INTRODUCTION
The global burden of diabetes is on the rise. The World Health Organization (WHO) estimated that 422 million adults were living with the disease in 2014, a number that has nearly doubled since 1980 (22). Sustained hyperglycemiaultimately increases one’s susceptibility to cardiovascular disease and other health complications. It seems pertinent to investigate therapies which may lessen the disease burden of diabetes at the individual and population level.
The earliest experimental studies of vinegar’s health benefits demonstrated that acetic acid and vinegar have inhibitory effects on the rapid increase in blood glucose concentrations following sucrose ingestion (7). Ebihara et al investigated blood glucose and insulin responses to a 300ml sucrose solution with and without the addition of 60ml strawberry vinegar (5% acetic acid). Notably, the time to attain maximal glycemic response was delayed in the vinegar condition. Furthermore, the area under the insulin response curve was 20% smaller in the vinegar-containing test meal. These early experimental studies provided evidence that vinegar may exert potent anti-glycemic effects when consumed with a glycemic load.
The antiglycemic benefits of vinegar have been demonstrated in healthy subjects with normal glucose control (3,8,18) and insulin-resistant subjects (11,21). Those with impaired glucose tolerance or insulin resistance have shown long-term supplementation with vinegar reduced HbA1c values by 0.16% (21) and improved insulin sensitivity by 34% via a mechanism proposed to work similar to the drug metformin (11). A dose-response relationship for blood glucose and serum insulin concentrations after a bread meal have been observed, noting that 28 mmol acetic acid significantly lowered blood glucose and insulin compared to lower doses (18). In fact, the ability of vinegar to lower postprandial glucose excursions may be its most potent quality, as isolated postprandial hyperglycemia has been demonstrated to increase CV mortality, even in the absence of impaired fasting glucose.
Aerobic exercise is well-known to benefit glucose control. (6,7,9) Research has shown duration and timing (pre-vs. post meal) of exercise to be factors in the extent to which glucose is controlled. Dipietro et al. observed that a single bout of 15 minutes of walking performed 30 minutes post-meal was effective in improving 24-hour glycemic control in insulin resistant subjects and reducing glucose levels 3 hours post-meal (6). This highlights the need to verify if pre-meal exercise can benefit postprandial glucose.
Currently, the efficacy of pre vs. postmeal walking has not been established. No studies to date have compared a bout of post-meal walking with other glucose control strategies such as pre-prandial vinegar ingestion. Therefore, the aim of the present study was to compare the efficacy of a mass-relative dose of pre-prandial vinegar to a 15-minute bout of self-paced treadmill walking in reducing postprandial response to high-glycemic meal in glucose-intolerant participants. We hypothesized that 15 minutes of postprandial walking and preprandial vinegar ingestion would both reduce postprandial glycemia. However, we expected that a larger reduction would be observed with postprandial walking.