Lactose Intolerance

I have been reacting to all dairy except for mozzarella and yogurt for as long as I remember. Raised on organic Edensoy soymilk and frozen yogurt, I never felt the urge to consume dairy, aside from cheese (hm, cheese) or the occasional ice cream treat. Lactose intolerance seems to have become more popular now than when I was growing up, so I would like to go over why some of us can tolerate dairy, whereas it can be quite the uncomfortable experience for others.


What is Lactose Intolerance?


Hydrolysis of lactose to galactose and glucose via the lactase enzyme

Hydrolysis of lactose to galactose and glucose via the lactase enzyme

Our ability to digest the carbohydrates of milk varies widely from person to person, with prevalence differing according to ethnicity. Lactase is the enzyme required to digest lactose, a milk sugar. When lactose comes into contact with its enzyme lactase, lactose is split into absorbable components: glucose and galactose. As we get older our ability to produce the enzyme lactase decreases in about 75 percent of people, resulting in high rates of lactose intolerance within the general population.

My artistic interpretation of lactose-consuming gut bacteria

My artistic interpretation of lactose-consuming gut bacteria

Without lactase (aka the enzyme required to absorb dairy) unabsorbed lactose in the gut draws water into the intestines, resulting in diarrhea, while intestinal bacteria use some of the lactose for their own energy producing gas and intestinal irritants. Other common symptoms of lactose intolerance after the consumption of dairy include nausea, pain, and excessive gas.

Degrees of intolerance to dairy varies widely between individuals. Some can tolerate a glass or two a day of milk until they get symptomatic, whereas others can feel the effects of undigested lactose after a little piece of cheese. In rare cases people are unable to tolerate any amount of dairy. Milk sensitivity can also be due to an allergic reaction to the dairy protein and, unlike the lactose intolerant, these individuals are typically unable to tolerate cheese or yogurt. This is a response of the immune system and is not the same thing as lactose intolerance.


Why can some people eat certain cheeses or yogurt?


For some people intolerant to dairy, the consumption of yogurt, aged cheese, or mozzarella may produce minimal or no discomfort.  The production of these products involve the fermentation of milk, and percentage of lactose content in dairy product is significantly lower in fermented foods. The bacteria or molds used to ferment the dairy into yogurt digests lactose in the process. The bacteria in some yogurts may also find residence in the intestinal tract during digestion, thus further reducing the uncomfortable consequences of lactose intolerance. It is important to note that some yogurts do contain added milk solids and therefore also contain additional lactose, so make sure to read the labels on your yogurt.


How will I know if I’m lactose intolerant?


For some, the inability to digest the milk sugar lactose is obvious, due to the digestive consequences in their digest. For others, it is not quite so obvious, as the symptoms are minimal and they may have developed a tolerance to the milk. The most common lab test available for lactose intolerance is called the hydrogen breath test, the measurement of hydrogen in your breath after ingesting a certain amount of lactose. However, if you feel like your digestion could improve and you have any of the symptoms mentioned above (especially bloating), the following steps may be of use to you whether or not you decide to do the hydrogen breath test:

  1. For the first three days consume what you would consider a normal amount of dairy every day. Record your diet and any digestive symptoms you feel during those three days (I would suggest carrying a little notebook with you).

  2. Eliminate all dairy from your diet completely for four to six weeks. Record your diet and how you feel (I would include digestion and energy) for the last 3 days.

  3. After four to six weeks introduce dairy. Eat a good amount of dairy every day (including milk), taking notes of the state of your digestion for three to five days or until intolerance is obvious, whichever comes first.

  4. If this test proved positive for the inability to digest lactose, dairy elimination may offer a more comfortable existence for you. However, it is important to note that dairy products offer a significant source of calcium in many diets, so it is important to ensure sufficient calcium is ingested from other non-dairy sources.

  5. If on a dairy free diet, I would suggest testing out yogurt and mozzarella as well as goat cheese products, as they all have lower lactose contents. Another option with trying is lactose-free (lactase-treated) milk or taking lactase enzymes before ingesting any dairy products.

Hope this provides some answers and clarity regarding the lactose intolerant. Remember there are other sources of dietary calcium, and you may be absorbing very little of the calcium from dairy if you are unable to properly digest milk products.





Alm, L (1982). Effect of fermentation on lactose, glucose, and galactose content in milk and suitability of fermented milk products for lactose intolerant individuals. Journal of Dairy Science, 65(3): 346-52.

Sizer, F., Whitney, El., Piche, L. (2009). Nutrition: Concepts and Controversies (1st Canadian ed). Toronto, Ontario: Nelson Education Ltd.