Lactose Intolerance: How to Diagnose and Manage It Effectively?

What is lactose intolerance, and how does it manifest?

Lactose intolerance is the inability to digest lactose, a sugar naturally found in milk and dairy products. It results from insufficient production of lactase, the intestinal enzyme responsible for breaking down lactose into absorbable glucose and galactose. When undigested, lactose reaches the colon, where it is fermented by bacteria, producing gases and acids that cause symptoms. These symptoms generally appear 30 minutes to 2 hours after consuming lactose:

• Bloating and intestinal gas.
• Abdominal pain or cramps.
• Watery diarrhea.
• Nausea, and more rarely, vomiting.

The severity of symptoms depends on the amount of lactose ingested and the residual level of lactase. Most people with lactose intolerance can tolerate small amounts of lactose (equivalent to half a glass of milk), especially when consumed with other foods. This condition is hereditary: variants of the LCT gene that reduce lactase production after childhood are passed down from one generation to the next. It is widespread worldwide—approximately 65 to 70 percent of the adult population exhibits some form of reduced lactase activity—but its prevalence varies considerably: very high in East Asia and sub-Saharan Africa, and lower in Northern Europe, where the persistence of lactase developed as an evolutionary adaptation to dairy farming.

How is lactose intolerance diagnosed?

Several methods can be used to confirm the diagnosis:

• Exhaled hydrogen test: the most reliable and widely used. After ingesting a dose of lactose, the hydrogen produced by colonic fermentation is measured in the breath.
• Lactose tolerance test: measures blood glucose levels before and after ingesting lactose. In cases of intolerance, blood glucose levels do not rise as expected.
• Genetic test: identifies variants of the LCT gene associated with lactase non-persistence.

Self-diagnosis by elimination (cutting out dairy products for 2 weeks) can also serve as an initial guide, to be confirmed by a medical test. Restored digestive comfort after eliminating lactose is a strong indicator.

How can lactose intolerance be managed on a daily basis?

Management relies on three complementary strategies:

• Reduce or eliminate dairy products by identifying your personal tolerance threshold.
• Choose fermented dairy products (yogurt, kefir): fermentation partially breaks down lactose, improving tolerance.
• Take lactase supplements at the start of meals containing lactose to replace the missing enzyme.

Reading labels is essential: lactose is hidden in unexpected products (white bread, deli meats, medications, packaged soups). Specific probiotics (Lactobacillus acidophilus) can improve lactose digestion by promoting its breakdown in the colon.

What are the alternatives to dairy products for people with lactose intolerance?

Several substitutes are available to meet culinary and nutritional needs:

• Fortified plant-based milks: almond, soy, oat, rice, coconut—check for added calcium and vitamin D.
• Plant-based yogurts made from soy or coconut, enriched with cultures.
• Aged cheeses (Parmesan, Cheddar, Gruyère): very low in lactose, often well tolerated.
• Lactose-free products (labeled “lactose-free”): identical to standard dairy products, with added lactase.

How can you prevent deficiencies caused by cutting out dairy?

Eliminating dairy products without replacing them puts you at risk of calcium and vitamin D3 deficiencies, which are essential for bone health. To compensate:

• Calcium: green vegetables (broccoli, kale), almonds, calcium-fortified tofu, sardines with bones, fortified plant-based milks.
• Vitamin D3: regular sun exposure and supplementation, which is essential if dairy products were your usual main source.
• Calcium supplementation may be considered if dietary intake remains insufficient, always under medical supervision.

Nutritional monitoring by a dietitian is particularly helpful for children, pregnant women, and older adults, who are more vulnerable to the bone-related consequences of calcium deficiency.