Most people in the world are unable to consume cow’s milk and milk products after weaning because they are unable to digest the sugar in milk called lactose. This sugar only exists in mammals’ milk, including human breast milk. In order for lactose to be digested it must be broken down (to glucose and galactose) in the small intestine by the enzyme lactase. Most infants possess the enzyme lactase and can therefore digest lactose, but this ability is lost in many people after weaning, commonly after the age of two. This makes sense as no other mammal consumes milk after weaning. In the absence of lactase, lactose is fermented by bacteria in the large intestine, which leads to a build up of gas. Symptoms of lactose intolerance include nausea, cramps, bloating, wind and diarrhoea and usually appear within two hours of consuming food containing lactose. The symptoms of lactose intolerance and irritable bowel syndrome (IBS) are very similar, so misdiagnosis between the two conditions can occur.
Most infants are born with the ability to digest lactose but over time this ability decreases. There are other, more uncommon, causes of lactose intolerance including injury to the mucus membrane of the small intestine and digestive diseases of the small intestine such as ulcerative colitis and Crohn's disease.
Lactose intolerance varies widely between different ethnic groups:
95 per cent of Asian people
75 per cent of Afro-Caribbean people
50 per cent of Mediterranean people
10 per cent of northern European people
Source NHS Direct, 2005.
Lactose intolerance occurs in as few as just two per cent of some northern European populations and as many as 100 per cent of adult Asian populations (Swagerty et al., 2002). This widespread variation suggests that lactase deficiency is the normal or natural state and that the ability to digest lactose originates from a genetic mutation that provided a selective advantage to populations using dairy products (Swagerty et al., 2002). This idea is supported by William Durham in his book Coevolution (Durham, 1991). Durham describes milk as baby food not ‘intended’ for adult consumption. He describes how the ability to digest lactose is the exception to the norm and can originally be traced back to a minority of pastoral tribes: the Tutsi and Hutu of Rwanda; the Fulani of West Africa; the Sindhi of North India; the Tuareg of West Africa and some European tribes. People who have retained the normal intolerance of lactose include: Chinese, Japanese, Inuit, native Americans, Australian Aborigines, Iranians, Lebanese and many African tribes including the Zulus, Xhosas and Swazis. These people, generally, do not have a history of pastoralism.
In conclusion, drinking cow’s milk is neither normal nor natural. The health implications of being the only mammal to consume milk as adults (and not just that, milk from another species too) are becoming clearer in the scientific literature as levels of the so-called diseases of affluence soar.
The treatment for lactose intolerance is straightforward: avoid lactose. This means cutting out all dairy foods and checking labels for lactose in bread, chocolate and other processed foods.
- What's in milk?
- Milk and Health
- FAQs - Health without milk
- How to be dairy-free
- Viva! Health campaigns