What Causes Lactose Intolerance?
Lactose intolerance is the inability to break down a type of
natural sugar called lactose. Lactose
is commonly found in dairy products, such as milk and yogurt. A person becomes
lactose intolerant when his or her small intestine stops making enough of the
enzyme lactase to digest and break
down the lactose. When this happens, the undigested lactose moves into the
large intestine. The bacteria that are normally present in the large intestine
interact with the undigested lactose and cause symptoms such as bloating, gas,
and diarrhea. The condition may also be called lactase deficiency.
Lactose intolerance is very common in adults, particularly those
with Asian, African, Native American, or Mediterranean ancestry. According to Mayo Clinic, nearly
30 million American people over the age of 20 are lactose intolerant. The
condition isn’t serious but may be unpleasant.
Lactose intolerance usually causes gastrointestinal
symptoms, such as gas, bloating, and diarrhea, about 30 minutes to two hours
after ingesting milk or other dairy products containing lactose. People who are
lactose intolerant may need to avoid eating these products or take medicines
containing the lactase enzyme before doing so.
Types of Lactose
There are three main types of lactose intolerance, each
with different causes:
Lactose Intolerance (Normal Result of Aging)
This is the most common type of lactose intolerance.
Most people are born with enough lactase. Babies need the
enzyme in order to digest their mother’s milk. The amount of lactase a person
makes may decrease over time. This is because as people age, they eat a more
diverse diet and rely less on milk.
The decline in lactase is gradual. This type of lactose
intolerance is more common in people with Asian, African, Native American, or
Lactose Intolerance (Due to Illness or Injury)
Intestinal diseases such as celiac disease and inflammatory bowel
disease or a surgery or injury to your small intestine can also cause
lactose intolerance. Lactase levels may be restored if the underlying disorder
or Developmental Lactose Intolerance (Being Born with the Condition)
In very rare cases, lactose intolerance is inherited. A
defective gene can be passed from the parents to a child, resulting in the
complete absence of lactase in the child. This is referred to as congenital
In this case, your baby will be intolerant of breast milk.
They will have diarrhea as soon as human milk or a formula containing lactose
is introduced. If it’s not recognized and treated early on, the condition can
be life-threatening. The diarrhea can cause dehydration and electrolyte loss.
The condition can be treated easily by giving the baby a lactose-free infant
formula instead of milk.
Occasionally, a type of lactose intolerance called developmental
lactose intolerance occurs when a baby is born prematurely. This is because
lactase production in the baby begins later in the pregnancy, after at least 34
What Are the
Symptoms of Lactose Intolerance?
The symptoms of lactose intolerance typically occur
between 30 minutes and two hours after eating or drinking a milk or dairy
product, and may include:
The symptoms can range from mild to severe. The severity
depends on how much lactose was consumed and how much lactase the person has
How Is Lactose
If you’re experiencing cramps, bloating, and diarrhea
after drinking milk or eating and drinking milk products, your doctor may want
to test you for lactose intolerance. Confirmatory tests measure lactase
activity in the body. These tests include:
This blood test measures your body’s reaction to a liquid
that contains high lactose levels.
This test measures the amount of hydrogen in your breath after
consuming a drink high in lactose. If your body is unable to digest the
lactose, the bacteria in your intestine will break it down instead. The process
by which bacteria break down sugars like lactose is called fermentation. Fermentation
releases hydrogen and other gases. These gases are absorbed and eventually
exhaled. If you aren’t fully digesting lactose, the hydrogen breath test will
show a higher than normal amount of hydrogen in your breath.
This test is more often done in infants and children. It
measures the amount of lactic acid in a stool sample. Lactic acid accumulates
when bacteria in the intestine ferment the undigested lactose.
How Is Lactose
There’s currently no way to make your body produce more
lactose. Treatment for lactose intolerance involves decreasing or completely
removing milk products from the diet.
Many people who are lactose intolerant can still have up
to 1/2 cup of milk without experiencing any symptoms. Lactose-free milk
products can also be found at most supermarkets. And not all dairy products
contain a lot of lactose. You may still be able to eat some hard cheeses, such
as cheddar, Swiss, and Parmesan, or cultured milk products like yogurt. Low-fat
or nonfat milk products typically have less lactose as well.
An over-the-counter lactase enzyme is available in
capsule, pill, drops, or chewable form to take before consuming dairy products.
The drops can also be added to a carton of milk.
People who are lactose intolerant and not consuming milk
or dairy products may become deficient in calcium, vitamin D, riboflavin, and
protein. Taking calcium supplements or eating foods that are either naturally
high in calcium or are calcium-fortified is recommended.
The Long Term:
Adjusting to a Lactose-Free Diet and Lifestyle
Symptoms will go away if milk and milk products are
removed from the diet. Learn to read food labels carefully to detect
ingredients that may contain lactose. Aside from milk and cream, look out for
ingredients derived from milk, such as:
- whey or whey
- casein or
- dry milk solids or
Many foods that you would not expect to contain milk may
actually contain milk and lactose. Examples include:
- salad dressings
- frozen waffles
- non-kosher lunch
- dry breakfast
- baking mixes
- many instant soups
Milk and milk products are often added to processed foods.
Even some nondairy creamers and medications may contain milk products and
Lactose intolerance cannot be prevented. The symptoms of
lactose intolerance can be prevented by eating less dairy. Drinking low-fat or
fat-free milk may also result in fewer symptoms. Try dairy milk alternatives
such as almond, flax, soy, or rice milk. Milk products with the lactose removed
are also available.