What is Lactose Intolerance?

What is Lactose Intolerance?

Lactose intolerance is the inability to digest significant amounts of lactose (e.g. 8 fl oz of milk), the major sugar found in milk and milk products.

Lactose intolerance is caused in part by a shortage of lactase, an enzyme produced by the cells that line the small intestine. Lactase breaks lactose down into the simple forms of sugar, glucose and galactose, so they can be absorbed and used by the body.

Infants have the highest levels of lactase, which helps them digest their mother’s milk.

In about 75% of the world’s population, a genetic trait causes lactase levels to start irreversibly decreasing after weaning. By adulthood, most lactase activity is lost.

Although the decline in lactase activity affects the majority of the population, not everyone has symptoms of lactose intolerance after consuming normal amounts of lactose.

Whether or not people develop symptoms appears to be linked to the ability of a certain type of beneficial bacteria, called lactic acid bacteria, to break down lactose. Some people may have more lactic acid bacteria in their intestines than others, so they don’t develop symptoms. People who do are said to have lactose intolerance.

Symptoms of Lactose Intolerance

Symptoms of lactose intolerance include:

  • Gas
  • Cramping
  • Abdominal Pain
  • Nausea
  • Bloating
  • Diarrhea

Lactose left undigested in the intestines can result in diarrhea, because of the excessive amounts of water that are drawn into the intestines by lactose. Hydrogen is produced, causing gas and bloating.

What Natural Remedies Do People Use?

Acidophilus is one of many types of lactic acid bacteria. Lactic acid bacteria in the intestines breaks lactose down into short-chain fatty acids and other substances that can be absorbed by the colon.

Lactic acid bacteria are available as dietary supplements. They are usually found as capsules, tablets, or powders in the refrigerated section of health food stores. They are also available at some drug stores, grocery stores, and online.

There are many different types of lactic acid bacteria. The ones used most often for lactose intolerance include:

  • Lactobacillus acidophilus
  • Lactobacillus bulgaricus
  • Streptococcus salivarius
  • Lactobacillus reuteri
  • Lactobacillus plantarum
  • Streptococcus thermophilus

The company Enzymatic Therapy makes a product called Acidophilus Pearls that doesn’t require refrigeration. It contains Lactobacillus acidophilus and Bifidiobacterium longum.

Acidophilus and the other probiotics are popular remedies to prevent and reduce symptoms of lactose intolerance. In a 2000-2002 survey of 61,587 people aged 50 to 76 years that was published in the Journal of the American Dietetic Association, acidophilus for lactose intolerance was found to be one of the top reasons people used a specific supplement for a health condition.

Despite its popularity, not all studies have found acidophilus or the other probiotics can help diminish symptoms of lactose intolerance.

In a systematic review published in 2005 in the Journal of Family Practice, researchers searched randomized controlled trials published between 1966 and 2002. Out of the 90 studies that were found, only 10 articles met their inclusion criteria.

Three out of nine studies found that probiotics reduced breath hydrogen levels and three had both positive and negative results. The breath hydrogen test is non-invasive test widely used to assess lactose intolerance, based on the finding that people with lactose intolerance exhale increased levels of hydrogen gas.

When the researchers looked at symptoms, one out of seven studies showed a significant reduction in symptoms, another had both positive and negative results, and five studies showed no benefit.

Although the results of the review appear to indicate mixed results for reducing breath hydrogen and poor results at reducing symptoms, it’s important to know that each study used a different type of lactic acid bacteria, a different concentration, and a different product. In other words, perhaps the study that found a significant reduction in symptoms used the right type of bacteria in the right amount. Further well-designed studies are needed.


Yogurt containing live active bacteria is believed to improve lactose digestion for the same reason that probiotics are thought to work.

When yogurt is consumed, bile acids disrupt the cell wall of the bacteria in yogurt. This releases the enzyme beta-galactosidase (related to lactase) into the intestines, where it can enhance lactose digestion.

Not any yogurt will do. It must contain live active bacteria.

Although yogurt is a milk product, many people with lactose intolerance do not experience symptoms after eating yogurt, even the kind that doesn’t contain live active bacteria.

Acidophilus Milk

Acidophilus milks are made by adding Lactobacillus acidophilus to cold milk. Many of the studies that have looked at acidophilus milks for lactose digestion have found no improvement. Researchers have speculated that it may be because the acidophilus products used in the studies did not contain enough acidophillus.

Lactase Supplements

Tablets containing lactase can be taken with lactose-containing foods. For many people, lactase supplements are only needed for larger quantities of lactose.

If a certain type of lactase supplement doesn’t work, it may be worthwhile to try other brands. Some people find the tablet form more effective than the chewable form.


It’s quite common for people to avoid lactose-containing foods completely, but that usually isn’t unnecessary and may contribute to calcium deficiency.

Some dietary strategies for people with lactose intolerance include:

  • Drink one cup or less of milk at a time
  • Eat milk and milk products with meals rather than alone
  • Try reduced-lactose milk
  • Try yogurt instead of milk

If You Have Lactose Intolerance

If you have just developed lactose intolerance, it’s important to consult with your doctor. Lactose intolerance can also be caused by medications or by an underlying condition that damages cells lining the intestines, such as:

  • Crohn’s disease
  • Celiac disease
  • Giardiasis
  • HIV enteropathy
  • Carcinoid Syndrome
  • Diabetic gastropathy
  • Zollinger-Ellison syndrome
  • Alcoholism
  • Iron Deficiency

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