No effect of bicarbonate treatment on insulin sensitivity and glucose control in non-diabetic older adults

Chronic mild metabolic acidosis is common among older adults, and limited evidence suggests that it may contribute to insulin resistance and type-2 diabetes. This analysis was conducted to determine whether bicarbonate supplementation, an alkalinizing treatment, improves insulin sensitivity or glucose control in non-diabetic older adults. Fasting blood glucose and insulin were measured in stored samples from subjects who had completed a 3-month clinical trial of bicarbonate supplementation to improve indicators of bone and muscle health. One hundred and fifty three ambulatory, non-diabetic adults aged 50 years and older were studied. Subjects were randomized to one of two bicarbonate groups (67.5 mmol/day of potassium bicarbonate or sodium bicarbonate) or to one of two no-bicarbonate groups (67.5 mmol/day of placebo or potassium chloride). Subjects remained on treatment throughout the 3-month study. The primary outcome measures were changes in fasting plasma glucose, serum insulin and HOMA-IR, an index of insulin resistance. Bicarbonate supplementation reduced net acid excretion (adjusted mean±SEM for the change in NAE/creatinine, mmol/mmol, was 0.23±0.22 in the no-bicarbonate group compared with -3.53±0.22 in the bicarbonate group, P<0.001) but had no effect on fasting plasma glucose, serum insulin, or HOMA-IR. In conclusion, bicarbonate supplementation does not appear to improve insulin sensitivity or glucose control in non-diabetic older adults.