Sugar cravings are relatively common and can occur for a number of different reasons. Certainly sugar cravings can occur following exercise, and such cravings are the natural response to physical activity that can deplete the glycogen stores of the skeletal muscle. Physical activity also increases the sensitivity of skeletal muscle to insulin. These factors cause blood sugar to pass into the muscle and lowering blood sugar levels. This causes a feedback signal to the hypothalamus to stimulate the consumption of carbohydrate foods in order to both maintain blood sugar and to allow the subsequent resynthesis of glycogen. Such cravings are not detrimental because they are a requirement of normal blood sugar regulation and result in the maintenance of glycogen stores. However, some individuals develop sugar cravings without the performance of physical activity. Such people often find their sugar cravings are for particular low quality foods and these foods may as a result be over consumed leading to weight gain.
L-glutamine is an amino acid that has shown some success at treating these sorts of idiopathic sugar cravings. Only about 40 % of L-glutamine is a is absorbed in humans due to most being used by enterocytes as a source of fuel. Following absorption, plasma levels rise as the remaining L-glutamine passess into the blood. The exact reason why L-glutamine is effective at preventing sugar cravings is not known, but may relate to the ability of L-glutamine to be deaminated and the carbon skeleton used as a precursor for gluconeogenesis. In this way L-glutamine allows the production of new glucose in the liver, which enters the circulation and raises levels of blood glucose. As blood sugar levels rise, the hypothalamus down regulates the cravings for sugar. In addition, L-glutamine may enter the central nervous system directly where it functions as a neurotransmitter. This may decrease the cravings for sugar directly. L-glutamine is safe, and doses of around 2 to 5 grams per day may reduce sugar cravings.