What is Lactose?
Lactose is the carbohydrate sugar naturally found in milk and milk products. Lactase is the enzyme needed to break down this sugar in the digestive tract. Lactase is secreted by the cells lining the small intestine. The enzyme breaks down lactose into two simpler forms of sugar called glucose and galactose, which are then absorbed into the bloodstream.
What Does it Mean to Have Lactose Intolerance?
If you have lactose intolerance, it means that you an inability to digest lactose in milk, or that you have an insufficient ability to digest it. Specifically, lactose intolerance is caused by a deficiency in lactase enzyme. When the body does not make enough of this enzyme, the lactose from milk is not broken down and thus cannot be absorbed by the small intestine. This causes digestive symptoms such as abdominal pain, abdominal bloating, gas, diarrhea, and nausea.
Lactase deficiency is not necessarily the same thing as lactose intolerance. In other words, some people with a lactase deficiency may not have symptoms of lactose intolerance. Contrary to popular belief, most people with lactose intolerance can tolerate some amount of lactose in their diet. Up to 250 ML of milk can be tolerated by most adult lactose intolerants. They are not truly “intolerant” but could more accurately be called lactose sensitive.
Lactose Intolerance is the Normal State
Many people opposed to consuming milk have correctly pointed out that ingesting milk at an advanced adult age is highly unusual and unique to human beings. The body makes lactase in order for newborn humans to digest the sugar in mother’s breast milk. Once a human baby is weaned from the breast, there would seem to be no need for the body to continue producing the enzyme. Most adult mammals, including humans, only retain a fraction of the intestinal lactase activity of infants who need the enzyme to digest mother’s milk.
Therefore, it should be understood that lactose sensitivity or intolerance is the normal state of most human groups. Europeans are a peculiar exception to this rule and lactose persistence in Europe is the subject of much research.
Milk Allergy versus Lactose Intolerance
Do not confuse lactose intolerance with cow milk allergy. Milk allergy is a reaction by the body’s immune system to one or more milk proteins. This type of reaction can life life-threatening even when just a small amount of milk or milk product is consumed. While milk allergy most commonly appears in the first year of life, lactose intolerance occurs more often in adulthood.
What causes lactose intolerance?
To understand what causes lactose intolerance, we need to understand how an individual develops primary lactase deficiency. This deficiency does not develop all at once but over a period of time. It begins at around age two when the body begins to produce less of the enzyme. However, most children still retain enough enzyme activity to not develop symptoms until late adolescence or adulthood. For example, I myself have a moderate to mild lactose sensitivity but I was able to consume lots of milk with no problems at all until I was in my early to mid-twenties (I cannot precisely remember). This type of primary lactase deficiency most likely has a genetic link and if you are lactose intolerant, it may be because you inherited a gene from your parents that made it likely you would develop primary lactase deficiency. In the future, genetic tests to may be available to identify people who will develop lactose intolerance.
There is also a type of lactase deficiency called secondary lactase deficiency. Secondary lactase deficiency can result from an injury to the small intestine occuring with severe diarrheal illness, celiac disease, Crohn’s disease, or chemotherapy. This type of lactase deficiency can occur at any age but is more common in infancy.
Infants born prematurely may have lactase deficiency because an infant’s lactase levels do not increase until the third trimester of pregnancy.
Who is at risk for lactose intolerance?
Assuming we are talking about primary lactase deficiency, then lactose intolerance or sensitivity is a common condition. Among Americans, certain ethnic populations are more likely to develop lactose intolerance, such as African Americans, Hispanic Americans, American Indians, and Asian Americans. Those of Northern European descent are least likely to develop it.
What are the symptoms of lactose intolerance?
People with lactose intolerance may feel uncomfortable 30 minutes to 2 hours after consuming milk and milk products. Symptoms range from mild to severe, based on the amount of lactose consumed and the amount a person can tolerate.
Common symptoms include
- abdominal pain
- abdominal bloating
How do Doctors Diagnose Lactose Intolerance?
You may think you have lactose intolerance because you have the associated digestive symptoms, but it is difficult to diagnose based on symptoms alone. Other conditions, such as Irritable Bowel Syndrome, can cause similar symptoms. After taking your medical history and performing a physical exam, the first thing your doctor is likely to do, should lactose intolerance be suspected, is to recommend that you eliminate all milk and milk products from the your diet for a short time to see if your symptoms go away. If this does not make it clear that milk is the problem, medical tests may be necessary. There are two tests are commonly used to measure the digestion of lactose.
Hydrogen Breath Test. For this test, the patient drinks a a lactose-loaded beverage and then the patient’s breath is analyzed at regular intervals to measure the amount of hydrogen. Your breath normally contains very little hydrogen. However, undigested lactose produces high levels of hydrogen. Since smoking and some foods and medications may affect the accuracy of the results, your doctor may advise you to avoid certain foods and medications prior to the test to make sure they do not interfere with the results.
Stool Acidity Test. This test is used for infants and young children. Undigested lactose creates lactic acid and other fatty acids that can be detected in a stool sample. Glucose may also be present in the stool as a result of undigested lactose.
