Lactose Intolerance: Why the Cramps?

Updated: Mar 1, 2021

By: Silvia DiPaola, Contributing Writer

Those with lactose intolerance may immediately regret having eaten ice cream when they are hit with the abdominal cramps, bloating, and diarrhea, although it may taste so good in the moment. However, why exactly do our bodies decide to do this to us? (Hint: It involves your favorite subject -- biology!)

You may recall from the principles of biology that long chains of monosaccharides, or simple sugar molecules, form carbohydrates. Lactose, in particular, is a disaccharide, which is two monosaccharides (glucose and galactose, to be specific) linked via a covalent bond. The body breaks down disaccharides, like lactose, into monosaccharides, like glucose so that they can be used for energy purposes. Lactose is found in many everyday dairy products, including cow's milk, goat's milk, yogurt, cheese, and ice cream.

Now that we know the biology behind lactose, we can learn why some people are intolerant. Saccharides are normally broken down by specific enzymes that work on them only. Only when lactose is broken down can it be used by the body for energy. Those who are lactose intolerant may lack the lactase enzyme in the small intestine which breaks down lactose into its constituent parts, galactose and glucose. More commonly, lactose intolerant may be able to produce lactase, but in insufficient quantities. Thus, the lactose from the dairy products you consume is not broken down in the small intestine like it should be; instead, it travels whole to the large intestine, where your gut microbiome digests it. However, the bacteria in the colon produce excess amounts of gas when they break down lactose, which contributes to the bloating, abdominal cramps, and/or gassiness you may feel hours later. The pain may vary in severity and duration from person to person. Those who are lactose tolerant have their lactose broken down in the small intestine by enzymes, and no excess gas is produced, which is why they have no symptoms after eating dairy products.

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What causes lactose intolerance?

There are genetic and non-genetic related causes. The primary cause is lactose non-persistence, where the small intestine produces less lactase after infancy. This is because infants produce a great deal of lactase during their first year or so of life, but the individual may stop producing enough lactase as they start transitioning to regular foods. This may cause them to be lactose intolerant when they are older. Some may simply not inherit the gene that allows their bodies to produce lactase. Moreover, injury to the small intestine through Crohn’s or Celiac disease may cause your small intestine to produce less lactase. If the injury is treated, you may be able to produce lactase in sufficient quantities again.

Unfortunately, there is no way to “cure” lactose intolerance; the only way to treat it is through taking a dietary supplement like Lactaid or outright ending consumption of dairy products with lactose in them. Lactaid contains the lactase enzyme that your body is not producing correctly, allowing it to break down lactose normally in the small intestine.

It may be hard to avoid ingesting lactose as it is so prevalent in the standard dairy products on the market. However, there are many lactose-free products out there, like special Lactaid milk or regular milk without lactose as indicated by the label. When buying products like ice cream, cheese, and milk, you should check the ingredients and see if it says it is lactose-free; if not, you probably should not be consuming it due to the pain you may have later. There are also vegan options available to those looking to maintain a lactose-free diet. However, vegan milk alternatives tend to lack calcium and vitamin D, so be wary of your micros and macros.

Thus, being lactose intolerant is simply a matter of whether your body wants to produce the lactase enzyme or not. It may be highly frustrating, but there are ways around it. And you are not alone: 65% of the global population will have a reduced ability to digest lactose after infancy. Most do not even know if they are lactose intolerant, as it may only be a mild intolerance. If you are one of the unlucky to have a severe intolerance, sit down and reward yourself with some ice cream (hopefully it is lactose-free)!