Reactive hypoglycemia

For some people, the classic continental breakfast of a sweet roll, orange juice, and coffee is a recipe for distress. Within a few hours after eating, they may feel light-headed, shaky, and unable to concentrate. Are such people suffering from hypoglycemia, a fancy word that simply means "low blood sugar"? Probably not, say researchers who have studied this controversial disorder over the past two decades. Far fewer people have the condition than they imagine.

In the 1970s and early 1980s, hypoglycemia was a fashionable diagnosis for patients with vague symptoms ranging from fatigue to palpitations. Some people theorized that low blood sugar accounted for such disparate social ills as juvenile delinquency and alcoholism. Doctors subjected patients who might be hypoglycemic to extensive testing, or referred them to specialists for even more costly evaluation.

David Nathan, associate professor of medicine at Harvard Medical School and director of the Diabetes Research Center at Massachusetts General Hospital, said hypoglycemia became a "wastebasket diagnosis" that physicians used to reassure patients who wanted a name for their unidentifiable and upsetting symptoms. Today medical experts agree that not only was hypoglycemia a fad label, but also that the old method of testing for low blood sugar was inaccurate and grossly inflated the number of cases.

The type of hypoglycemia once thought to be relatively common--characterized by headache, fatigue, tremulousness, sweating, palpitations, and an inability to concentrate several hours after a high-carbohydrate meal--is actually rare. Using more reliable testing methods, physicians at Massachusetts General's busy diabetes clinic, for example, see only a few patients a year who fit the criteria for this disorder, called reactive hypoglycemia because it occurs after eating. A more serious condition, called fasting hypoglycemia, occurs in response to going without food for too long. This type results from certain diseases that upset the body's ability to balance blood sugar.

These days the only people labeled as reactive hypoglycemia, the type that causes the most confusion, are those whose symptoms occur while their blood sugar is in the hypoglycemia zone--below 50 milligrams per deciliter (mg/dl)--and who improve immediately if they eat something.

Nevertheless, some clinical nutritionists believe that sudden fluctuations in blood sugar level can cause symptoms even in people whose blood glucose never dips below the 50 mg/dl threshold. Other experts disagree, saying that although these symptoms occur, sudden shifts in glucose levels are not to blame.

Testing the limits

For years the standard test for patients suspected of having low blood sugar was the oral glucose tolerance test (OGTT), which requires drinking 75 to 100 grams of glucose solution and then having blood drawn every 30 minutes for 5 hours to determine the circulating sugar level.

Although a two-hour OGTT is a highly accurate method for diagnosing diabetes, researchers have, doubted, its value for confirming hypoglycemia since the late 1970s. Some patients who test below 50 mg/dl have no symptoms of low blood sugar; others have symptoms, but their glucose levels are within the normal range (80-120) mg/dl).

In 1989, a study published in the New England Journal of Medicine determined that reactive hypoglycemia cannot be accurately diagnosed by administering an OGTT. Researchers from the University of Montreal showed that blood glucose levels are reliable only if blood samples are drawn while the patient is experiencing symptoms. This new approach to testing "put the nail in the coffin" for hypoglycemia's popularity as a diagnosis, turning up far fewer cases than physicians expected based on the OGIT or patients, reported discomfort after a meal, according to Lloyd Axelrod, senior physician and endocrinologist at Massachusetts General Hospital.

Today, patients with suspected hypoglycemia are usually told to eat the foods that typically provoke symptoms, and then to visit the doctor's office to have blood drawn and tested. Some physicians lend patients a glucometer (a device for measuring glucose) to use at home. Most of the time, blood sugar levels turn out to be in the normal range--not in the hypoglycemic zone.

Still, patients who have the classic symptoms are reacting to something, Dr. Nathan said, and it's important to find out what's going on in order to separate a real medical problem from a fad diagnosis.

Facing the facts

The brain depends on glucose for energy. Since it can't produce its own supply, it needs to have a continuous influx of glucose from the bloodstream.

In healthy people, blood sugar is kept fairly constant by the interaction of several body mechanisms that act as checks and balances to bring the system back to equilibrium. Consuming carbohydrates, whether in the form of sugary sweets or starchy potatoes, normally stimulates the pancreas to produce insulin. The surge of insulin in turn causes the circulating glucose level to fall. As the concentration of blood sugar drops, insulin returns to normal levels.

There are several reasons why this feedback system can get out of whack. In people with fasting hypoglycemia, for example, liver disorders, insulin-producing tumors (insulinomas), or adrenal gland failure can throw off the normal glucose-insulin balance. Low blood sugar can also be brought on by some drugs, such as insulin or oral medications for diabetes mellitus, or as a result of stomach surgery.

The hypoglycemia-like symptoms that some people may experience after a high-carbohydrate meal don't actually reflect a disorder in the insulin-glucose balance, but are most likely related to dietary habits, stress, or emotional factors, according to nutritionist Connie Roberts, manager of nutrition consultation and wellness programs at Boston's Brigham and Women's Hospital. Swings in blood sugar levels, rather than demonstrably low glucose, are likely to cause apparent hypoglycemia, she said. Although anecdotal evidence suggests that some people may experience symptoms above the hypoglycemic threshold, studies have not been able to demonstrate these effects.

Getting Even

Those who experience symptoms even though their blood sugar level is normal may find that changes in diet can get them back on an even keel. Skipping meals, giving in to a late afternoon craving for a chocolate bar, or indulging in caffeine or alcohol can put someone on a metabolic roller coaster, according to Roberts. Caffeine initially boosts energy by stimulating production of epinephrine, but it also increases the brain's use of glucose at the same time that it decreases cerebral blood flow, shortchanging the brain,s usual energy supply. A study published in the Annals of Internal Medicine in 1993 showed that people who consumed caffeine could develop hypoglycemic symptoms even at blood sugar levels within the low-normal range. Excessive alcohol consumption can also cause these symptoms by interfering with the liver's ability to supply glucose to the body.

Often what helps is turning feast-or-famine people into grazers. Eating several small meals throughout the day guarantees a more even level of blood sugar over time, said nutritionist Roberts. She usually recommends that people eat a diet that is moderate in lean protein (chicken and fish), and that emphasizes complex carbohydrates, (breads and cereals), rather than simple sugars (candy, sweet rolls, or fruit juice).

Dietary change may be one solution to the fatigue, mood swings, headache, and neurologic symptoms that some people chalk up to hypoglycemia. In other cases, stress or emotional problems, such as anxiety or depression, could be to blame. Because these vague symptoms can be traced to many possible causes, it is usually wise to see a doctor to determine the root of these problems.

So consider skipping the donuts and coffee on the road and grabbing a bagel and a cup of herbal tea instead. That, plus taking a few minutes to breathe deeply and unkink those neck muscles, might just do the trick.

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