If you've always been able to eat dairy and suddenly find that you can't do so anymore, you may be lactose intolerant. While sudden lactose intolerance isn't common or likely, it's certainly possible. There are a few things you can do to determine whether you're actually lactose intolerant, and if so, how to cope with your symptoms.
Lactose intolerance is a commonly over-diagnosed condition, notes a 1999 article in the "American Journal of Clinical Nutrition." True lactose intolerance results from an inability to produce sufficient quantities of the digestive enzyme lactase, which breaks down milk sugar. Typically, humans produce large quantities of lactase early in life, and lactase production often decreases slowly with age. As such, it's quite common to become lactose intolerant over a period of time. Sudden lactose intolerance, however, is much more rare.
If you think you've suddenly become lactose intolerant, the cause is likely an injury or illness of the intestine, explains MayoClinic.com. Inflammations of the gastrointestinal tract can affect your ability to produce lactase, and leave you with symptoms of lactose intolerance including gas production, cramping and bloating upon consuming dairy. If you've experienced an illness, intestinal upset or injury, you may very well have become temporarily lactose intolerant. Generally, your symptoms will resolve over time.
There are many other things that can present similarly to lactose intolerance, however, and are more likely to cause sudden onset of symptoms -- particularly if you haven't been ill recently. Pregnancy changes the way your digestive tract works, for instance. This can cause you to experience increased gas and cramping upon consumption of a variety of foods, including dairy. It's not true lactose intolerance, however. Further, gastrointestinal upset that doesn't affect lactase production can still cause increased gas and cramping upon consumption of dairy.
If you've truly become lactose intolerant -- your doctor can help you verify whether this is the case -- you have a few options available to you that will help increase your comfort and allow you to consume dairy products. Lactase supplements, which are available as over-the-counter pills, provide a temporary supply of the lactase enzyme and allow you to use dairy products as long as you take a pill with the dairy. You can also try lactose-free dairy, which has been treated with lactase enzyme.