Lactose intolerance

dr Justine Butler, senior researcher and writer

for article references please email: info@ networkhealth group.co.uk

dr Justine Butler is a Senior researcher and Writer at Viva!Health. Justine holds a Phd in molecular Biology, BSc Biochemistry and diploma in Nutrition. She has published an extensive list of reports, guides and factsheets for Viva!Health and written many articles for health journals, regional and national press.

rethiNKiNG CoWS’ miLK: iS it reALLY Good for US?

This article looks at the history of milk consumption, evolution and lactose intolerance. The links between dairy and a range of other illnesses are examined along with the role cows’ milk in bone health.

Milk is frequently referred to as a fundamental component of a healthy diet. Why is this? Is milk the only source of some essential nutrient, or is milk unique in that it contains all the nutrients that we require? No other animal on the planet continues to drink milk beyond weaning and, not just that, drinking milk taken from another species that is often pregnant. This unusual practise has become a concern for some scientists.

tHe origins of dairy farMing Sheep, cattle and goats were domesticated in parts of the Middle East and central Asia over 9,000 years ago, but it is thought that the use of animals for milk was not practiced until between 6,000 to 8,000 years ago in Asia Minor or Turkey (1). Although this sounds like a long time ago, in evolutionary terms it is very recent history. Hominid (modern human) fossils date back to nearly seven million years ago. If this is represented as a 12-hour clock, starting at midday, humans would have started dairy farming less than one minute before midnight!

dairy farMing today Like humans, cows don’t produce milk unless they have recently given birth. However, the modern dairy cow is routinely impregnated whilst she is still producing milk (this ensures that the milk yield is kept high). At least twothirds of cows’ milk in the UK is taken from pregnant cows (2). This inevitably affects the levels of hormones found in milk. There are 35 hormones and 11 growth factors in milk (3). Some scientists are particularly concerned about the oestrogen content of cows’ milk (4), suggesting that cows’ milk is one of the important routes of human exposure to oestrogens.

Milk production is big business, estimated to be worth £3.8 billion in the UK (5). Although the numbers of dairy cows in the UK have fallen year by year, the milk yield has continued to rise. Over the last 10 years, selective breeding and high protein feed has increased the yield per cow from just under 18 litres per day to over 20 litres per day. The increase in milk yield far offsets the fall in the number of dairy cattle (6). There is a clear trend; fewer cows are being forced to produce more milk, what the cost is to human health remains to be seen.

wHat Lies BeneatH…? The composition of mammalian milk reflects the requirements of the species producing it, be it buffalo, badger, dog or rat - the best milk for them is that of their own species. While whole cows’ milk contains four percent fat, milk from the grey seal contains over 50 percent fat because seals need a lot of body fat to survive in cold water (7). Whole cows’

Food allergy is increasingly widespread and the most common of these is cows’ milk allergy, affecting around two percent of infants under the age of one.

milk contains nearly a third more saturated fat, twice as much protein and four times as much calcium as human milk which makes it ideal fuel for the rapid growth of new born calves. Human babies grow much slower, but brain development is rapid, so breast milk contains five times as much polyunsaturated fat as cows’ milk. Milk also carries important chemical ‘messenger’ molecules that instruct the infant’s immune systems. These features have evolved over thousands of years and are vital in terms of health and disease. Some of the consequences of consuming cows’ milk (and, therefore, signalling hormones) with a nutrient balance not well-suited to human biochemistry are only just becoming apparent.

aCne Despite the general dismissal of diet as a possible factor underlying the development of acne, a substantial body of evidence demonstrates how certain foods (especially cows’ milk) may adversely influence hormones and cytokines that influence the causes of acne (8). Research suggests that the hormones in milk (or components of milk that increase hormone levels) can indeed cause acne in some people (9, 10, 11). Whey protein supplements, favoured by bodybuilders, have also been found to increase the risk of acne (12, 13). Because of this, when taking history from teenage males suffering with acne, the use of whey protein supplements should be screened for.

