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

Authors: HARRIS, SUSAN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; DAWSON-HUGHES, BESS - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Endocrine Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2010
Publication Date: 10/1/2010
Citation: Harris, S., Dawson-Hughes, B. 2010. No effect of bicarbonate treatment on insulin sensitivity and glucose control in non-diabetic older adults. Endocrine Journal. 38(2):221-226.

Interpretive Summary: Typical Western diets cause excess acid production in the body. The ability to excrete this excess acid declines with age due to gradual declines in kidney function. This results in a common condition called mild metabolic acidosis that can have adverse effects on bone and muscle. Some evidence suggests that metabolic acidosis may also increase the risk for type 2 diabetes by impairing tissue uptake of glucose (i.e. causing insulin resistance). We studied 153 non-diabetic adults aged 50 and older who had been randomly assigned to four treatment groups, two of which involved bicarbonate supplementation (bicarbonate is an alkalinizing agent) and two of which did not. We compared changes in insulin, glucose and HOMA-IR, an index of insulin resistance, after three months of bicarbonate or no-bicarbonate supplementation. As expected, bicarbonate significantly reduced acid excretion. However we observed no effect of bicarbonate supplementation on insulin, glucose, or HOMA-IR. These findings suggest that bicarbonate supplementation in the dose studied (67.5 mmol/d) is unlikely to reduce the risk of type 2 diabetes in non-diabetic adults aged 50 and older.

Technical Abstract: 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 three-month clinical trial of bicarbonate supplementation to improve indicators of bone and muscle health. 153 ambulatory, non-diabetic adults aged 50 and older were studied. Subjects were randomized to one of two bicarbonate groups (67.5 mmol/d of potassium bicarbonate or sodium bicarbonate) or to one of two no-bicarbonate groups (67.5 mmol/d of placebo or potassium chloride). Subjects remained on treatment throughout the three-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.