Lactose and glucose are common constituents of diet. Glucose is found in table sugar and is the chemical constituent of starch -- despite the fact that starch doesn't taste sweet. Lactose is milk sugar, and is found in milk and many other dairy foods. There are different reasons for dietary intolerances to glucose and lactose.
Significance
Glucose and lactose can, in individuals without digestive difficulty or underlying disease processes, provide for cellular energy needs. Lactose, explain Doctors Reginald Garrett and Charles Grisham in their book "Biochemistry," is actually made up of two individual sugar units. One of these is glucose, while the other is a similar and closely related sugar called galactose. In the intestine, enzymes split lactose into its constituent sugar units, and they're absorbed separately.
Function
Body cells need nutritional molecules for energy. Sugars, including glucose and galactose, are among the most important nutritional molecules. Of this, glucose is the most ubiquitous in nature, and many body cells use it preferentially. There's technically no such thing as a glucose "intolerance" -- a body incapable of absorbing or processing glucose would have limited survival capacity. The disease process diabetes, however, makes it impossible for cells to take up glucose from the bloodstream, leading to a variety of problems, including seizures and coma.
Considerations
Lactose intolerance is a relatively common dietary concern, explains Dr. Lauralee Sherwood in her book "Human Physiology." This intolerance stems from an absence of the enzyme lactase, which cleaves lactose into glucose and galactose in the gut. Since the body can't absorb lactose until it has been split, individuals missing the lactase enzyme can't digest and absorb lactose. As such, it passes undigested into the gut, and there it's digested by intestinal bacteria.
Potential
Lactose intolerance and diabetes lead to the potential for complications. Lactose intolerant individuals, if they consume milk or other lactose-containing foods, experience severe digestive discomfort, bloating and cramping. Type 1 diabetics, if they consume glucose, require a shot of the hormone insulin to help cells take up glucose. In the absence of glucose, diabetics can become very hyperglycemic, or have very high blood sugar, which can be an emergency, notes Sherwood.
Expert Insight
While individuals with lactose intolerance can't digest lactose, they can enjoy dairy if the lactose is pre-digested into its constituent sugars, glucose and galactose. Many bacteria possess the enzyme lactase, note Doctors Mary Campbell and Shawn Farrell in their book "Biochemistry." As such, bacterially processed dairy, including yogurt, often doesn't lead to symptoms in individuals with lactose intolerance because there is no longer any lactose in the dairy to cause intestinal discomfort.
References
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
