The lowdown on low blood sugar

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"No thanks. If I eat anything with sugar in it, my blood sugar drops too low and I feel really weak."

"I have to eat every few hours. I have hypoglycemia, and if l go too long without food, I get sick."

Chances are you've heard--or overheard--someone explaining that he or she suffers from hypoglycemia, or low blood sugar. Or maybe you've wondered if you have the condition yourself. But hypoglycemia is "vanishingly infrequent" in the general population, says Philip Cryer, MD, a blood sugar specialist at the Washington University School of Medicine in St. Louis as well as president-elect of the American Diabetes Association. It affects far less than one percent of healthy people.

So why do so many believe they are afflicted with it? It's largely because many general "symptoms" people experience for all kinds of reasons resemble certain hypoglycemic symptoms--weakness, fatigue, stress, headache, a "pit" in the stomach. The vague nature of these symptoms has led even the medical community to over-diagnose the condition. As recently as 10 years ago, patients who came to doctors' offices complaining of exhaustion and anxiety were often suspected to be suffering from hypoglycemia. And physicians sometimes "confirmed" their diagnosis with tests to check for low blood sugar. But there's more to true hypoglycemia than the garden-variety symptoms of malaise or tiredness, and proper diagnosis requires a different type of blood sugar test than the one that was usually administered.

The facts behind the hypoglycemia hype
In truth, most people's systems are remarkably adept at maintaining a fairly steady blood sugar level. The mechanism works as follows.

Soon after a meal, the level of sugar in the blood starts to go up. That's because the food we eat is broken down into a type of sugar called glucose, which makes its way into the bloodstream. As blood sugar rises, the pancreas responds by releasing the hormone insulin, which allows glucose to leave the bloodstream and enter our various tissues, where it fuels the body's activities. Some sugar is alSO taken up by the liver and stored there for later use. Then, when the sugar supplied by the last meal is more or less used up and we officially go from a "fed" to a "fasting" state, insulin levels drop, which keeps the sugar in the blood from falling further. In addition, stored sugar is released from the liver back into the bloodstream with the help of a hormone called glucagon.

This smooth shifting of sugar into and out of the bloodstream is crucial; the various body cells, particularly those of the brain and the rest of the central nervous system, must receive a steady, consistent supply of sugar from the blood to function properly. Even when we start to get hungry, either because we haven't eaten for many hours or because our last meal was small, the blood sugar concentration remains relatively constant--usually somewhere between 60 and 100 (milligrams per deciliter of blood).

In a small number of people, however, the system misfires and blood sugar can fall too low. It may be because insulin "overshoots the mark" and takes too much sugar out of the blood at the wrong time. Or it could be that glucagon is not doing a good enough job of getting stored sugar out of the liver.

If the blood sugar falls too low within two to five hours of eating, the result is a type of hypoglycemia that many physicians refer to as reactive hypoglycemia (so named because the body is reacting to food). Specifically, the sugar level falls low enough so that the brain and the rest of the body are at risk, and in an attempt to keep the sugar flowing, the hormone adrenaline works to release stored sugar from the liver. Adrenaline, of course, is also the hormone released during emergencies or panic attacks. Thus, the symptoms of reactive hypoglycemia go beyond simple weakness or fatigue and very closely mimic the symptoms one experiences when frightened or nervous: rapid heartbeat, the sweats, trembling, and so forth.

Other people have what is often called fasting hypo-glycemia, which occurs not in response to eating but to having gone without food for eight or more hours. Symptoms tend to be particularly severe and can include a loss of mental acuity, seizures, and unconsciousness. Generally, fasting hypoglycemia is the result of a very serious medical condition such as liver disease or a tumor of the pancreas. If the underlying problem can be resolved, the hypo-glycemia clears up.

It should be noted that while reactive and fasting hypoglycemia are often thought of as two distinct entities, there can be overlap. "With some people, hypoglycemia can occur either soon after a meal or after many hours," comments E john Service, MD, PhD, an endocrinologist at the Mayo Clinic in Rochester, Minnesota. "There's overlap as far as the symptoms and the causes of hypoglycemia as well," Dr. Service says. "Sometimes a person with a dire medical problem can experience hypoglycemic effects soon after a meal rather than much later. And someone with so-called reactive hypoglycemia might suffer the severe symptoms usually associated with hypoglycemia that comes on during the fasting state."

