Essential for the health and development of babies, lactose is the primary sugar contained in the breast milk of mammals. However, unlike most mammals and even our nomadic ancestors, modern diets have evolved to prominently include milk and milk-based products for consumption by adults. While the vast majority of infants can properly break down lactose, many people progressively lose this digestive ability as they grow older. Experts estimate that approximately 68% of the world population suffers from lactose malabsorption, commonly known as lactose intolerance.
In order to metabolize lactose, a sufficient quantity of the enzyme lactase must be available within the small intestine. However, according to geneticists, humans could not produce lactase beyond the weaning period until a genetic mutation emerged approximately 10,000 years ago. Over millennia, this "lactase persistence" trait has spread to populations around the world through the process of natural selection. However, this does not mean it is uniformly distributed. Among ethnicities, it is most common among those descended from northwestern Europeans, 89 to 96% of whom produce ample lactase into adulthood. However, the prevalence of the gene drops to between 15 and 54% for those descended from southeastern Europeans and is far lower for those descended from Africans, East Asians, and Native Americans.
For those of us who are not fortunate enough to have inherited the lactase persistence trait, the consumption of dairy products produces a wide variety of symptoms that all stem from the presence of lactose in the latter stages of the digestive tract. When undigested lactose passes through the small intestine, it reaches the large intestine intact where it interacts with your gut bacteria. Similar to the mechanism of brewing beer that gives the beverage its trademark fizz, fermentation begins inside your colon and produces large quantities of gas, which leads to abdominal bloating and flatulence. In this process, the gut microbiota also produce excess short-chain fatty acids, which result in stomach cramps, nausea, and frequent, liquidy bowel movements. In addition to these uncomfortable gastrointestinal symptoms, lactose intolerant individuals who consume milk products can sometimes experience fatigue, brain fog, headaches, and joint pain.
In good news, lactose intolerance is not the same as a milk allergy. With the right tools, even individuals with this digestive enzyme deficiency can indulge responsibly in milk-based foods. Lactose-free milk is available for purchase from most grocery stores. In addition, lactase supplements can help you more effectively break down lactose and limit the digestive distress you might normally associate with dairy products. With the help of these advances in modern treatment of lactose intolerance, it is possible for some individuals to reintroduce cheese, butter, and ice cream back into their diet in moderation.
