There are dual facets to many issues, such as two sides of a coin, two sides of a story and dual personalities. This is true for nutrition too, where divergent perspectives on specific foods exist, with one often gaining more popularity and becoming the prevailing reality. A clear illustration of this phenomenon can be seen in the case of lactose, the sugar found in milk. In today’s health-conscious climate, lactose intolerance has captured considerable attention from both health professionals and the public alike, with many individuals identifying as lactose intolerant. However, less widely acknowledged is the contrasting perspective known as lactose persistence. This dichotomy revolves around the body’s ability — or inability — to digest lactose, the sugar found in milk and dairy products.

Lactose: Milk sugar

It is a type of sugar found naturally in milk and dairy products. It consists of two simpler sugars, glucose and galactose, linked together. Lactose is the primary carbohydrate in mammalian milk, including human breast milk, and serves as a vital energy source for infants. To be absorbed into the bloodstream and used by the body for energy, lactose must be broken down into its component sugars by an enzyme called lactase, which is produced in the small intestine.

Lactose intolerance: Dairy discomfort

It is a condition where the body is unable to fully digest lactose, which is the sugar found in milk and dairy products. This occurs due to a deficiency of lactase, the enzyme responsible for breaking down lactose into simpler sugars (glucose and galactose) that can be absorbed into the bloodstream. It’s important to note that lactose intolerance is different from a milk allergy, which involves the immune system reacting to proteins in milk rather than the inability to digest lactose.

When lactose intolerance is present, undigested lactose moves into the colon where it interacts with bacteria, leading to symptoms such as bloating, gas, diarrhoea and abdominal discomfort. The severity of symptoms can vary depending on the individual’s level of lactase deficiency and the amount of lactose consumed.

Lactose persistence: The evolutionary advantage

Also known as lactase persistence, it is the continued ability to digest lactose, the sugar found in milk and dairy products, into adulthood. Some individuals continue producing lactase, the enzyme necessary to digest lactose, into adulthood, allowing them to digest lactose and derive nutrition from dairy products without digestive discomfort.

This trait is primarily observed in populations with a long history of dairy farming, such as those of European, African, and Middle Eastern descent. The evolutionary basis for lactose persistence lies in the domestication of animals and the subsequent consumption of their milk. Over generations, communities that relied on dairy developed genetic mutations that allowed them to efficiently digest lactose beyond infancy. Studies have identified specific genetic variants associated with lactase persistence, such as mutations near the LCT (lactase gene) locus on chromosome 2.

Lactose persistence in Indians

The genetic diversity across India means that lactose persistence rates can vary widely between different ethnic groups and geographic regions. For instance, studies have found higher frequencies of lactase persistence among populations with historical ties to pastoralism and dairy farming, particularly in the north and west, where the practice of raising cattle for milk has been longstanding and among some tribal communities. These populations tend to have higher frequencies of lactase persistence compared to southern and eastern parts of India, where dairy consumption traditionally has been lower. Studies have shown that lactase persistence in India is associated with specific genetic variants near the LCT gene, like those found in European and other populations with a history of dairy farming.

As India undergoes rapid socioeconomic changes and dietary habits evolve, the prevalence of lactose persistence and intolerance may also shift. Factors such as urbanisation, increased dairy consumption, and genetic admixture between different ethnic groups could influence the distribution of lactase persistence across the country.

Understanding the distribution and prevalence of lactose persistence provides insights into the genetic diversity and evolutionary history of Indian populations, as well as implications for public health and dietary recommendations in a diverse and dynamic country.

Dairy-free

Amidst the widely promoted idea that humans are the only mammals to consume milk from other mammals, which implies a sense of cruelty, coupled with the widespread availability of lactose-free products and the trendiness of being lactose intolerant, many are drawn to adopt dairy-free lifestyles. However, before making the decision to give up dairy, it’s crucial to carefully consider its nutritional impact on your health.

People who do not consume dairy products, such as milk, cheese, and yoghurt, may be at risk for several common nutritional deficiencies. Here are some key nutrients that dairy-free individuals should pay attention to:

Calcium: Dairy products are a primary source of calcium in many diets. Without dairy, individuals may not get enough calcium, which is essential for bone health and muscle function.

Vitamin D: Dairy products in some countries are fortified with vitamin D, which helps in the absorption of calcium. Without dairy, ensuring an adequate intake of vitamin D becomes crucial, especially if exposure to sunlight (a natural source of vitamin D) is limited.

Protein: Dairy is a significant source of high-quality protein.

Vitamin B12: Dairy products are not a primary source of vitamin B12, but they can contribute to overall intake. Vegans and strict vegetarians who avoid dairy need to find alternative sources of vitamin B12, such as fortified cereals, nutritional yeast, or supplements.

Riboflavin (Vitamin B2): Riboflavin is found in dairy products and is important for energy production and metabolism. It can be obtained from other sources like fortified cereals, almonds, mushrooms, and spinach.

Zinc: Dairy products contain zinc, an essential mineral involved in immune function, wound healing, and protein synthesis. Zinc can be found in other foods such as whole grains, legumes, nuts, and seeds.

Magnesium: While not exclusively found in dairy, magnesium intake may be affected if dairy products are eliminated. Magnesium is important for nerve function, muscle function and bone health.

Still confused?

Conversely, lactose intolerance impacts a substantial number of people worldwide. Moreover, it’s important to note that some people who have difficulty digesting milk may find that they can tolerate yoghurt and certain cheeses. While some may find relief from symptoms when consuming these dairy products, others may still experience discomfort depending on the severity of their intolerance and the specific product consumed. Choosing yoghurt with live and active cultures and opting for aged cheeses may help maximise tolerance for those with lactose intolerance.

Therefore, if you have concerns, it’s advisable to seek guidance from a doctor or nutritionist who can arrange appropriate tests. The lactose tolerance test is typically the primary diagnostic method for lactose intolerance, although alternative tests like hydrogen breath tests and stool acidity tests are also available to indirectly evaluate lactose digestion.

Increasing awareness about individual tolerance levels and promoting inclusivity in dietary choices will continue to shape how societies approach dairy products in the future.

Hena Nafis is a consultant
nutritionist and a public health practitioner with an MPH degree from Harvard University. She is the owner of nutrition and lifestyle clinic Nutrience. You can follow her on Facebook and Instagram
@nutriencebyhenanafis