be masked for both participants and investigators. Only after completion of all study visits by all participants and after database lock the randomization code will be opened.