However the symptoms occur and for whatever reason, hypoglycemia should never be confused with extreme hunger, which is characterized by gradually increased stomach rumbling, headache, and feelings of weakness, not drastic symptoms occurring all at once.

Making a diagnosis
One of the criteria used to confirm the presence of hypoglycemia is a blood sugar level of less than 50. Doctors used to check blood sugar by administering what is known as an oral glucose tolerance test, which measures blood sugar levels at regular intervals for several hours after a patient drinks a sugar-water solution. If blood sugar fell below 50, a diagnosis of hypoglycemia was made.

But the oral glucose tolerance test had many limitations. One was that it was frequently performed improperly. Consider that unless a patient undergoing the procedure ate extra carbohydrates for three days prior to the test, blood sugar readings could come in abnormally low; a hefty dose of sugar following several days of a relatively low-carbohydrate diet can throw off the system. That caveat was often overlooked and led to over-diagnosis.

Furthermore, even when low blood sugar was demonstrated under proper testing conditions, it wasn't always accompanied by the panic attack-like symptoms of hypoglycemia. Some people have blood sugar that can fall as low as 35 yet never experience any discomfort. Others have blood sugar in the typically normal range yet suffer hypoglycemic-type symptoms from time to time anyway. Thus, what happened in a number of cases was that patients complained of vague symptoms like tiredness and anxiety, were found to have low blood sugar on an oral glucose tolerance test, and were told they had hypoglycemia even though the test never brought on true hypoglycemic symptoms.

Yet another drawback was that the oral glucose tolerance test only demonstrated whether sugar water caused a precipitous drop in blood sugar; it never said anything about the blood sugar response to actual food. A number of people who show low blood sugar levels during an oral glucose tolerance test will show perfectly normal sugar levels after eating a regular meal that contains a mix of carbohydrates (starchy foods and/or simple sugars such as table sugar), protein, and fat. Fat, and to some extent protein, slows digestion and thereby slows the flow of sugar into the bloodstream.

To avoid over-diagnosing hypoglycemia today, physicians test blood glucose levels while a patient is experiencing symptoms within a few hours of eating a regular meal. If the symptoms and low blood sugar appear together after the meal, and if the symptoms are relieved immediately upon eating, hypoglycemia is deemed the culprit. Another type of test used to confirm the presence of hypoglycemia in some cases is the 72-hour fast, which is performed in a hospital setting under close supervision. Using these criteria, hypoglycemia is diagnosed much less frequently than it used to be.

Ironically, those most prone to hypoglycemia are people treated with drugs to control high blood sugar, or diabetes. Let's say someone with diabetes takes insulin to help remove excess sugar from the bloodstream. If the dosage of the medication is too high or is not taken at the appropriate time to handle the sugar load in the blood after food is eaten, it could end up taking too much sugar out of the bloodstream too quickly, thereby bringing on a hypoglycemic reaction.

Managing the symptoms
For the very few people who have hypoglycemia unrelated to treating diabetes and have not been diagnosed with a specific hypoglycemia-causing disease that needs to be treated directly, it's important to adopt eating habits that appear to keep blood sugar as even as possible. The recommendations:

Eat five to six small meals a day rather than three large ones to steady the release of glucose into the blood. Meals should contain not just carbohydrate but also protein and some fat. That means, practically speaking, that a mid-morning snack of half a turkey sandwich and a haft cup of milk makes a better choice for someone with hypoglycemia than a plain bagel and orange juice.
Restrict or eliminate coffee. How or why that strategy works is unclear, but some people report that giving up coffee lessens unpleasant symptoms.
Restrict or avoid alcohol. It can interfere with the liver's ability to release stored sugar.
Many people who have not been diagnosed with hypoglycemia but say eating often makes them feel poorly claim they benefit from following these recommendations. If so, fine. But, comments Jack Leahy, MD, an endocrinologist who runs the diabetes clinic at the Tufts University-affiliated New England Medical Center, it's worth keeping in mind that "in our culture, food makes a lot of people feel badly for non-physiologic reasons. Weight-conscious individuals in particular may feel guilty after eating, say, a candy bar" and therefore experience a cascade of unpleasant symptoms. "And a lot of people feel tired after meals for reasons they might believe are physiologic but which are not.

"None of this is to take away from people who feel poorly after eating," Dr. Leahy says. However, you shouldn't automatically blame feeling low or fatigued on what you've eaten. Such feelings may arise in response not to what you ate but how you feel about what you ate, or even how you feel about simply having eaten.

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