The notion that milk is crucial for adult health is a myth perpetuated by the dairy industry, according to a doctor and gut health expert. Dr. Alan Desmond argues that milk is fundamentally designed for infants and that most adults globally are unable to digest it comfortably.
Desmond explains that human breast milk contains lactose, a sugar necessary for infant growth. This sugar is broken down by an enzyme called lactase. However, after weaning, the body's production of lactase typically declines. By adulthood, about two-thirds of the world's population produces insufficient lactase to digest lactose effectively. When these individuals consume cow's milk, undigested lactose can ferment in the colon, leading to symptoms such as gas, bloating, cramping, abdominal pain, and diarrhea. He emphasizes that this difficulty in digesting milk is the biological norm for adults, not an anomaly.
The expert also questions the established link between milk consumption and bone health, a message heavily promoted by the dairy industry. While milk is a source of calcium, essential for bones, large-scale studies and meta-analyses have not demonstrated that higher milk intake reduces fracture risk. Desmond points out that calcium is a mineral absorbed by plants from the soil and then passed to cows. He asserts that numerous other foods are rich in calcium, including leafy greens like kale and spring greens, beans, and nuts. For instance, a 100g serving of calcium-set tofu can provide as much calcium as a 300ml glass of cow's milk, and most plant-based milks are fortified to match cow's milk's calcium content per serving.
Furthermore, bone health is not solely dependent on calcium. Vitamin D, primarily synthesized through sunlight exposure or obtained via supplements, and weight-bearing exercises such as brisk walking, running, or resistance training, are also critical for maintaining bone density and strength throughout life. Desmond concludes that bone strength is built through diet and lifestyle, not exclusively through dairy products.
Regarding fermented dairy products like yogurt, Desmond acknowledges they can be easier to digest and provide protein and calcium. However, he disputes their classification as a "superfood." While yogurt contains some beneficial bacteria, a typical serving includes only a few of the thousands of strains found in the human gut microbiome, and it lacks fiber, a key nutrient for gut microbes. He notes that while yogurt consumers may have healthier habits overall, studies show that simply adding yogurt to the diet without other changes does not lead to significant or sustained weight loss.
Kefir, another fermented dairy drink touted for gut health benefits, also lacks robust scientific backing. Although kefir can alter gut bacteria composition, studies have not consistently linked its consumption to improvements in health markers like blood sugar or inflammation. In contrast, diets rich in fiber and low in meat, regardless of dairy content, have shown significant positive impacts on the microbiome, cholesterol levels, fasting glucose, and markers of inflammation.
Desmond's book, "What Your Doctor Isn’t Telling You About Food," further elaborates on these points, suggesting that while dairy can be part of a healthy diet, it is not an essential component. He advocates for a diverse, calcium-rich diet, regular exercise, adequate vitamin D, and evidence-based nutritional guidance over marketing claims.