Scientists are continuously unlocking more and more secrets about the human genome, and the information we are gaining illustrates how our genes influence so much of our daily lives, from what we look like to how our bodies react to certain medications, and even what sort of foods we prefer. In the past, we have discussed how genetics have a huge effect on the development of many gastrointestinal (GI) disorders, such as celiac disease and inflammatory bowel disease, which both have genetic links. In this article, we will review some interesting things your genes dictate that can improve understanding in the GI and liver health field.


Dairy Diarrhea

While most have no problem consuming dairy products, some people can experience great intestinal distress (including diarrhea, gas, and bloating) from even relatively small amounts of these foods. The problem comes from a sugar in milk called lactose, which is broken down by an enzyme called lactase. Almost everyone is born with the ability to make lactase since lactose is a component of human breast milk. After infancy, some people lose this and become unable to digest the lactose in common dairy products; these people are lactose intolerant.

Researchers have found a genetic marker that can predict whether someone is genetically capable of producing lactase after infancy or not. This is important because some people can become lactose intolerant by not consuming lactose for a long time, but are able to slowly incorporate dairy into their diet and regain their ability to produce lactase. In other individuals, no amount of training their bodies will help them manufacture their own lactase. These people are better off taking lactase supplements before consuming dairy or consuming dairy-free alternatives. Being able to take a quick test that lets you know if you are genetically lactose intolerant or not can help you make the right choices for your physiology.


Protection from Norovirus

You’ve likely been there before, a family member, colleague, or classmate suddenly falls ill, and before you know it you and most of the people around you are suffering from vomiting, diarrhea, and abdominal pain. You may know this as its colloquially dubbed term “the stomach flu”. However, it’s actually an infection by a norovirus called viral gastroenteritis (vomiting is not a symptom of the flu). Maybe you also know someone (or perhaps you are the lucky one) who rarely seems afflicted with this disease. This person is likely resistant to the most common strain of norovirus.

Your genes control whether or not you are resistant to norovirus. Currently, we know definitively that there is one genetic marker that can show if someone is resistant to norovirus. However, there may be other genes that also make someone resistant to the virus, so not having the gene does not mean that someone cannot resist that virus.


PPI Effectiveness

Proton pump inhibitors (PPIs) are a class of medication used to treat gastroesophageal reflux disease (GERD), ulcer disease, and H. pylori infection by reducing the amount of gastric acid produced in your stomach. (See pages 20-22.) While these are typically the most effective treatment for individuals with gastric acid-related ailments, some patients find that typical doses are not very effective, or that the benefits wear off faster than they should.

Some of our genes control the manufacture of certain enzymes that metabolize and eliminate drugs and other substances from our bodies. One such gene creates enzymes that cause a rapid breakdown of PPI medications. Individuals with this genetic marker may require more frequent PPI dosing than typically prescribed, or might need to add other types of medications. This is important information to know, since a large amount of the population (35-70%, depending on ethnicity) could have this variant, and need medications adjusted accordingly.


Hepatitis C Treatment

In past newsletter articles we have told you how there are treatments available for hepatitis C that can actually cure the disease. We know that the protease inhibitors that cure hepatitis C should be combined with pegylated interferon (peginterferon) and ribavirin to be successful. We also know that some people respond very well to pegylated interferon and ribavirin, whereas other people don’t seem to respond at all.

An interesting genetic discovery shows that we may be able to tell who is likely to respond to this treatment method without having to use trial and error, but simply by looking at their genes. Certain genetic markers make individuals less likely to adequately respond to these medications. Knowing how individuals respond to medications ahead of time can greatly improve treatment for patients.


Got a Sweet Tooth?

Ever wonder why it is that some people seem to go crazy for sweet food while other people could take it or leave it? You might think it’s because of how they were raised; what they were allowed to eat as children, what foods they grew up loving, that sort of thing. However, there are actually some genetic links to whether or not you develop a sweet tooth. Researchers have found certain genetic markers that are connected to an increased consumption of sugar.

There are also genes that control how we taste bitter foods. Grapefruit and black coffee’s bitter tastes result from a variety of chemical compounds. Our genes dictate how sensitive we are to these compounds. This is why some people might detest certain bitter foods, while others wonder what all the fuss is about, and find these foods enjoyable. However, enjoying bitter foods does not necessarily mean you can’t taste the bitterness; some people simply like bitter foods.

First published in the Inside Tract® newsletter issue 188 – 2013