Understanding and Preventing Violence, Volume 2: Biobehavioral Influences (1994)
Chapter: SUGAR, HYPOGLYCEMIA, AND BEHAVIOR
has become known as the "Twinkie defense," White was convicted of manslaughter rather than first-degree murder.
Is there a scientific basis for our attitudes about sugar? Before this question can be answered, the term sugar must be defined. Although many different types of sugar are found in our foods, most people use the word sugar to describe the simple carbohydrate sucrose. Sucrose, the sugar on our tables and typically used in cooking, is a disaccharide composed of the monosaccharides fructose and glucose. Sucrose is broken down into its monosaccharide components in the digestive tract and absorbed across the small intestine. After absorption, glucose and fructose are carried by the blood to the liver and other tissues. Because fructose is rapidly metabolized to glucose in the intestinal mucosa and the liver, any discussion of carbohydrate metabolism is essentially a discussion of glucose. Glucose is the metabolic fuel for most cells in the body and the primary energy source for cells in the central nervous system. The critical role of glucose in the normal functioning of the central nervous system has helped to foster the belief that sugar can affect behavior.
SUGAR, HYPOGLYCEMIA, AND BEHAVIOR
Sugar intake has been condemned as the cause of a large number of psychological problems, including alterations in mood, irritability, aggression, and violent behavior. One "physiological" explanation for sugar's adverse effects is hypoglycemia or "low blood sugar." Unfortunately, the term hypoglycemia has frequently been misused. Many doctors, as well as patients, are confused about the condition (Yager and Young, 1974; Nelson, 1985).
Clinically, hypoglycemia is defined by (1) low circulating blood glucose levels—50 milligrams per deciliter (mg/dl) or less; (2) symptoms including sweating, tremors, anxiety, headaches, weakness and hunger; and (3) amelioration of symptoms when blood glucose is restored to normal levels by food intake (Nelson, 1985; McFarland et al., 1987). Hypoglycemia can occur in diabetics after the administration of insulin. Additionally, other drugs such as antibiotics, anti-inflammatory agents, and antidepressants; insulin-secreting tumors; and renal disease can lead to hypoglycemia.
It has been suggested that sugar consumption is a causal factor in hypoglycemia. The rationale for this idea begins with the assumption that simple sugars are more rapidly digested and absorbed than complex carbohydrates and thus cause a greater increase in blood glucose levels. This rapid rise in blood glucose
levels stimulates insulin secretion, which has the effect of decreasing blood glucose levels. This regulatory effect has been called reactive or functional hypoglycemia.
There are several problems, however, with the idea that sugar intake can cause reactive hypoglycemia. First, recent studies have shown that a simple distinction cannot be made between sugars and more complex carbohydrates with respect to blood glucose and insulin responses (Crapo, 1985). Foods high in sugar can actually lead to smaller increases in blood glucose levels than foods containing complex carbohydrates. Thus, the assumption that sugar-containing foods uniformly lead to wide fluctuations in blood glucose values must be viewed with caution. Another related problem is that low blood glucose levels are not consistently associated with clinical signs of hypoglycemia. Additionally, symptoms of hypoglycemia are frequently reported in the absence of low blood glucose levels (McFarland et al., 1987).
In many cases, a diagnosis of hypoglycemia is made on the basis of symptoms without appropriate laboratory evidence (Nelson, 1985; McFarland et al., 1987). To make a diagnosis of hypoglycemia, a relationship between low blood glucose levels and the symptoms of the disease must exist. The most common ways of doing this are to conduct an oral glucose tolerance test (OGTT) or to measure blood glucose levels after a normal meal. In either case, for a diagnosis of hypoglycemia, clinical symptoms must be associated with blood glucose levels of less than 50 mg/dl. This association is rarely observed. Patients who have glucose levels lower than 50 mg/dl are infrequent (Yager and Young, 1974; Nelson, 1985; McFarland et al., 1987).
Given the relative rarity of functional hypoglycemia, why has the disease become so popular? For individuals with psychological complaints, a diagnosis of hypoglycemia may have certain benefits. First, the disease is socially acceptable. Rather than endure a "psychological" or otherwise stigmatizing condition, the patient can suffer from a respectable metabolic illness. Second, hypoglycemia gives individuals a way of easily and actively dealing with their complaints. By following certain dietary prescriptions, the patient believes that his symptoms can effectively be eliminated. In many cases, the act of attributing psychological problems to hypoglycemia and altering one's diet in response to this condition may provide some relief. Finally, hypoglycemia may be preferable to facing the possibility of a more serious condition.
