Serendip is an independent site partnering with faculty at multiple colleges and universities around the world. Happy exploring!

Lactose Intolerance

Annabella Wood's picture

Do you feel sick after ingesting milk products? Do you have to stay away from foods that
contain milk or cheese? If so, you are possibly lactose intolerant. You might also be
allergic to dairy. The two conditions are not the same, though they share one effect on
people’s lives; staying away from dairy foods. We will not explore dairy allergies in this

Here we are exploring lactose intolerance. What is lactose intolerance? Lactose
intolerance is a condition brought on by a lack of the digestive enzyme lactase, whose job
it is to break up the lactose molecule during digestion. If you don’t have enough lactase
to break up the lactose in your digestion system, lactose will remain inside the intestine.
It can not pass through the intestinal membrane wall to be absorbed into the blood stream.
When the lactose is sitting in your intestine, digestive bacteria will do its best to
metabolize the lactose. In doing so, the bacteria put off large amounts of gas, resulting in
your experience of bloating, flatulence and diarrhea, all of which can be quite painful. (1)

The lactose molecule is a macromolecule made up of two saccarides; galactose and
glucose. (2) These molecules are made up of OH, CH2 and O atoms and molecules.
When the digestive enzyme lactase is present, it will break apart the lactose into its
constituents; galactose and glucose. These simpler sugars can easily pass through the
intestinal membrane wall and be absorbed into the blood.

A deficiency in lactase can be caused by a number of factors. Everyone slows lactase
production around the age of 2. Some stop making it altogether as small children, while
others continue to make it well into adulthood. (3) What are the determining factors with
regard to lactase production?

It could be hereditary. You may have inherited limited lactase production from your
parents. If only one parent is carrying a limited lactase production gene, even if they
themselves produce lactase into adulthood, they could pass limited lactase production on
to their children. For this reason, lactose intolerance seems to run higher in different
ethnicities than in others. While only about 15% of North American whites are lactose
intolerant, up to 95% of African blacks are intolerant. In fact, those who can digest large
quantities of lactose are in the worldwide minority.

Additionally, lactose intolerance rises with age. Since the body tapers off lactase
production with time, as people get older, their ability to break down lactose decreases.
So even if you consume a lot of dairy now, you may not be able to in a couple of years.

But there are other causes for lactase deficiency. Premature babies are prone to deficient
lactase production. If your intestines suffer an injury, you may lose lactase production.
Certain diseases can reduce lactase production, diseases such as celiac disease,
inflammatory bowel disease, and Crohn’s disease. (5)
We’ve already discussed the immediate symptoms of lactose intolerance. But there are
also possible links to long term problems that could be associated with this condition.
Namely, osteoporosis. It is a condition in which the bones become less dense, making
them thinner, more brittle and therefore more prone to breaking with longer healing
times. It is brought on by a deficiency in calcium in the bones. Osteoporosis is generally
thought of as a post menopausal women’s disease. But among those afflicted with
osteoporosis, 68% are women and 32% men. So this is not only a women’s disease. (6)

Though osteoporosis can be caused by the hormonal changes in post menopausal women,
it can also be brought on by many other factors, one of which may be lactose intolerance.
Since lactose intolerant people are less likely to drink milk, a good source of calcium, we
would expect that they are more likely to develop osteoporosis. However, research has
been inconclusive on this question. Though some studies do suggest a connection, other
studies do not. (6) So though this question is still unanswered, it is good common sense to
be certain that you take in calcium in other ways if you are lactose intolerant.

Though there is no “cure” for lactose intolerance, there are many things you can do to
alleviate its effects. The first thing most people do once they find they are lactose
intolerant is they stay away from dairy. But there are other solutions. If you really like
dairy, you can add lactase to your food. That way, it is in your intestine at the very time
you need it to break down the lactose. You can use it in liquid or tablet form, and you just
take it with your first swallow of dairy.

Plus the food industry has been learning to make foods more edible by the lactose
intolerant. Some yogurts contain what is call “live cultures.” These live cultures actually
produce lactase enzymes right in the yogurt, so lactose intolerant people can digest the
yogurt. Lactose free milk is made by passing regular milk over lactase enzymes. The
enzymes break apart the lactose so that when you drink it, you don’t have any ill effects
from lactose. (1)

Lactose intolerance is not an all or nothing condition. There are degrees of intolerance.
Some people can actually increase their tolerance for lactose by introducing it into their
bodies in measured quantities, increasing those quantities over time. But this method is
under debate as to whether the person is actually becoming more able to digest lactose or
just becoming more accustomed to its symptoms. Many people who can not digest milk,
can digest certain aged cheeses or other food products with reduced levels of lactose.
Since lactose digestion is a direct result of the presence of the lactase enzyme, by simply
not taking in more lactose than you have lactase you can avoid the symptoms of lactose
intolerance. By paying attention to what you eat, how much of it you eat, and how you
feel afterward you can figure out how much dairy you can ingest without negative

What are the chances you will become lactose intolerant during your lifetime? Pretty
good. Consider yourself lucky if you enjoy consuming dairy without consequence.
You’re already in the minority. As you get older, the minority becomes smaller. Should
you still be lactose tolerant as an elderly person, you have definitely beaten the
odds…buy a lottery ticket. You might just win that game too.

1) Wikipedia definition of lactose intolerance

2) Wikipedia picture of lactose

3) Article about lactose intolerance

4) How do you get lactose intolerance

5) Article linking osteoporosis with lactose intolerance.

6) Osteoporosis and lactose intolerance


Anonymous's picture

Raw cow's milk contains

Raw cow's milk contains lactase, the process of pasteurization is what eliminates it.
I am allergic to pateurizewd dairy and have NO PROBLEM with raw dairy.
Learn more about raw milk and how to obtain it
is a good resource.

Anonymous's picture


I am lactose intolerant and I have been for almost a year now. I use Lactaid milk and it tastes fine. I also recommend lactaid ice-cream. It tastes like regular ice-cream. :)

Tom's picture

Rice and Easy

I am lactose intolerant as well. I use Rice and Easy. It's a milk made out of whole grain rice which has added calcium and Vitamin D. It tastes good and it's healthy, I am pretty happy with it.

Anonymous's picture


well i am lactose intolerant and i just found it out. and its hard but the choclat soycream tastes like regular and it didnt bother me

Biology Student 2006's picture

the vegan strikes again

Isn't it curious that humans are the only mammals that drink the milk of other animals? Cow's milk is intended to feed calves, which can gain up to 60 pounds in their first few months of life. Is milk then nutritionally beneficial for human adults?
Serendip Visitor's picture

I believe that humans only

I believe that humans only drink milk as a source of calcium, so technically, it isn't.