Most of us had milk every day when we were kids. We poured it over our breakfast cereal and drank a big glass at dinner without a problem.
Not so any more. For many adults who grew up on milk, drinking too much can bring on cramps, bloating, gas, even diarrhea - the symptoms of lactose intolerance.
Most people develop some degree of lactose intolerance as they get older. But that doesn't have to mean a dairy-free diet. In fact, including milk and other lactose-containing foods in your diet can actually reduce your symptoms.
Lactose intolerance is the inability to digest and absorb lactose, the natural sugar found in milk and milk products. For lactose to be absorbed from the intestine, it first must be split into two smaller sugar units with the help of a digestive enzyme called lactase.
Everyone is born with lactase. But most of the world's population - with the exception of people of northern European descent - is genetically programmed to stop making large quantities of lactase around the age of 4.
The most common cause of lactose intolerance is the normal result of aging, but it can also result from an illness that injures the intestinal lining such as celiac disease, inflammatory bowel disease or a parasitic infection. In these cases, lactose intolerance is usually temporary and disappears when the bowel is healed.
If you're lactose-intolerant, consuming more lactose than your gut can break down can cause nausea, abdominal pain and distention, bloating, gas and diarrhea within 15 minutes to several hours after eating or drinking foods with lactose.
Symptoms occur because the undigested lactose passes from the small intestine into the large intestine where it is fermented by bacteria that reside there. As they do their job, excess gas is released, causing discomfort. Undigested lactose also draws water into the colon, which can lead to diarrhea.
However, a lactase deficiency doesn't always translate into lactose intolerance. Individuals with a mild lactase deficiency can drink milk with no symptoms at all. Even people with a moderate deficiency of lactase can handle some dairy with few or no symptoms.
On the other hand, people who have a severely reduced amount of lactase will have major symptoms with even small amounts of milk.
Lactose intolerance should not be confused with milk allergy, which has nothing to do with lactose. Rather, it's the body's immune system reacting to a protein in cow's milk. Milk allergy is typically outgrown by the age of 3.
Not everyone who thinks they're intolerant to lactose actually have the condition. A study published this year found that of 353 patients referred to specialists for suspected lactose maldigestion, 53 per cent were able to digest lactose perfectly fine. The researchers speculated that some folks were actually suffering from irritable bowel syndrome, which has similar symptoms.
If you think lactose intolerance is the cause of your digestive distress, don't try to diagnose yourself. The same digestive distress caused by lactose intolerance may be caused by other digestive disorders, some of which can be serious if not treated properly.
The most reliable way to confirm lactose intolerance is the hydrogen breath test. It measures the amount of hydrogen in your breath after consuming 25 grams of pure lactose (equivalent to 500 millilitres of milk). If you're lactose-intolerant, your body will produce more hydrogen than if you are not. (Intestinal bacteria that ferment undigested lactose produce hydrogen gas in the process.)
If have lactose intolerance, you'll need to adjust your diet to relieve your symptoms. The following strategies can help you manage - and prevent - the uncomfortable symptoms of lactose intolerance:
Learn what contains lactose. Lactose is found in milk, yogurt, cream, butter, ice cream and cheese. But it's also in some breads and baked goods, pancake mixes, ready-to-eat breakfast cereals, instant soups, candy, cookies, salad dressings, deli meats, drink mixes and margarine.
Check labels for dairy products or lactose in the ingredient list. Other words that indicate lactose include whey, curds, milk byproducts, dry milk solids and milk powder.
Lactose can also be hidden in prescription and over-the-counter medications. Tell your pharmacist if you have a lactose intolerance.
Reduce dairy. Scaling back your intake of dairy products is the most obvious way to treat lactose intolerance. Luckily, most people with mild or moderate intolerance can handle small portions of milk - up to ½ cup (125 millilitres) - at a time.
Drink milk with meals, rather than on an empty stomach, to slow down digestion and reduce the chances of symptoms.
Yogurt is usually well tolerated. That's because the bacteria used to culture yogurt contain lactase, which breaks down some of the lactose during storage and when it's eaten.
Hard cheeses, such as cheddar, Swiss and Parmesan, have small amounts of lactose and generally cause no symptoms.
If you have a severe lactose intolerance, you will have to avoid all dairy products.
Try lactase-treated products. Lactose-reduced milk is available in grocery stores. These products have been pretreated with lactase and are 99-per-cent lactose-free.
You can reduce the lactose content of dairy products yourself by using lactase enzyme supplements, such as Lactaid, sold in drugstores. Lactaid tablets are taken before meals; Lactaid drops are added to foods.
Train your gut bacteria. Some people find that by slowly increasing the amount of dairy in their diet, they are able to consume larger amounts of lactose without symptoms. Consuming some dairy regularly trains your gut bacteria to process lactose more efficiently, resulting in less gas and diarrhea.
Consider probiotics. A number of studies have found that consuming probiotics - the live bacteria available in yogurt and kefir and as supplements in capsule form - helps to break down lactose and reduce the symptoms of lactose intolerance. If you decide to use a supplement, choose a product that contains at least one billion active cells per dose.
Get enough calcium. If you're cutting back on dairy, be sure to include other calcium-rich foods in your diet such as fortified plant beverages (soy, rice, almond), canned salmon (with bones), almonds, bok choy, broccoli, kale and tofu. Many people with lactose intolerance will need to take a calcium supplement to meet their daily requirement.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.