aLLergies Food allergy is increasingly widespread and the most common of these is cows’ milk allergy, affecting around two percent of infants under the age of one. Symptoms include excessive mucus production resulting in a runny nose and blocked ears. More serious symptoms include asthma, eczema, colic, diarrhoea and vomiting. Food allergies cause around five percent of all asthma cases (14) and 10 percent of eczema cases (15). The most common foods that trigger allergies are cows’ milk and eggs (16). A hypersensitivity reaction to milk proteins can also cause gastrointestinal bleeding in infants (17). This can lead to iron deficiency anaemia in infants and young children. Cows’ milk-induced gastrointestinal bleeding affects about 40 percent of otherwise healthy infants (18). The only reliable treatment for cows’ milk allergy is to avoid all exposure to cows’ milk proteins. This means avoiding all cows’ milk and dairy products, including: milk, milk powder, milk drinks, cheese, butter, margarine, yoghurt, cream and ice cream.

artHritis The possible effects of diet on the symptoms of arthritis are often overlooked too. While certain foods, such as milk products and food colouring (19), may make the symptoms of rheumatoid arthritis worse for some people, a vegan diet may help, possibly because of the types of polyunsaturated fats included in the diet (20). Indeed, both gluten-free and low-fat vegan diets have been shown to help combat the symptoms of arthritis (21, 22). Chemicals called sulforaphanes (found in cruciferous vegetables such as broccoli, Brussels sprouts or cabbage) have anti-inflammatory properties that could help protect against the cartilage damage that occurs in osteoarthritis (23). These effects are certainly worth investigating, but more research is needed to confirm the preliminary findings.

Bone HeaLtH In their recommendations for preventing osteoporosis the World Health Organisation (WHO) state that: ‘The paradox (that hip fracture rates are higher in developed countries where calcium intake is higher than in developing countries where calcium intake is lower) clearly calls for an explanation. To date, the accumulated data indicates that the adverse effect of protein, in particular animal (but not vegetable) protein,

. . . most studies of fracture risk provide little or no evidence that milk and dairy products benefit bone health. Some evidence suggests that dairy products can actually increase the risk of bone fracture.

might outweigh the positive effect of calcium intake on calcium balance.’ (24).

This makes the recommending of milk and especially cheese a somewhat controversial area that some scientists are beginning to challenge. Osteoporotic fracture rates are highest in countries that consume the most dairy, calcium and animal protein (25). In fact, most studies of fracture risk provide little or no evidence that milk and dairy products benefit bone health. Some evidence suggests that dairy products can actually increase the risk of bone fracture (26, 27). So it can be argued that milk is not the best source of calcium and our bone health might benefit if we switch to plant-based sources. Professor Amy Lanou, Chair and Associate Professor of Health and Wellness for the University of North Carolina Asheville, says that bones are better served by attending to calcium balance and focusing efforts on increasing fruit and vegetable intakes, limiting animal protein, exercising regularly, getting adequate sunshine or supplemental vitamin D and getting 500mg of calcium per day from plant sources (25).

In a paper in The British Medical Journal, Lanou says that it is time to revise our calcium recommendations for young people and change our assumptions about the role of calcium, milk and other dairy products in the bone health of children and adolescents. Lanou argues that while the policy experts work on revising recommendations, doctors and other health professionals should encourage children to spend time in active play or sports and to consume a nutritious diet made from whole plant-based foods to achieve and maintain a healthy weight and build strong bones (28).

CroHn’s disease It has been proposed that the pathogenic bacterium that causes Johne’s disease in cattle, Mycobacterium avium subspecies paratuberculosis (MAP), may also lead to Crohn’s disease in humans. MAP infection is widespread among cattle and is also found in retail pasteurised cows’ milk (29). Infection may occur from inhaling MAP in fine water spray from rivers contaminated with infected cow manure. This could explain the clusters of Crohn’s that occur around cities with rivers running through them, like Cardiff in Wales (30) and Winnipeg in Minnesota (31). MAP can be difficult to detect in humans, but when appropriate methods are used, most people with Crohn’s disease are found to be infected (32). Professor John Hermon-Taylor at St George’s Hospital Medical School in London has found MAP in patients with Crohn’s disease from the UK, Ireland, US, Germany and United Arab Emirates (29). Avoiding dairy products alone may not be enough to ensure avoiding exposure to MAP, although if everyone reduced their intake of animal products, there would be fewer cattle and, therefore, less MAP present in the environment.

