Download Lactose Intolerance

Lactose Intolerance
Before You Read: Answer the following questions in your composition book. If you are unsure of the answer, make your best guess.
True/False
1) The inability to consume dairy products (lactose intolerance) was once normal, and our current ability to digest dairy today
is the result of a change in our DNA.
2) Based on diet alone, adults need to be able to digest more milk than babies.
3) When we eat food, the food’s individual polymers are broken down by enzymes into monomers that can be absorbed by
the intestine.
What is it?
Milk and other dairy products contain a special disaccharide (polymer) called lactose (monomers glucose + galactose). Normally,
lactose is broken down into its monomer components during digestion and absorbed into the bloodstream. However, some people
cannot breakdown (digest) lactose. “When undigested lactose reaches the large intestine, it attracts fluids and is attacked by gasproducing bacteria, resulting in one or more symptoms of lactose intolerance: abdominal bloating… fatty stools and diarrhea (Brody).
Individuals who experience these symptoms after consuming diary products are diagnosed as “lactose intolerant” because they cannot
digest lactose. So, what happens during digestion that allows some to digest lactose while others cannot?
The Problem
Lactose is broken into its monomer components by an enzyme called lactase. The polymers are broken into monomers during
digestion and the monomers are then absorbed in the small intestine. Lactose intolerance is caused by missing or low levels of lactase
enzyme in the small intestine where it is produced. Millions of people have been diagnosed and as a result many avoid milk and other
dairy products. Since dairy products are a leading source of essential nutrients like calcium and vitamin D, many lactose intolerant
individuals also suffer from diseases caused by nutrient deficiency, like osteoporosis (weak bones).
The Cause
In about 30 percent of people worldwide, a genetic mutation (change in DNA) arose long ago that resulted in lifelong over-production
of lactase. When an individual with this mutated gene has children with someone who lacks the mutated gene, half of their children
are likely to develop lactose intolerance as adults. To restate, lactose intolerance was once normal in nearly all people, but a genetic
mutation caused lactase over-production. When these individuals passed their genes to their children, half were lactose intolerant
(normal gene), and half were not (mutated gene). As time continued, the prevalence of the mutated gene continued to grow with each
generation, and as a result, most of us today digest lactose because the mutated gene prevailed over the original. Currently, about 1 in
4 American adults cannot properly digest and absorb lactose.
Living with Lactose Intolerance
Babies produce very large amounts of lactase since their diet is primarily milk. When we grow older (past 2 years) our lactase
production decreases because our diet expands to include many other foods besides milk.
Lactose intolerance is dose-dependent. This means, while you may be able to consume half a glass of milk on an empty
stomach without developing symptoms, two glasses could make you very uncomfortable. Milk consumed at the end of a meal or along
with other foods, especially fiber-rich foods like a whole-grain cereal, is likely to be more easily digested.
The type of dairy product makes a difference as well. Hard cheeses contain little or no lactose, but buttermilk has as much
lactose as milk. Ice cream and cottage cheese have only slightly less lactose than milk because milk is often one of the main
ingredients.
Yogurt, too, is fairly rich in lactose but with an important difference. The bacterial cultures used to produce yogurt digest
some of the lactose in the process. And if the yogurt is not reheated after it is produced, these bacteria will stay alive and assist your
digestive process. Yogurt brands certified as containing "live and active cultures" by the National Yogurt Association will say soon
the label. Some that say they contain active cultures may have been reheated after the yogurt was made. Frozen yogurt, on the other
hand, is re-pasteurized (killing the bacteria) and may cause symptoms when consumed by those with a severe lactose intolerance.
Possible Solutions
Many have turned to new and more costly digestive aids, including lactose-reduced milk, cottage cheese and ice cream, enzyme drops
that can be added to liquid dairy products at home and enzyme tablets that can be taken when dairy and other lactose-containing
products are consumed.
Furthermore, new studies suggest that lactose intolerance is not an all-or-nothing phenomenon. Rather, many people with
lactose deficiency can continue to consume moderate amounts of milk and other dairy products without experiencing symptoms and
without having to use or take any special products. Furthermore, researchers have found that if people with the enzyme deficiency
regularly consume moderate amounts of lactose, their bodies adapt and they experience none of the classic symptoms.
The studies also indicate that a significant percentage of people who think they are lactose intolerant are really not. While
they do develop symptoms similar to those caused by the enzyme deficiency, the reason for their symptoms is not a lack of lactase.
Answer the following in your composition book.
1. What is the role of lactase in milk digestion?
2. How can lactose intolerance be diagnosed?
3. Based on what you know about babies’ diets, do babies produce more, or less lactase than their parents? Explain.
4. Why do most yogurts not make lactose intolerant individuals sick?
5. How does your genetic make up influence your chance of being lactose intolerant?