Fibers are broadly classified as soluble and insoluble based on their physical or analytical properties. Two human studies have been carried out in this laboratory utilizing soluble gums. The first compared a low fiber diet to the diet with an average of 19.5 g of added fiber per day from cellulose, an insoluble fiber, or carboxymethylcellulose gum, karaya gum or locust bean gum, all soluble fibers. Plasma cholesterol levels but not triglycerides were significantly lower when the soluble gums were consumed for 4 weeks each. Glucose and insulin response curves after a standard glucose tolerance test were not significantly different between the 5 diets. Adding refined fibers to the basal diet did not significantly affect apparent mineral balance of calcium, magnesium, manganese, iron, copper or zinc, with the exception of a negative manganese balance after carboxymethylcellulose. The second study added an average of 31.7 g of guar gum per day to the diets of non-insulin dependent diabetic individuals for 6 months. Lipid levels observed at the beginning of the study were not reduced in either group, placebo or guar gum supplemented. Consumption of guar gum significantly reduced the C-peptide but not the glucose response curve. The number of insulin receptors increased while affinity remained the same. Apparent mineral balance was not affected by the consumption of guar gum for 6 months. The combined results of these studies indicates that soluble refined gums may have therapeutic value in reducing cholesterol and improving glucose metabolism without adversely affecting most mineral balances.