LaCtose intoLeranCe In 1836, after returning from the Beagle, Charles Darwin wrote: ‘I have had a bad spell. Vomiting every day for eleven days, and some days after every meal.’ Darwin suffered for over 40 years from long bouts of vomiting, stomach cramps, headaches, severe tiredness, skin problems and depression. A number of researchers now think that he may have suffered from lactose intolerance (32). This condition is often overlooked or mistaken for something else.

Professor William H Durham, Professor in Human Biology at Stanford University describes how most North Americans (and indeed most Europeans) are surprised to learn that the majority of the world’s population is unable to digest cows’ milk (33). Durham describes how we live in a culture strongly committed to the concept that cows’ milk is an ideal food; we tend to think of adult milk consumption as normal and healthy. The dairy industry invests much time and money reinforcing this view. In the 1970s this ‘nutritional

The obvious treatment for lactose intolerance is to avoid all cows’ milk and dairy products.

ethnocentrism’ resulted in milk powder being sent abroad as food aid to places where the local population could not digest it. The intended beneficiaries were forced to find other uses for the milk powder; so it was used in whitewash for buildings and distributed in small amounts to be used as a laxative (33). Sadly, in those who could not digest the milk, it disrupted normal digestion and actually increased malnutrition.

wHo Has tHe wHite stuff? Overall, around 70 percent of the world’s population is lactose intolerant (34, 35). At around the age of two (around the time of weaning), most people stop producing the enzyme lactase and so lose the ability to digest lactose, the sugar in milk. As stated, lactase persistence only developed around 8,000 years ago. In evolutionary terms, this is very recent history.

The ability to digest lactose can be traced back to a minority of pastoral tribes who gained a selective advantage from the genetic mutation that enabled persistent lactase (36). This includes 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 (33). Descendants of these people are able to consume dairy milk today without suffering the symptoms of lactose intolerance (bloating, wind, discomfort etc). In Northern Europe, the prevalence of lactose intolerance is relatively low, varying between one to18 percent (37). The highest levels of milk consumption in the world are seen in Finland, Sweden, the Netherlands, Albania, Germany and Norway.

Lactose intolerance is most prevalent in Asian and African countries with 80 to 100 percent frequency in some cases. People who have retained the normal intolerance of lactose include the 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 and many don’t consume any milk products at all. The lowest rates of milk consumption in the world are seen in Thailand, Vietnam, the Democratic People’s Republic of Korea, Mozambique, the Congo and Liberia (38). It could be argued that the lower level of consumption seen in some developing countries reflects the fact that people can’t afford to buy milk products. However, in Japan, which is not a developing country, consumption is very low. Whether the reason is cultural, economic, historical or biological (lactose intolerance), the fact remains that most people in the world don’t drink milk. The obvious treatment for lactose intolerance is to avoid all cows’ milk and dairy products. This means checking labels for lactose in bread, chocolate and other processed foods including meats. In addition, lactose is used in some types of medication, so patients should check with their GP or pharmacist (although symptoms of lactose intolerance rarely occur as a result of taking medication containing it). An increasing amount of lactose-free products are appearing to cater for the lactose intolerant and boost sales of dairy foods. Plant-based milks (soya and nut milks) are naturally lactose-free. Although there is no evidence of calcium deficiency in people eating a diet with no lactose (39), patients cutting out dairy foods may need some help and advice on how to ensure that they still get plenty of calcium. This may be important for young children who need calcium for healthy growth and development. In conclusion, it can be argued that cows’ 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 and may soon force the government to reconsider how cows’ milk and dairy products are promoted. This article presents a summary of an extensive fully-referenced scientific report called White Lies. All the facts presented are based on peer-reviewed published research. To find out more or to access the full references, see the full report online at: www.viva.org.uk/resources/ campaign-materials/reports/whitelies