Why are animals lactose intolerant? Almost all mammals are lactose intolerant when they are fully grown, which means that they cannot tolerate milk and dairy products. What is considered an allergy and an exception in humans is normal and natural in adult mammals.
Lactose intolerance in animals: why it's normal
Why can't most mammals tolerate milk?
Yes, it's true, lactose intolerance in animals is normal; almost all mammals are lactose intolerant as soon as they reach adulthood. During the developmental phase of a young mammal, there is a transition period where the animal stops being able to digest lactose as soon as it stops drinking milk regularly. Milk is the only food that contains lactose.
During this transition phase, the production of the enzyme lactase, which is responsible for the breakdown of lactose, is gradually reduced.
Why do adults normally tolerate milk?
LCT, the gene for the enzyme lactase, is actively downgraded in the body as soon as the growing animal replaces milk with other, more substantial foods. The process of this weaning appears to be the trigger for the reduction of the gene.
However, most people do not stop drinking milk as adults. In most people, there is a mutation that allows the LCT gene to remain active in adulthood. So if a person stops consuming any dairy products as an adult, their body is likely to become lactose intolerant.
Why can some cats and dogs drink milk their whole lives?
As the production of lactase is downgraded by weaning, many animals that have never stopped drinking milk retain a limited ability to digest lactose. However, they too can only tolerate small amounts of milk, as the LCT gene is reduced in any case.
What happens when lactose-intolerant animals drink milk?
When an adult mammal drinks milk after weaning, the undigested lactose is passed through the digestive tract. In the process, it draws fluid with it. At the same time, fermentation takes place in the intestine due to the intestinal bacteria, which produces unstable fatty acids. This in turn leads to stomach discomfort, diarrhoea and even vomiting.
Typical symptoms of lactose intolerance
The symptoms of lactose intolerance usually occur within a few hours of consuming food or drink containing lactose.
Common symptoms include
- Flatulence
- Diarrhoea
- a bloated stomach
- Stomach cramps and pain
- Stomach rumbling
- General malaise
The severity of symptoms and when they occur depends on the amount of lactose you have ingested. Some lactose intolerant people can drink a small glass of milk without triggering symptoms, while others may not even be able to have milk in their tea or coffee.
