Glucomannan and blood pressure:
Glucomannan-enriched biscuits (0.7 g/412 kJ [100 kcal] of glucomannan) or placebo of wheat bran fiber biscuits taken by subjects on medication and a low cholesterol diet every day for three weeks significantly improved blood sugar control by 5.7% measured by fructosamine (a measurement of long term glucose control and lowered systolic blood pressure by 6.9% but body weight, HDL, LDL, and total cholesterol, triglycerides, glucose, insulin, and diastolic blood pressure were not affected (40). It may be difficult to sort out in this study whether the benefit was due to diet, medication or glucomannan.
Other studies did not show any benefit of glucomannan in lowering blood pressure (41).