As stated, lactose intolerance is uncommon in infants and children younger than 2, so a health professional should by very careful in determining the cause of a child’s digestive symptoms.
How is lactose intolerance managed?
The body’s ability to produce lactase cannot be changed but lactose intolerance or sensitivity can be managed by dietary changes. The difficulty in managing it and your success in doing so will depend on how severe your sensitivity to lactose is.
The amount of change needed in the diet depends on how much lactose a person can consume without symptoms. For example, one person may have severe symptoms after drinking a small glass of milk, while another can drink a large glass without symptoms. Others can easily consume yogurt and hard cheeses such as cheddar and Swiss but not milk or other milk products.
Yogurt and hard cheese do have lower levels of lactose than other dairy products, and the Dietary Guidelines for Americans 2005 recommends that people with lactose intolerance choose these types of milk products. Choose yogurt with active and live bacterial cultures. When this type of yogurt enters the intestine, the bacterial cultures convert lactose to lactic acid which may cause the yogurt may be better tolerated than a yogurt without live cultures. Remember that frozen yogurt does not contain live bacterial cultures.
I mentioned that I have some degree of lactose sensitivity. However, I can usually eat ice cream and enjoy most other dairy products and moderate levels with no symptoms. I can even drink moderate amounts of milk, but I would never down a large glass! Similar to the anecdotal experience of others, I find my tolerance to be inconsistent, so that I can at times tolerate larger amounts of milk or dairy products. Some people speculate that they develop a tolerance if they have a small amount of dairy each days and/or slowly increase this amount. If this is true, it has nothing to do with the body begining to secrete more lactase, and may have more to do with chanages in gut bacteria. Undigested lactose undergoes baterial fermentation in the gut, but keep in mind it is this fermentation that produces many of the unpleasant symptoms.
So, gradually introducing small amounts of milk or milk products may help you adapt to them with fewer symptoms. As well, some people can better tolerate milk or milk products by taking them with meals. This will not work for everybody, however.
Lactose-free and lactose-reduced milk and milk products, available at most supermarkets, are identical to regular milk except that a lactase enzyme has been added. If you absolutely must have milk, then these products may be your answer. If it is ultra-pateurized, lactose-free or lactose reduced milk remains fresh for about the same length of time or longer than regular milk. Keep in mind that it may have a slightly sweeter taste. This is because the lactose has been broken down to simple sugars which can be detected by the taste buds.
There is no FDA definition for the terms “lactose free” or “lactose-reduced,” but the labels on these products must be truthful and not misleading. This means a lactose-free product should not contain any lactose, and a lactose-reduced product should be one with a meaningful reduction. A lactose-reduced product may still contain lactose that could cause symptoms.
Be aware that lactose-free or lactose reduced milk will in no way protect a person with a milk-protein allergy. The protein remains in the milk and is unchanged.
If you still experience symptoms after dietary changes or if you just want to be able to occassionaly enjoy a nice glass of chocolate milk or a big bowl of ice cream, you can take over-the-counter lactase enzyme drops or tablets. Two reccomendations are Kirkland Signature Fast Acting Lactase and Best Naturals Fast Acting Lactase Enzyme Tablet. The Kirkland product is much stronger than the Best Naturals product and therefore more expensive. Choose a product that meets you needs. If your symptoms are not that severe and you can tolerate small amounts of dairy, you may not need the stronger product.
Taking the tablets or a few drops of the liquid enzyme when consuming milk or milk products may make these foods more tolerable for people with lactose intolerance. Here, I will give you personal advice based only on my experience, but also backed up by others: The recommended dosages of these products may not be enough for every person. If a lactase pill or drop does not work for you, it may be that you need to use much more of it. There is no harm in this except for the fact that these supplements are expensive and if you have to use a lot of them, it can become costly to consume a lot of dairy. As well, as I mentioned, different products have different strengths, but most people are not aware of this. If one product does not work for you, you may be better off choosing a stronger product rather than taking huge amounts of the weaker product.
What other products contain lactose?
I would be remiss in telling you to manage lactose intolerance by reducing your consumption of lactose-containing foods if I did not also tell you what foods contain lactose. Obviously, any food that is made from milk may contain large amounts of lactose. But, since milk and milk-products are often added to processed foods, you should be aware of the many types of foods that may contain at least small amounts of lactose such as:
* bread and other baked goods
* waffles, pancakes, biscuits, cookies, and mixes to make them
* processed breakfast foods such as doughnuts, frozen waffles and pancakes, toaster pastries, and sweet rolls
* processed breakfast cereals
* instant potatoes, soups, and breakfast drinks
* potato chips, corn chips, and other processed snacks
* processed meats, such as bacon, sausage, hot dogs, and lunch meats
* salad dressings
* liquid and powdered milk-based meal replacements
* protein powders and bars
* non-dairy liquid and powdered coffee creamers
* non-dairy whipped toppings
You can find possible sources of lactose in food by checking the ingredients listing on food labels. If any of the following words are listed on a food label, the product contains lactose:
- milk by-products
- evaporated milk
- condensed milk
- non-fat dried milk power
- milk solids
- dry milk solids
Lactose is also used in some prescription medicines, including birth control pills, and over-the-counter medicines like products to treat stomach acid and gas. These medicines will tend to only cause symptoms in those with severe lactose intolerance.
