The Evolutionary Case Against Adult Dairy Consumption
From an evolutionary perspective, the ability to digest milk beyond infancy is a relatively recent anomaly. Like all mammals, early humans weaned off their mother's milk and ceased producing the enzyme lactase, which is required to break down the milk sugar, lactose. The trait of lactase persistence, which allows some adults to continue digesting milk, is the result of a genetic mutation that became common only within the last few thousand years, mostly in populations with a long history of dairy farming. For most of human history, and for a large portion of the current global population, consuming dairy as an adult is not the biological norm.
The Digestive Discomfort of Lactose Intolerance
Lactose intolerance is the most common and direct reason for adverse reactions to dairy. It is caused by the body's insufficient production of lactase, leading to lactose malabsorption. When undigested lactose reaches the large intestine, gut bacteria ferment it, resulting in a variety of unpleasant gastrointestinal symptoms.
Common symptoms of lactose intolerance include:
- Bloating
- Gas
- Diarrhea
- Stomach cramps
The prevalence of lactose intolerance varies dramatically across ethnic groups, with higher rates observed in people of African, Asian, and Native American descent compared to those of Northern European descent. In some Asian populations, for example, 80% to 90% of lactase activity is lost shortly after weaning. For individuals with this condition, consuming dairy is a direct path to discomfort.
Hormonal and Potential Cancer Risks
Dairy products contain naturally occurring hormones, including estrogens and insulin-like growth factor-1 (IGF-1), which have raised concerns about potential health impacts. Some studies have linked high dairy consumption to an increased risk of certain cancers, including prostate cancer in men and breast and ovarian cancers in women. For example, one review suggested a 35% lower prostate cancer risk for men on a vegan diet compared to non-vegetarians. These potential links are often attributed to the hormones present in dairy, although research is ongoing and the connections are complex.
Saturated Fat and Cardiovascular Health
Many dairy products, particularly full-fat varieties and cheese, are major sources of saturated fat in the average diet. Diets high in saturated fat can increase levels of LDL ('bad') cholesterol, which is a key risk factor for heart disease. While recent research has complicated the long-held view on saturated fat, high consumption of full-fat dairy is still a concern for individuals with or at risk for cardiovascular disease. Choosing lower-fat dairy or plant-based alternatives can help reduce saturated fat intake.
The Dairy-Inflammation Debate and Skin Health
The relationship between dairy and inflammation is debated, with some studies suggesting an anti-inflammatory effect, particularly from fermented products, while others link dairy to increased inflammatory markers. However, many people report a connection between dairy intake and inflammatory skin conditions. For instance, dairy is frequently associated with acne and has been identified as a trigger for conditions like eczema and psoriasis. While the exact mechanism isn't fully understood, many individuals find that cutting dairy improves their skin health.
Making the Switch: Dairy vs. Plant-Based Alternatives
For those considering reducing or eliminating dairy, an abundance of plant-based alternatives can provide similar or superior nutrition. The following table compares common nutrients and characteristics of dairy milk and its popular alternatives.
| Feature | Dairy Milk (Cow's Milk) | Plant-Based Alternatives (e.g., Soy, Almond, Oat) |
|---|---|---|
| Primary Sugar | Lactose | Varies (often contains no lactose) |
| Saturated Fat | Varies, can be high (e.g., whole milk) | Generally lower or non-existent |
| Hormones | Contains naturally occurring hormones | Free from animal hormones |
| Calcium | Naturally high, often fortified | Often fortified to match or exceed dairy levels |
| Protein | Complete protein source (~8g/cup) | Varies; soy milk is a complete protein, others are lower |
| Fiber | No fiber | Often contains dietary fiber |
| Cholesterol | Contains cholesterol | Cholesterol-free |
| Environmental Impact | High water and land use, methane emissions | Generally lower impact, varies by source |
Abundant Non-Dairy Sources of Essential Nutrients
Addressing nutritional needs without dairy is straightforward with a balanced, plant-rich diet. Key nutrients like calcium, protein, and vitamin D are widely available from non-dairy sources.
Non-dairy sources of calcium:
- Fortified Plant Milks: Soy, almond, and oat milks are often fortified with calcium and vitamin D.
- Leafy Greens: Excellent sources include kale, collard greens, and bok choy.
- Legumes: White beans, chickpeas, and lentils provide good amounts of calcium.
- Tofu: Tofu that is made with calcium sulfate is a powerful calcium source.
- Nuts and Seeds: Almonds, chia seeds, and sesame seeds (tahini) are rich in calcium.
- Fortified Juices and Cereals: Many breakfast items have added calcium.
Plant-based sources of protein:
- Legumes: Lentils, beans, and peas are packed with protein.
- Soy Products: Tofu, tempeh, and edamame are complete protein sources.
- Nuts and Seeds: Nuts and seeds provide healthy fats and protein.
- Whole Grains: Quinoa and amaranth are complete proteins.
Conclusion
While dairy has long been a dietary staple in many cultures, the notion of its universal health benefits is increasingly questioned. The prevalence of lactose intolerance, potential links to chronic diseases like certain cancers and heart disease, and adverse effects on skin and gut health provide a strong counter-narrative for why humans are not supposed to eat dairy. An informed, personalized approach to nutrition, supported by a wide variety of dairy-free, nutrient-rich foods, allows for a healthy and thriving diet that avoids these potential downsides.
