On Nutrition

DEAR DR. BLONZ: Soon after eating something sweet or starchy, I become a bit groggy with an urge to doze off. When out, I can fight it, but sometimes I get nervous and shaky. A friend said that I might have “reactive hypoglycemia,” but I thought those theories were discounted decades ago. -- S.T., Oakland, California

DEAR S.T.: Sugars and other carbohydrates are a source of energy for the body, but they can also be associated with drowsiness, and even, ironically, with the shakiness you describe. One possible explanation is the way simple sugars affect the body and the brain, coupled with inadvertent miscues we give the body through the way we eat.

The body needs to maintain its blood glucose level within narrow limits to keep metabolism on an even keel. Multiple systems kick into gear if glucose gets too high or too low. All the digestible carbohydrates we eat are broken down to simpler sugars, and most end up as glucose in the blood. If it’s from a balanced meal, glucose will rise at a moderate level, but the rise can be rapid if the glucose comes from sweets or a can of soda -- especially if consumed on an empty stomach.

Rising blood glucose is the “I am fed” signal; this then causes insulin to be released by the pancreas. Insulin is the hormone that facilitates the exit of glucose from the blood into the cells, where it provides energy to perform work, build new tissue or create needed substances. A potential connection with drowsiness is the fact that elevating blood glucose and insulin release is paired with the production of relaxation-inducing substances in the brain. (This helps explain the urge to “veg” after a big meal.) The situation becomes more complex in those with Type 2 diabetes, as there can be “insulin resistance” where normal levels of insulin are unable to produce the needed blood-glucose-lowering effect.

You mentioned reactive hypoglycemia, which, although not as common as it was once thought, can develop in some individuals. Reactive hypoglycemia occurs when the body releases too much insulin for a given amount of glucose in the bloodstream.

When blood glucose drops too low, a defense mechanism gets triggered. A hormone involved in this process is adrenaline: the body’s “fight or flight” hormone. Aside from helping provide a small amount of glucose (stored in the liver), adrenaline also revs up the body’s muscles and gets them ready for action. Under the influence of adrenaline, you can feel your heart -- a muscle -- pounding in your chest as it pushes blood into the working muscles to prepare them for action. It is not a pleasant sensation, and the nervousness and shakes you mention could be connected to this phenomenon.

You don’t say much about your general health. I have tried to outline some basic issues, but one certainty is that you need to contact a medical doctor to find out what is going on in your body. There are tests that can provide answers, and it is in your best interest to find out ASAP.

In the meantime, try to stay off the sweet stuff -- especially on an empty stomach.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

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