Resistant Potato Starch to Alleviate GWI

Inclusion Criteria: 1. Ability to provide informed written consent 2. Willing to comply with all study procedures and be available for the duration of the study (including providing stool samples) 3. Meeting the modified Kansas GWI case definition\* with gut symptoms endorsed 4. Deployed to Persian Gulf during Operations Desert Storm or Desert Shield56.Aged 50-85 years old * Moderate to severe GWI symptoms lasting at least 6 months in a minimum of three of the six symptom domains (one of which must be fatigue). The symptom domains are: * Pain (joint pain, muscle pain) * Gastrointestinal (diarrhea, nausea, vomiting, cramping) * Respiratory (persistent cough, wheezing) * Skin (rashes) * Fatigue (sleep problems, fatigue) * Neurologic (memory problems, headaches, dizziness, mood changes) Exclusion Criteria: 1. A Known SARS-CoV-2 infection in the last 60 days and/or with a diagnosis of post-acute sequelae of COVID-19 (PASC, sometimes called long COVID) defined as COVID-19 symptoms lasting for greater than 6 months. 2. Subjects identified as, or appearing to, lack consent capacity 3. Alcohol abuse (greater than 14 drinks per week for men and 7 drinks per week for women) 4. Use of investigational drugs, biologics, or devices within 30 days prior to randomization. 5. Individuals who are pregnant, lactating or planning on becoming pregnant during the study. 6. Diagnosed inflammatory bowel disease, Crohn's disease, or Celiac's disease 7. Uncontrolled/untreated hypothyroidism 8. Previous gastrointestinal surgery (colorectal surgery, gastric bypass, intestinal resection) 9. Systemic antibiotics in the last 30 days 10. Fecal microbiota transplant in the last 30 days 11. Active dysphagia 12. Allergies to any of the ingredients in MSPrebiotic 13. Use of immunomodulatory medications in the last 30 days 14. Any other factor, condition, or medication not listed above the Investigators believe will affect the response in the gut or the interpretation of results.