Lactose is a sugar that exists exclusively in milk and dairy products. Galactose, one of the sugars in lactose, is essential for infants to develop neuronal and nervous tissue. However, the body naturally produces galactose; therefore, dietary supplementation is unnecessary. Although it does not taste sweet like other sugars, such as sucrose and fructose, the body metabolizes and utilizes lactose in the same way.
Digestion
The only carbohydrate that mammals produce, lactose is a sugar comprised of glucose and galactose. Mammary glands manufacture lactose by first converting glucose molecules into galactose molecules, then joining them with unconverted glucose molecules. The body metabolizes lactose by converting galactose into glucose using lactase, an enzyme produced in the small intestine. Although lactose contains both glucose and galactose, the two saccharides compete for absorption, resulting in small amounts of glucose that actually enters the bloodstream.
Galactosemia
Galactosemia is an incapacity to metabolize galactose, one of the simple sugars that comprise lactose. It is inherited and has three forms: galactose-1 phosphate uridyl transferase deficiency, galactose-6-phosphate epimerase deficiency and galactose kinase deficiency. Due to this condition, galactose builds up in the system after ingesting lactose, causing harm to the brain, eyes, liver and kidneys. Galactosemia is apparent from infancy, evidenced by convulsions, lethargy, poor growth, vomiting, jaundice, lack of appetite or aversion to milk and irritability. These symptoms may also be indicative of a serious E. coli infection.
Intolerance
Lactose intolerance is a condition resulting from an inability to metabolize lactose, usually due to an absence or deficiency of lactase in the small intestine. The condition usually is not serious or dangerous, but may cause digestive discomfort, such as diarrhea, bloating and gas. In fact, many people have low lactase, but do not experience symptoms, according to MayoClinic.com. Subsequently, lactose intolerance is specifically a deficient or absent lactase with accompanying symptoms.
Interactions
Lactose is not ethanol soluble and therefore, crystallizes after adding ethanol to whey. In this way, the lactose separates from the diary product. Lactose also plays a role in milk fermentation; when left standing at room temperature, bacteria like lactobactilli in milk digest lactose and produce lactic acid. This causes water to separate and the milk to coagulate. Other acids, such as citric acid from fruits like lemons and pineapples, will cause the same effect in milk.
References
- "Introduction to Organic Laboratory Techniques: A Small Scale Approach"; Donald L. Pavia; 2005
- "The New Glucose Revolution Low GI Eating Made Easy: The Beginner's Guide to Eating with the Glycemic Index"; Jennie Brand-Miller, Kaye Foster-Powell and Philippa Sandall; 2005
- MedlinePlus: Lactose Intolerance
- MedlinePlus: Galactosemia
- MayoClinic.com: Lactose Intolerance
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