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My partner has said for years he thinks he's lactose intolerant. He can fairly easily digest skinny milk (i.e. only 0.10 grams of fat per 100ml), as well as goat's cheese. He finds the biggest culprits for upsetting his stomach are yoghurt made with cow's milk (both regular and low-fat) and cow's milk cheeses.
Not sure if this is actually lactose intolerance or a milk allergy. I'm hoping you might be able to explain the difference?
Lactose intolerance occurs because of the loss of the body's ability to produce lactase. Lactose (the sugar found in milk) is made up of two sugar molecules: glucose and galactose. Lactase splits the sugar for proper digestion and absorption. Without being split, the sugars are not broken down in the small intestine and pass to the colon, where they are used by bacteria for food: the byproducts can cause gas, bloating, and sometimes diarrhea.
It is now clear that lactose intolerance is a "dose dependent" issue. Everyone varies in the amount and form of dairy products they can tolerate. Here's some relevant research, from one of my Health & Nutrition Bites: Managing Lactose Intolerance.
Milk allergy is an allergic reaction to the proteins in milk and other dairy products. It is most common with cow's milk but can be a problem for some folks using sheep or goat milk. It is a true allergic reaction, with the body mounting an immune response, and can be quite dangerous.
It is much more common in children, and symptoms include nausea, vomiting, wheezing, hives, bloating, and diarrhea. It can be quite severe, causing anaphylactic shock (thus a risk of death). If your partner believes that he might have an allergy and not lactose intolerance, he should certainly visit his doctor. Here's more information about food allergies.
Thanks for writing,
Timothy S. Harlan, MD, FACP, CCMS