What is the age-related capacity for lactose digestion in humans?

From the Guidelines

Lactose digestion capacity generally decreases with age in humans, but the extent varies widely between individuals, with an estimated 65-70% of the global population having reduced lactose digestion capacity by adulthood 1. Specifically:

• Infants and young children typically have high lactase enzyme levels to digest milk, but lactase production often begins decreasing after weaning, around ages 2-5 1.
• The decrease in lactase production with age is thought to be genetically programmed, with some populations developing genetic mutations allowing continued lactase production into adulthood, likely due to the nutritional benefits of dairy in certain environments 1.
• Older adults (65+) are more likely to be lactose intolerant than younger adults, with the exact incidence of lactose intolerance unknown, but estimated to occur in 70% of the world’s population, particularly in Asia, Africa, and South America 1. To manage reduced lactose tolerance:
• Gradually introduce dairy products to allow gut adaptation
• Choose lactose-reduced dairy or take lactase enzyme supplements before consuming dairy
• Get calcium from non-dairy sources if avoiding milk products It's worth noting that dairy is not considered a daily requirement for all adults in all regions, especially in areas where lactose intolerance is prevalent in adulthood, and some countries do not include a separate dairy group in their food guides, instead including dairy products in a general protein group or as alternative protein sources 1.

From the Research

Age-Related Capacity for Lactose Digestion

• The ability to digest lactose, a disaccharide present in milk and dairy products, decreases with age in most people, except for those of Caucasian descent 2, 3.
• Lactase activity, the enzyme responsible for hydrolyzing lactose into glucose and galactose, decreases at around 4-6 years of age in most individuals, leading to lactose intolerance 2.
• However, some studies suggest that lactase activity may decrease as early as 2 years of age in some populations 4.
• Lactose intolerance is characterized by symptoms such as bloating, flatulence, abdominal pain, and diarrhea, which occur when lactose is not fully digested and reaches the large intestine 2, 3, 4.

Lactose Digestion in Infancy and Adulthood

• In infancy, lactose is an essential source of calories, and lactase expression is high 5, 6.
• As individuals grow older, lactase expression decreases, leading to lactose malabsorption and potentially lactose intolerance 5, 6.
• However, some adults may still be able to consume small amounts of lactose without symptoms, and certain dairy products, such as cheese and yogurt, may be better tolerated due to their lower lactose content or the presence of living lactic acid bacteria 2, 5, 4.

Variations in Lactose Digestion Capacity

• There is considerable variation in lactose digestion capacity among individuals, with some people able to consume larger amounts of lactose without symptoms than others 3, 6.
• The ability to digest lactose is influenced by factors such as lactase expression, intestinal microbiome, and visceral hypersensitivity 6.
• Diagnostic tests, such as genetic and physiological tests, can help identify individuals with lactose malabsorption and intolerance 6.