Most people in the world can't drink milk without having intestinal upset. The enzyme, lactase, which breaks down milk sugar in infancy fades away in those with lactose intolerance. Almost everyone in the world is born with the lactase enzyme. Humans couldn't have survived without having babies who could drink breastmilk.

But for 60% or more of the world's population, including many of those whose families came from many parts of Africa, Asia, and the Mediterranean, lactase isn't produced and active after 7 or 8 years of age. They have permanent or primary lactose intolerance.

Because the enzyme sits on the tips of the intestinal surface, lactase can also be temporarily damaged if there's a virus or bacteria that disrupts the intestinal surface. The same is true for those with celiac disease where gluten has injured the surface. But after the infection is over or the gluten is removed, the enzyme usually returns within 4 weeks or so and lactose can be digested again.

The Symptoms

  • Bloating
  • Flatulence (gas passed from below)
  • Diarrhea
  • Abdominal pain

The symptoms are created when milk sugar can't be digested and absorbed, so the intestinal bacteria break lactose into water and different gases. The gases create a bloating sensation until they are passed, and the extra water causes diarrhea. And together, the gas and diarrhea cause the abdominal pain, often at the area around the belly button or to the left and below. How severe the symptoms are depends on the amount of lactose consumed and the severity of the disorder (it can vary greatly). If vomiting or a rash are present, lactose intolerance is NOT the cause. Milk allergy or other disorders need to be considered.

Nutritional Aspects

Milk and milk products are important sources for protein, calcium and phosphorus Additionally, cow's milk is supplemented with Vitamin D--a nutrient that most of us don't get in the quantity we need. When someone has lactose intolerance, and avoids dairy, those sources need to be replaced. Other beverages, often called milks, are available as are other lactose-free dairy substitutes . Additionally, a replacement enzyme, Lactaid, can be taken along with dairy products, which will lessen or eliminate the symptoms so that kids with lactose intolerance can once again eat normal ice cream and pizza.

The difference between milk allergy and lactose intolerance, is that milk allergy is a reaction to a milk protein (most likely the casein but it could be one of the whey proteins), while lactose intolerance is a usually milder reaction to the sugar in milk.

As a result, with milk allergy, you have to read labels and see whether they list anything that could contain milk protein.  These include:

Some infants and children continue to have diarrhea after an intestinal infection (gastroenteritis).  Their fever breaks and their vomiting subsides, but the diarrhea continues for days or even weeks.

You may not know it, but most people in the world can't drink milk--not without suffering the consequences of diarrhea, discomfort or gas. They have lactose intolerance. It's hereditary. So at least one of their parents has the same problem. They may not recognize the problem, because over the years they've learned to shy away from milk products. They don't like ice cream or milk, because instead of feeling good when they lick their ice cream cones, they feel bloated and uncomfortable within a few hours.