A person is lactose intolerant when they no longer makes sufficient quantities of the enzyme lactase. Because the enzyme no longer breaks the lactose sugar down, bacteria in the large intestine do instead. The bacteria release a lot of gas when they do this, which irritates the large intestine and causes the symptoms we observe.
Below is a quick run down to understanding lactose content in foods, and what I’ve done to continue eating awesome dairy food despite my own very inconvenient sensitivity.
What contains lactose?
As a short answer, more than you would think. Obviously ice cream and milk do. Hard cheeses contain very little. I often read that yogurt is well-tolerated by lactose-intolerants due to the bacterial culture, but I do not tolerate yogurt. Sour cream made by traditional methods is low in lactose, but many manufacturers add milk solids.
It gets more complicated. Many foods contain milk powder or whey. Milk powder is 50% lactose by weight, and whey is 10%-70% lactose. Pastries, hot chocolate mixes, pudding mixes, and even Doritos can contain milk powder and whey. Most annoyingly, products do not list the quantity of lactose contained.
Fortunately, several websites tabulate the lactose content of various foods (at least dairy– if you find one for prepared foods, I would love to hear about it). Steve Carper’s Super Guide to Dairy gives a great explanation of the lactose content of a wide variety of dairy products. This link has a decent list.
Circumventing lactose intolerance
Thanks to modern science, we can synthesize the lactase enzyme. The enzyme can be taken as pills and eaten with food, or added to the food as a liquid. I used to take the pills, but as my symptoms progressed, that method became insufficient. The stomach is a mixing chamber, and mixing is imperfect, so enough lactose still got through to cause issues.
After going a year without ice cream or yogurt, I decided to investigate my options. Online, I found the lactase liquid drops, which can be added to any liquid. In 24 hours, these drops reduce the lactose content of a product roughly 70%. I usually add more than the recommended quantity and wait three days to be extra sure. (A side note: I read in the amazon comments that some batches of the enzyme didn’t work; you can test the enzyme’s effectiveness using diabetic glucose test strips. Lactose splits into glucose and galactose, but food doesn’t normally contain glucose; a test strip indicating its presence in a treated food means the enzyme worked. I bought my enzyme in August, and did the test because heat can de-activate enzymes; it was super easy.)
Then I made lactose-free yogurt. I made lactose-free fresh mozzarella cheese (although I wasn’t very good at it). I bought an ice cream maker and made ice cream in any flavor I wanted. I made chocolate mousse. For Thanksgiving, I made ice cream and pumpkin pie with sweetened condense milk and mashed potatoes with sour cream.
Basically, you can add the enzyme to the cream or starting dairy product, let it be for a couple of days, and then cook as you normally would. In milk, the treatment slightly changes the flavor of the milk (it becomes a little cloying, because glucose tastes different than lactose), but in prepared foods I can’t tell the difference. Below are a couple pics of some projects I enjoyed very much. Hopefully this brief run down helps a few of you, or a least gives a picture of our complicated food science lives.