PART TWO: DAIRY CONSUMPTION AND HEALTH
The suggestion that the consumption of cow’s milk can lead to a wide range of health problems, illnesses and diseases strikes at the core of many people’s thinking. How can such a natural food be unhealthy? Well the answer lies in the question; milk is not a natural drink for adults. Furthermore, cow’s milk is not a natural drink for humans. In nature, milk is consumed from a mother up until weaning, which is when the mother normally stops producing milk. Consuming milk from a pregnant mother is not the normal course of events. Furthermore, in nature, mammals consume the milk of their own species, not that of another. In a commentary published in the Journal of the American Academy of Dermatology, New Hampshire dermatologist Dr F.W. Danby states that the human consumption of large volumes of another species’ milk, especially when that milk comes from pregnant cows during the human’s normally post-weaned years, is essentially unnatural (Danby, 2005).
As previously stated, cow’s milk is designed to help a small calf grow into a big cow in less than a year. In order to sustain this rapid physical growth, the composition of cow’s milk has evolved to contain the specific types of nutrients required, at the specific levels required. These are not necessarily natural or healthy for humans. For example, whole milk and certain dairy products such as butter and cheese, contain considerable amounts of saturated fat, cholesterol and animal protein, the detrimental health effects of which are now well-documented. In addition to this, the vitamin and mineral content of cow’s milk is not well-suited to human requirements, especially those of the human infant. To meet the rapid skeletal growth requirements of a calf, cow’s milk contains four times the amount of calcium as human milk. This does not mean that cow’s milk is a good source of calcium for the human infant, far from it; this level of calcium coupled to the high levels of other minerals in cow’s milk represents what is called a high renal solute load which means that the young human infant’s kidneys cannot cope with ‘off the shelf’ cow’s milk.
In addition to the unsuitable nutritional composition of cow’s milk, there are many other reasons why cow’s milk and dairy products are not natural foods for humans, for example, the increasing body of evidence linking bioactive molecules in milk (hormones and growth factors) to disease. While the dairy industry would have us believe that milk is an essential part of the diet, much of the research used to promote this view is industry-sponsored. Furthermore, given that around 70 per cent of people in the world do not drink milk, just how essential can it be? The list of illnesses and diseases associated with the consumption of milk and dairy products is quite extensive. These health problems tend to occur at levels that relate directly to how much milk is drunk in a particular region or country. Furthermore, as milk consumption spreads to areas where previously it was not drunk, these diseases follow. Some of these problems are discussed in detail below.
Acne is a skin condition that affects many teenagers and in a small number of cases it may occur in adulthood. About 80 per cent of people will have some degree of acne between the ages of 11 and 30 (NHS Direct, 2005). Acne can be a very serious problem causing distress and depression in some sufferers who report feeling suicidal because of bullying or lack of self-confidence.
Acne is caused by a combination of factors. Hormonal changes can increase the secretion of an oily substance called sebum from the skin’s sebaceous glands which are frequently located adjacent to hair follicles. If skin cells build up and block the opening of hair follicles, subsequent clogging of the sebaceous gland can contribute further to the development of acne. The problem is often made even worse by the colonisation of the skin by the bacterium Propionibacterium acnes which can become trapped in the hair follicles. Inflammation then may lead to the eruption of large pus-filled spots characteristic of acne. Acne tends to occur on the face, upper arms, upper back and chest.
In general doctors tend to dismiss the possibility of a causal link between the diet and the incidence of acne. However, a large body of scientific evidence now supports such a link. A recent review published in the US journal Seminars in Cutaneous Medicine and Surgery linked diet (either directly or indirectly) to these principal causes of acne (Cordain, 2005). Further to this, a study of 47 acne patients confirmed a causal link between diet and acne. Results suggest that refined grains, sugars, potatoes, processed foods, milk, yogurt and ice-cream together with diets characterised by a high omega-6 to omega-3 fatty acid ratio underlie the development of acne. In these dietary intervention tests all dairy foods, virtually all processed foods, refined grains and sugar were eliminated from the diet which was then comprised primarily of lean meats, fish, fresh fruits and vegetables. Subjects who followed this diet showed immediate improvement in symptoms and eventually became completely clear of acne. The results of this year long experiment will be published in a series of papers in the next year (Cordain, 2005a).
