Do Omnivores Eat Dairy? Understanding Diet and Digestion

December 9, 2025 •

4 min read

While the term 'omnivore' strictly defines an animal that eats both plants and animals, the relationship with dairy is complex. Most mammals stop producing the enzyme lactase after infancy, meaning the ability to consume dairy as an adult is not a universal omnivore trait but rather a genetic adaptation. This adaptation allows omnivores like many humans to include milk and dairy products in their diet, a practice rooted in our co-evolution with domesticated animals.

Quick Summary

This article explains how dairy consumption among omnivores is influenced by evolutionary history and genetics, not just the capacity to eat both plants and animals. It explores why some omnivores, particularly a significant portion of the human population, developed the ability to tolerate dairy into adulthood while many others remain lactose intolerant.

Key Points

Omnivore Definition: An omnivore is an animal that eats both plant and animal matter, but this does not inherently include dairy consumption.
Lactase Persistence: The ability for adult humans to digest dairy is a genetic mutation called lactase persistence, which is not universal among omnivores.
Lactose Intolerance: Most adult mammals, including many humans, are lactose intolerant, meaning they lack the enzyme lactase to properly digest milk sugar.
Human Co-evolution: Dairy became a dietary component for specific human populations who evolved alongside pastoralist practices.
Nutrient Source: For those who can tolerate it, dairy can be a rich source of calcium, protein, and vitamins in a balanced omnivorous diet.
Dietary Flexibility: A truly omnivorous diet is defined by its adaptability, not dependence on dairy, with many alternatives available for those who avoid it.
Processing Effects: Some dairy products, like aged cheese and yogurt, have lower lactose levels due to the production process and are often better tolerated by individuals with sensitivity.

Defining Omnivores and Their Diets

An omnivore is an animal whose diet consists of both plant and animal matter. This broad classification includes a wide variety of species, from bears and pigs to birds like chickens and, of course, humans. Unlike strict carnivores with specialized teeth for tearing meat or herbivores with digestive systems optimized for plant fiber, omnivores have a more flexible system, including both sharp canines and flat molars, to process a diverse range of foods. This adaptability provides omnivores with a significant advantage, allowing them to thrive in diverse environments by capitalizing on whatever food sources are available.

The Role of Dairy in an Omnivorous Diet

For most omnivorous species, especially those in the wild, dairy is not a component of their adult diet. The consumption of milk is a behavior typically reserved for infancy, and after weaning, the production of the enzyme lactase—which is necessary to digest lactose, the sugar in milk—dramatically declines. This natural process, known as lactase non-persistence, results in lactose intolerance in most adult mammals. For example, bears, though omnivorous, do not seek out and consume milk from other species as a regular part of their adult diet.

Humans are a notable exception to this rule. The ability for a significant portion of the adult human population to digest lactose is a result of a genetic mutation called lactase persistence. This mutation became widespread in populations that adopted pastoralism, where domesticated animals provided a new, reliable food source. Over thousands of years, this co-evolutionary process led to the genetic trait for continued lactase production, allowing these groups to consume dairy products without significant digestive distress.

The Digestion of Dairy: A Comparative Look

Digestion of dairy is a prime example of physiological differences among omnivores. While a human with lactase persistence can break down milk sugar in the small intestine, a person with lactase non-persistence or another omnivore would experience fermentation in the large intestine.


Table: Comparison of Dairy Digestion in Omnivores	Feature	Lactase-Persistent Human (Tolerant Omnivore)	Lactase Non-Persistent Human (Intolerant Omnivore)	Wild Omnivore (e.g., Bear)
Lactase Production	Continues into adulthood	Declines after infancy	Declines after infancy
Dairy Digestion	Lactose broken down in the small intestine	Undigested lactose ferments in the large intestine	Undigested lactose would ferment in the large intestine
Common Symptoms	Minimal to none	Bloating, gas, diarrhea, discomfort	Not applicable due to rare consumption
Dietary Adaptation	Enabled by genetic mutation	Often managed by avoiding or limiting dairy	Avoids dairy as part of adult foraging behavior

The Modern Omnivore's Choice

The human diet is arguably the most flexible and diverse of all omnivores. With the advent of agriculture and dairy farming, humans incorporated dairy into their diet as a rich source of calcium, protein, and vitamins. This has led to the wide array of dairy products we see today, from cheese to yogurt, many of which have reduced lactose content due to processing. However, not all humans are physiologically equipped for dairy consumption, and even those who are tolerant may choose to limit their intake for other health or ethical reasons.

Nutritional Considerations for Human Omnivores

For humans, dairy offers a concentrated source of vital nutrients like calcium, potassium, and vitamins A, D, and B12. These nutrients are especially important for bone health and can contribute positively to an omnivore's balanced diet. However, the modern human diet is also faced with potential drawbacks associated with high dairy consumption, including high saturated fat content and potential links to inflammation or certain health issues, though research is ongoing and often debated.

Dairy Alternatives and Diverse Diets

The rise in plant-based milks and dairy alternatives is not just a trend but also a reflection of a deeper understanding of nutrition and individual needs. For human omnivores who are lactose intolerant, choose to avoid dairy for health reasons, or have ethical concerns, a range of fortified alternatives from soy, almond, and oat milk provide an effective means to get comparable nutrients. A truly flexible omnivorous diet does not rely on a single food group but adapts to what is both available and beneficial to the individual's physiology and well-being.

Conclusion

In summary, the question of "do omnivores eat dairy?" is best answered by looking at species-specific biology and evolution. The ability to consume dairy as an adult is not a standard feature of omnivory but a unique genetic adaptation found in certain populations of humans. While dairy has played a significant role in human nutrition, dietary flexibility means that human omnivores can thrive with or without it. For those with lactase persistence, dairy is a nutrient-dense option, but for the majority of the world, dairy alternatives offer a way to get key nutrients without the digestive issues associated with lactose intolerance. The key takeaway is that an omnivore's diet is defined by capacity, not a rigid set of required foods. For further information, consider reading studies on the co-evolution of dairy and humans, such as those found on the National Library of Medicine.

Frequently Asked Questions

An omnivore is an animal that can obtain energy and nutrients from both plant and animal matter. This dietary flexibility allows them to survive in a wider range of environments than herbivores or carnivores.

The ability to consume dairy as an adult is determined by the presence of the enzyme lactase. While all young mammals produce lactase to digest their mother's milk, most stop after weaning. Some human populations developed a genetic mutation called lactase persistence, allowing them to continue digesting lactose into adulthood.

No, a significant portion of the world's population is lactose intolerant. This is the natural, default human state, with lactase persistence being the exception, not the rule. It is more common in populations with ancestry from northern Europe, where dairy farming was prevalent.

The co-evolution of humans and domesticated animals for milk production drove the spread of the lactase persistence gene. This practice provided a reliable, nutrient-dense food source, especially in areas where other foods were scarce.

When someone with lactase non-persistence consumes dairy, the undigested lactose travels to the large intestine. There, bacteria ferment it, producing gases and acids that cause symptoms like bloating, gas, abdominal pain, and diarrhea.

While bears are omnivores and could theoretically consume dairy, they do not produce sufficient lactase as adults and would likely experience digestive upset. Dairy is not a part of their natural adult diet.

Yes, for human omnivores who are lactose intolerant or choose to avoid dairy, a wide variety of alternatives exist. These include plant-based options like soy, almond, and oat milk, many of which are fortified with essential nutrients like calcium.