What is IT?

Lactose intolerance means difficulty digesting lactose (the natural sugar in dairy). Specifically, people with lactose intolerance do not produce or barely produce lactase, the enzyme responsible for digesting lactose.


Estimates peg the number of people in the US with lactose intolerance at 30-50 million. According to the National Institutes of Health: "Approximately 65% of the human population has a reduced ability to digest lactose after infancy. Lactose intolerance in adulthood is most prevalent in people of East Asian descent, affecting more than 90% of adults in some of these communities. Lactose intolerance is also very common in people of West African, Arab, Jewish, Greek, and Italian descent."

According to the Physicians Committee for Responsible Medicine: "Approximately 70% of African Americans, 90% of Asian Americans, 53% of Mexican Americans, and 74% of Native Americans [are] lactose intolerant...Studies showed that a substantial reduction in lactase activity is also common among those whose ancestry is African, Asian, Native American, Arab, Jewish, Hispanic, Italian, or Greek....Overall, about 75% of the world's population, including 25% of those in the U.S., lose their lactase enzymes after weaning."

When does it begin?

At birth, the vast majority of babies produce lactase, the enzyme that digests lactose. However, between 2 and 3 years of age, most gradually stop making it, resulting in lactose intolerance. As we age, we tend to produce less and less lactase.

What are the symptoms?

Symptoms of lactose intolerance, which tend to begin 30-120 minutes after consuming lactose, can include gas, bloating, abdominal cramps, diarrhea, nausea, and vomiting. That said, everyone's body is unique, with different thresholds for the amount of lactose they can tolerate. So, you might be fine after drinking 1/2 cup of cow's milk, whereas someone else could have a problem consuming as little as 2 tablespoons.

does the lactose content of different dairy products vary?

Different dairy products contain different amounts of lactose. Generally, the higher fat and more aged the item, the less lactose it contains. Dairy with the most lactose includes fresh and lower-fat items: skim milk, whey, and dry milk powder. Sweetened condensed milk, cottage and fresh ricotta cheeses, and feta are also high in lactose. Dairy with less lactose includes butter, aged cheeses, and heavy cream.

What is a dairy allergy and how common is it?

In contrast to lactose intolerance, an allergy to dairy is much less common, and involves a sensitivity to milk proteins, rather than milk sugar. According to Food Allergy Research & Education (FARE), 1-2% of young children and .2-.4% of the general population have a dairy allergy.

What should you do if you are lactose intolerant or have a dairy allergy?

If you are lactose intolerant, you can either: 1. avoid all dairy products other than lactose-free versions (to which the lactase enzyme has been added), or 2. take a lactase pill right before consuming dairy. If you are allergic to dairy, avoid all dairy products, including lactose-free versions.