A Low Glycemic Index Diet for Prevention of Glucose Intolerance During Bed Rest

Many medical conditions and interventions require periods of bed rest in order to maximize recovery and restore optimal physical function. Unfortunately, muscle becomes glucose intolerant, bone starts to break down, and arteries become stiffer during sustained periods of chronic inactivity, such as bed rest. Elevation of blood glucose during hospital stays results in increased morbidity, mortality, length of stay and costs. Components of the typical Western diet (refined carbohydrates and protein from animal sources common in hospital foods) induce glucose intolerance, bone catabolism, and arterial stiffening; plant-based proteins may not have the same negative impact. Pulses (i.e. low fat legumes: lentils, chickpeas, beans, peas) contain carbohydrate with a low glycemic index, and do not substantially increase blood glucose levels. At the same time, they are high in protein, but do not contain the same sulphur-containing amino acid profile as animal proteins that induce bone resorption. Pulses are, therefore, a potential 'super food' to mitigate many of the negative impacts associated with required bed rest following medical illness.

The study purpose is to determine the effects of a pulse-based diet compared to a Western diet of typical hospital foods on glucose tolerance, bone catabolism, and arterial stiffening during bed rest. The investigators hypothesize that a pulse-based diet will be superior to a typical Western diet for preventing glucose intolerance, bone catabolism, and arterial stiffening during sustained bed rest.

Six healthy adults will take part in a cross-over study where they will be randomized to four days of bed rest while on a pulse-based or Western diet, have a one month wash-out and then cross-over before another four days of bed rest with the other diet. Immediately before and after bed rest (i.e. the first morning after the last night of bed rest), oral glucose tolerance tests will be conducted to assess glucose tolerance and insulin sensitivity (i.e. markers used to assess diabetes risk). At the same time points, fasting blood samples will be collected for lipid assessments. Urine will be collected for assessment of bone catabolism (via measures of N-telopeptides: a by-product of collagen from bone which appears in the urine when bone is breaking down). Blood pressure will be evaluated every two hours during bed rest days from 9am to 9pm. Arterial stiffness (measured by the gold-standard technique of pulse wave velocity using applanation tonometry) and beat-by-beat blood pressure will be used to assess blood vessel function before and after four days of bed rest.

This study will inform improved hospital diets and nutritional habits of patients to prevent or offset negative health implications during periods of bed rest that may be required either in-hospital, long-term care or at home as part of standard medical care.