Magnesium may shield against colon cancer in genetically At-Risk individuals

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Hyperplastic polyp or/and Adenoma cases * Polyps free participants with any of the following high risk of colorectal polyps or cancer: (1) family history of colorectal cancer or polyps; (2) current cigarette smoker; (3) obesity (BMI≥30 kg/m2); (4) low intake of fiber (lowest fiber intake quartile: daily intake \<16.6g); (5) high intake of red meat and well-done or processed meat (mutageneity index ≥5852). * Participants from the TCPS (IRB # 090235), the TIARS (IRB # 090235), from Vanderbilt University Hospital or from other resources * Consent to be contacted for future studies in TCPS (IRB # 020462), TIARS (IRB#090235) * Participants with a calcium intake ≥ 700 mg/day measuring with 24 hour dietary recalls * Participants with a calcium intake \< 2000 mg/day measuring with 24 hour dietary recalls * Participants with a calcium/magnesium intake ratio \> 2.6 * Participants with known genotype for Thr1482Ile polymorphism in TRPM7 * Will live in Nashville or surrounding area in the next 6 months Exclusion Criteria: * Intolerance to magnesium glycinate or microcrystalline cellulose (placebo) * Chronic renal diseases and hepatic cirrhosis * Chronic ischemic heart disease with unstable angina, chronic heart failure at class III or IV and acute myocardial infarction in the last 6 months * Chronic diarrhea * Current breastfeeding * Current or planned pregnancy * Type I diabetes mellitus * Pituitary dwarfism * Use of digoxin and licorice * Current use of blood anticoagulant drugs such as Dicumarol(Warfarin), Clopidogrel (Plavix), Prasugrel HCl (Efficent), Ticlopidine (Ticlid), Lovenox (Enoxaparin), Fragmin (Dalteparin), Innohep (Tinzaparin), Eptifibatide (Integrilin), Tyrofiban (Aggrastat), and Abciximab (Reopro) * Current use of lithium carbonate therapy (Eskalith, Lithobid, Lithonate, Lithotabs, Apo-Lithium carbonate, Apo-Lithium carbonate SR, Carbolth, Duralith, PMS-Lithium carbonate, PMS-Lithium citrate) * Individuals with a history of colon resection or colectomy due to any reason * Individuals with any history of cancer other than non-melanoma skin cancer * Individual with history of any organ transplantation * Individual with a history of gastric bypass due to any reason * Individuals with Inflammatory bowel disease * Individuals if creatinine clearance is \< 50 * Currently institutionalized * Homeless individual (address, telephone etc.) * Unable to provide informed consent * Any condition that in the opinion of the investigator raises concerns about protocol compliance