The Many Names for Lactose Intolerance      Here's how much the world has advanced over the past 20 years. If you say the words "Lactose Intolerance" most everybody will know what you mean. But the world is never that simple. Different people use the words Lactose Intolerance in slightly different ways. And doctors almost always use other words entirely when they're talking about what we call Lactose Intolerance. So here's a listing of almost all the world's names for Lactose Intolerance (LI) and its opposite, along with explanations of exactly what people might mean when they use the words. Lactose Intolerance (LI)   This is the common, generic, name for the condition, but it gets both misused and overused.   Technically speaking, LI only refers to the appearance of symptoms (usually gas, bloating, cramps, or diarrhea) from whatever cause after the ingestion of lactose-containing dairy products. You do not necessarily have to test positively as being a lactose maldigester to have Lactose Intolerance.   Being LI usually implies that you have lost some of your ability to manufacture the enzyme, lactase, that digests lactose, but it may occur even if tests show that you have a sufficient lactase supply.   Even so, in popular usage -- and in much medical usage -- LI is used interchangeably to mean either the symptoms from dairy products or the loss of lactase that is the usual cause of those symptoms.   And I use Lactose Intolerance almost exclusively throughout my web site in just that interchangeable way.   Lactose Maldigestion Lactose Malabsorption Low Lactose Digestion Capacity   This is the condition we all think we have. All it means, however, is the inability to digest molecules of lactose.   It could be caused by the natural decline of production of the lactose-digesting enzyme lactase, or by reduced lactase activity caused by damage to the intestines, or by other intestinal ailments or medications that prevent the intestines from working properly.   The term is a formal medical term that should properly be used only as a medical diagnosis following testing that proves that the condition exists.   You'll notice that nothing is said in this definition about having any symptoms from this inability to digest lactose. Many people test as being lactose maldigesters, but never show any symptoms.     Milk Intolerance due to Lactose   Nitpickers may sometimes use this term to refer to symptoms experienced after eating or drinking milk or dairy products in food. That's because not all milk intolerance is due to lactose, even in people who have been diagnosed as LI. Odd as it may seem, they may be no relationship at all between symptoms and low lactase levels in any given person.     Lactase Deficiency Lactase Nonpersistence   You are lactase deficient if you have less than the "normal" supply of lactase. As you may expect from that definition, this term gets used pretty loosely to mean either lactose maldigestion or lactose intolerance or both.     Hypolactasia   Technically, a very low state of lactase activity in the small intestine.   In practice, this is the European term that is the equivalent to lactase deficiency, used to mean either lactose maldigestion or lactose intolerance or both.     Alactasia   A state of total lack of lactase activity in the small intestine. This condition is rare naturally. It is usually the result of ilness, trauma to the small intestinal, or the removal of parts or all of the small intestine.   It is sometimes also technically referred to as lactase deficiency, which is too bad because that is very different from how the term is normally used.     Primary Lactose Intolerance (PLI) Adult-Onset LI Late Onset LI Delayed-Onset LI   This is how powerful popular usage can get.   Even though the medical community uses LI differently from the rest of the population, they still use LI in the usual, common, way as part of a larger term.   PLI has nothing to do with symptoms. It refers to the natural decline in lactase production that occurs in roughly 70% of the world's population.   But if that decline starts in children in most of the world, then why is it called adult-onset or late-onset or delayed-onset?   Simply because the medical researchers of the world, until very recently, were white northern Europeans. And whenever they saw PLI, they saw it in adults.   It wasn't until the 1970s that most doctors began to become aware that in many, if not most, Native American, African, and Asian populations, lactase begins to decline at about the age of weaning.   The fact that many doctors even today seem to have no idea that this is true would be just an embarrassment for the medical community if it didn't have real effects in the real world of the United States.   Since immigration to the U.S. is increasing precisely from those areas of the world in which PLI starts in children, the Lactose Intolerance of many children is not being recognized.     Secondary Lactose Intolerance (SLI)   Lactase is made in a delicate and vulnerable part of the small intestine. If the intestine is damaged, so is the body's ability to manufacture lactase. This condition is called Secondary Lactose Intolerance to distinguish it from the natural gradual loss of lactase ability.   The list of conditions that can bring on SLI is a long one. Many diseases can, from a simple gastrointestinal flu (very common in infants) to deadly illness like cancer. Operations to the small intestine, especially those that remove portions of it, are also a leading cause. But some drugs can produce it, and so can long-term trauma to the body as in alcoholism.   Whether SLI is temporary or permanent depends on the cause. Often the condition goes away after the intestines have had time to heal. Infants may become temporarily intolerant several times in just a couple of years.   On the other hand, if you are an adult who was beginning to lose your lactase-producing ability naturally, even a slight shock to the intestine may cause a permanent inability.     Congenital Lactose Intolerance (CLI)   A very, very, very few babies are born without the ability to manufacture lactase at all. Since this occurs from birth, it is referred to as Congenital LI. It is extremely rare, and only a few cases are known worldwide. Until recently, any baby with this affliction was doomed to a quick death. Today, however, the diagnosis should be made quite quickly. CLI babies can be put on a non-dairy formula and thrive as well as any others. However, this must avoid all dairy products for the rest of their lives.