Genetic Traits Lactose Intolerance

Lactose intolerance stats are surprising to many. An estimated 30 to 50 million Americans are lactose intolerant, but certain ethnic groups are more susceptible than others. For instance, over 90 percent of Asian Americans, over 80 percent of American Indians, up to 80 percent of African Americans, and 53 percent of Mexican Americans are lactose intolerant. Babies born prematurely, before 32 weeks of gestation, may also have a lactase deficiency because lactase increases during the third trimester. This information has led experts toward researching the genetic link to lactose intolerance.

About Lactose Intolerance

If you are lactose intolerant, youre unable to digest the milk sugar, called lactose, in dairy products. Caused by a deficiency of the lactase enzyme, which is produced in the lining of the small intestine, lactose intolerance symptoms include:

  • abdominal cramps
  • bloating
  • diarrhea
  • gas
  • nausea.

The symptoms may be anywhere from mild to severe (depending on your age, ethnicity, and rate of digestion) and usually begin somewhere between 30 minutes to two hours after ingesting the lactose.

The Biology of Lactose Intolerance

When the cells lining your small intestine produce enough lactase, the enzyme can break lactose down into glucose and galactose simple sugars, which are then absorbed into your bloodstream. If, however, you are lactase-deficient, the lactose travels to the colon and interacts with bacteria in your intestine, causing gas, bloating, and other unpleasant symptoms. There are three main causes of lactose intolerance.

  • Primary: As you age, lactase production decreases and may cause lactose intolerance.
  • Secondary: Injury to, or disease of, the small intestine can affect lactase production.
  • Congential: Some people may inherit a likelihood of developing lactose intolerance.

The Genetics of Lactose Intolerance Risk

There is, in fact, a gene that controls lactase production. Interestingly, researchers have been able to link the lactase persistence gene expression to cultures with a long history of dairy farming, such as Northern Europeans, the Tutsis of central Africa, and some peoples in India. It seems these groups adapted over the past 10,000 years to be able to digest milk sugar, whereas the original gene expression was to stop or reduce lactase production around age two.

Interpreting Your Genetic Test Results

If you inherit the lactase persistence allele from each parent, then you will most likely produce significant lactase into adulthood. Even if you only inherit one of these dominant lactase persistence alleles, and the other is a lactase restriction allele, you will still likely produce lactase beyond childhood. If, however, you inherit both lactase restriction alleles, you are more likely to become lactose intolerant at some point in your lifetime.

Preventing and Treating Lactose Intolerance

If you inherited lactose intolerance from your parents, you cant do anything to increase your bodys lactase production. However, you can manage your symptoms with lifestyle and diet modifications. Infants and very young children with lactose intolerance need to avoid lactose until their bodies can more readily digest it. Older children and adults can usually handle some lactose; you just need to figure out how much and what types of foods are okay. Here are some tips to minimize your lactose intolerance symptoms:

  • Stick with small servings. Lactose is less likely to cause problems in small doses.
  • Drink milk with meals to slow your digestion.
  • Try different kinds of dairy products. You may be able to tolerate some cheeses and yogurts more than others.
  • Look for lactose-free and lactose-reduced products.
  • Take a lactase enzyme tablet with food to help break down lactose.
  • Use probiotics to help with digestion.

Frequently Asked Questions About Lactose Intolerance

Q: How do I know if Im lactose intolerant?

A: Besides evaluating your gastrointestinal symptoms, you may want to look into one of the following diagnostic tests:

  • Lactose Tolerance Test: Blood draws following consumption of a lactose-containing liquid determine your bodys ability to digest lactose.
  • Hydrogen Breath Test: Breath analysis after consuming lactose beverage measures the amount of exhaled hydrogen; increased hydrogen indicates impaired lactose digestion.
  • Stool Acidity Test: For infants and children, this measures acidity in the stool; increased acidity points to undigested and unabsorbed lactose.
  • DNA Testing: DNA test determines genetic susceptibility to lactose intolerance.

Q: What foods contain lactose?

A: Lactose comes exclusively from dairy products, but is also used as an additive in some breads, cereals, margarine, non-Kosher lunch meats, salad dressings, baking mixes, snack foods, and medicines. Check ingredient lists for lactose and milk products.

Q: What are the long-term effects of lactose intolerance?

A: In general, lactose intolerance does not adversely affect your health. The biggest risk is calcium and/or vitamin D deficiency, so make sure to get plenty of these through diet and supplements.

Recent News on Lactose Intolerance

A 2005 Cornell University study confirmed that people descended from dairy herd- raising ancestors have adapted to be able to digest milk products. In 2005, researchers analyzed data from 270 indigenous Eurasian and African populations in 39 different countries and found great ranges in lactose intolerance, from 2 percent in Denmark to 100 percent in Zambia. Cultures that were able to safely and economically raise dairy herds developed and then passed on the ability to produce lactase throughout life.

Resources

Food Reactions. (n.d.). Prevalence of lactose intolerance. Retrieved June 24, 2009, from the Food Reactions Web site: http://www.foodreactions.org/intolerance/lactose/prevalence.html.

Lang, S. (2005). Lactose intolerance seems linked to ancestral struggles with harsh climate and cattle diseases, Cornell study finds. Retrieved June 28, 2009, from the Cornell News Service Web site: http://www.news.cornell.edu/stories/June05/lactase.herding.ssl.html.

National Digestive Diseases Information Clearinghouse. (n.d.). Lactose intolerance. Retrieved June 24, 2009, from the National Institute of Diabetes and Digestive and Kidney Diseases Web site: http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/#cause.

Mayo Foundation for Medical Education and Research. (n.d.) Lactose intolerance. Retrieved June 24, 2009, from the MayoClinic Web site: http://mayoclinic.com/health/lactose-intolerance/DS00530/DSECTION=causes.

Randerson, J. (2002). Genetic basis for lactose intolerance revealed. Retrieved June 24, 2009, from the NewScientist Web site: http://www.newscientist.com/article/dn1787-genetic-basis-for-lactose-intolerance-revealed.html.

The Cambridge World History of Food. (n.d.). Lactose intolerance. Retrieved June 25, 2009, from the Cambridge World History of Food Web site: http://www.cambridge.org/us/books/kiple/lactose.htm.

Upton, J. (2007). A simple gene test for lactose intolerance/adult hypolactasia. Retrieved June 28, 2009, fro m The New Zealand Medical Journal Web site: http://www.nzma.org.nz/journal/120-1265/2817/.