Previous animal and cell-based studies indicated that exposure to the common food additive carrageenan impaired glucose tolerance and increased insulin resistance. Carrageenan is widely used in processed foods to improve solubility, but predictably causes inflammation, which contributes to insulin resistance by inhibition of insulin signaling. To test if removal of carrageenan from the diet could reduce insulin resistance, we initiated a double-blinded, controlled feeding study in individuals with prediabetes, defined by Hemoglobin A1c values of 5.7%-6.4%. All procedures were approved by the University of Illinois at Chicago IRB. Participants were provided study diets for 12 weeks, which either contained or did not contain carrageenan, and had similar composition of protein, carbohydrate, and fat. An additional group was comprised of individuals who participated in study tests, but ate their usual diet. Subjects on study diets picked up their food weekly at UIC and had blood tests, including 2h glucose tolerance tests performed at entry, 6, and 12 weeks. Inflammatory parameters, including fecal calprotectin, were measured at entry and conclusion. Preliminary study results from 17 participants indicate that the carrageenan-free diet was associated with significant decline in hemoglobin A1c (p=0.004, unpaired t-test, two-tailed), HOMA-IR (homeostatic model for insulin resistance) score (p=0.0064), insulin resistance (p=0.02), and leukocyte phospho-serine IRS-1 (p=0.003) and NF-kappaB, compared to study participants on the control study diet or their regular diet. Study findings indicate significant decline in insulin resistance by removal of carrageenan from the diet. Additional studies of inflammatory parameters, immune cell subsets, and fecal microbiome are pending.


J.K. Tobacman: None.

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