Raw Milk and Lactose Intolerance
FDA warns consumers not to drink raw, or unpasteurized, milk. “Raw milk advocates claim that pasteurized milk causes lactose intolerance,” says John Sheehan, Director of FDA’s Division of Plant and Dairy Food Safety. “This is simply not true. All milk, whether raw or pasteurized, contains lactose, and pasteurization does not change the concentration of lactose nor does it convert lactose from one form into another.”
Raw milk advocates also claim that raw milk prevents or cures the symptoms of lactose intolerance. Arguing that raw milk contains Bifidobacteria, they claim these microorganisms are beneficial (probiotic) and create their own lactase, which helps people digest the milk. It is true that raw milk can contain bifidobacteria, but when it does, the bacteria come from fecal matter (animal manure). Do I really need to tell you any more?
Raw milk may be even more dangerous for those with lactose intolerance since they may attribute syptoms to lactose that are actually caused by pathogenic organisms in the milk which, in some cases, can cause life-threatening illness.
Lactose Intolerance and Calcium and Vitamin D Intake
Milk and milk products contain a large amount of calcium and other nutrients. In regards to calcium, despite many reports to the contrary, they are also very good sources for the body. Calcium is essential for the growth and repair of bones at all ages. A shortage of calcium intake in children and adults may lead to fragile bones that can easily fracture later in life, a condition called osteoporosis.
The following table lists the recommended calcium intake by age group.
|Age group||Amount of calcium (mg) to consume daily|
|0–6 months||210 mg|
|7–12 months||270 mg|
|1–3 years||500 mg|
|4–8 years||800 mg|
|9–18 years||1,300 mg|
|19–50 years||1,000 mg|
|51–70+ years||1,200 mg|
Source: Adapted from Dietary Reference Intakes, 2004, Institute of Medicine, National Academy of Sciences.
Pregnant or breastfeeding need between 1,000 and 1,300 mg of calcium daily.
If you must severly lmited your intake of milk and milk products, then getting enough calcium from other food sources may become important. Non-milk products that are high in calcium include fish with soft bones such as salmon and sardines and dark green vegetables such as spinach.
The following table list the calcium content of common foods followed by amounts of calcium in common dairy foods.
|Non-milk Products||Calcium Content|
|Rhubarb, frozen, cooked, 1 cup||348 mg|
|Sardines, with bone, 3 oz.||325 mg|
|Spinach, frozen, cooked, 1 cup||291 mg|
|Salmon, canned, with bone, 3 oz.||181 mg|
|Soy milk, unfortified, 1 cup||61 mg|
|Orange, 1 medium||52 mg|
|Broccoli, raw, 1 cup||41 mg|
|Pinto beans, cooked, 1/2 cup||40 mg|
|Lettuce greens, 1 cup||20 mg|
|Tuna, white, canned, 3 oz.||12 mg|
|Milk & Milk Products||Calcium Content|
|Yogurt, plain, low-fat, 1 cup||415 mg|
|Milk, reduced fat, vitamin D-fortified, 1 cup||285 mg|
|Swiss cheese, 1 oz.||224 mg|
|Cottage cheese, 1/2 cup||87 mg|
|Ice cream, 1/2 cup||84 mg|
Source: Adapted from U.S. Department of Agriculture, Agricultural Research Service. 2008. USDA National Nutrient Database for Standard Reference, Release 21.
* Lactose intolerance is the inability or insufficient ability to digest lactose, a sugar found in milk and milk products.
* Lactose intolerance is caused by a deficiency of the enzyme lactase, which is produced by the cells lining the small intestine.
* Not all people with lactase deficiency have digestive symptoms, but those who do may have lactose intolerance.
* Lactose maldigestion may sometimes be a better term than intolerance since most people with lactose intolerance can tolerate some amount of lactose in their diet. When consumption of liquid dairy products reach a couple of servings per day or more, some individuals will benefit of the use of products with reduced lactose content (hydrolyzed lactose, fermented dairy products).
* Yoghurt is well tolerated by lactose intolerant individuals, even pasteurized yoghurt.
* People with lactose intolerance may feel uncomfortable after consuming milk and milk products. Symptoms can include abdominal pain, abdominal bloating, gas, diarrhea, and nausea.
* Symptoms of lactose intolerance resemble those of some other gastrointestinal dysfunctions such as functional bowel disorders and other maldigestions.
* The symptoms of lactose intolerance can be managed with dietary changes.
* Getting enough calcium and vitamin D is a concern for people with lactose intolerance when the intake of milk and milk products is limited. Many foods can provide the calcium and other nutrients the body needs.
* Talking with a doctor or registered dietitian may be helpful in planning a balanced diet that provides an adequate amount of nutrients—including calcium and vitamin D—and minimizes discomfort. A health professional can determine whether calcium and other dietary supplements are needed.
* Milk and milk products are often added to processed foods. Checking the ingredients on food labels is helpful in finding possible sources of lactose in food products.
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