A report linking teenage acne directly to the consumption of dairy foods was published in the Journal of theAmerican Academy of Dermatology in 2005 (Adebamowo, 2005). A link between the intake of milk during adolescence and the incidence of acne was observed in 47,355 women who completed questionnaires on high school diet and teenage acne (as diagnosed by a doctor). Because the link between teenage acne and milk consumption was strongest for skimmed milk, it would seem that the saturated fat content of milk is not the causal factor. The authors hypothesise that the hormonal content of milk may be responsible for causing acne in teenagers. Cow’s milk contains the hormones oestrogen and progesterone along with certain hormone precursors (androstenedione, dehydroepiandrosterone-sulphate, and 5ª-reduced steroids like 5ª-androstanedione, 5ª-pregnanedione and dihydrotestosterone), some of which have been implicated in the development of acne. The levels of these hormones in cow’s milk vary depending on whether the cow is pregnant or not, and if so at what stage of the pregnancy she is. At least two-thirds of cow’s milk in the UK is taken from pregnant cows (Danby, 2005).
Milk also contains bioactive molecules that act on the sebaceous glands and hair follicles (such as glucocorticoids, IGF-1, transforming growth factor-ß (TGF-ß), neutral thyrotropin-releasing hormone-like peptides, and opiate-like compounds), some of which survive pasteurisation. The bioavailability of the factors involved may be altered during pasteurisation. In other words, heat-induced changes in the shape or structure of the molecule may alter the way it behaves in the body and, until we know more, it is difficult to say exactly what role these bioactive molecules play in causing acne and other health problems.
The body’s immune system has to constantly discriminate between many different unfamiliar molecules, some of which may be toxic substances while others are harmless components of food. An allergy results from an inappropriate immune response to such a substance (or allergen) such as dust, pollen or a component of food. An allergic reaction occurs as the body attempts to launch an attack against the foreign ‘invader’ perceived to be a threat to health. In such an attack, the body releases a substance called histamine, which dilates and increases the permeability of the small blood vessels. This results in a range of symptoms including local inflammation, sneezing, runny nose, itchy eyes and so on. These types of reactions may give rise to the so-called classic allergies: asthma, eczema, hay fever and urticaria (skin rash). These responses are called anaphylactic reactions and they vary widely in their severity. The most severe type of reaction (anaphylactic shock) may involve difficulty in breathing, a drop in blood pressure and ultimately heart failure and death.
Initial sensitisation to the allergen precedes an allergic reaction and this first exposure may not generate any perceivable symptoms. In fact initial sensitisation may result not from the direct exposure to an allergen but from exposure to dietary allergens during breast feeding. Evidence suggests that this process, known as atopic sensitisation, can occur in exclusively breast fed infants whose mother’s breast milk contains dietary allergens. For example, a Finnish study reported that a maternal diet rich in saturated fat during breast feeding might be a risk factor underlying the later development of allergies (Hoppu et al., 2000). More recently the same research group reported that breast milk rich in saturated fat and low in omega-3 fatty acids might be a risk factor for eczema (Hoppu et al., 2005). While numerous studies now show that breast feeding can protect against the development of allergies, and the majority of studies are strongly in favour of breast feeding, it may be prudent to avoid suspected allergens in the diet while breast feeding especially if allergies such as asthma, eczema and hay fever run in the family.
Allergies are now so common in the UK, affecting around one in three people, that the increasing occurrence is referred to by some as an epidemic (Royal College of Physicians, 2003). Food allergy is increasingly widespread and the most common of these is cow’s milk allergy, affecting around two per cent of all 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.
Asthma is a chronic, inflammatory lung disease characterised by recurrent breathing problems. Asthma is a common condition that affects around one in eight children and one in 13 adults in the UK (NHS Direct, 2005). The number of children with asthma has risen steeply over the last decade; in the 1970s just one in 50 children had asthma. During an asthma attack, the lining of the airways becomes inflamed and the airways become narrower causing the characteristic symptoms of asthma: coughing, wheezing, difficulty in breathing and tightness across the chest. Asthma can start at any age and the causes are thought to include a combination of factors including a genetic predisposition (asthma in the family), diet and environmental triggers such as cigarette smoke, chemicals and dust mites.
As stated previously, allergies tend to run in families, so asthma, eczema or hay fever in some family members may increase the risk of others developing the same or another allergy. But a genetic predisposition is not the only cause, as stated asthma is caused by a combination of factors. In the past, the rise in childhood asthma has been attributed to an increase in air pollution. However, this seems unlikely as many of the most polluted countries in the world, such as China, have low rates of asthma, whereas countries with very good air quality, such as New Zealand, have high rates of asthma (ISAAC, 1998). The ‘hygiene hypothesis’ has gained popularity as a causal factor for the increase in asthma. This hypothesis blames the increasing asthma rates on the extreme levels of cleanliness found in many homes. Increased hygiene means that our immune systems are being challenged less and less. It has been suggested that this causes us to overreact to allergens such as dust mites.
It has been estimated that food allergies are responsible for approximately five per cent of all asthma cases (James et al., 1994) and as cow’s milk is a primary cause of food allergies, it may therefore be useful to consider the possibility of cow’s milk allergy in the treatment of asthma.
Cow’s milk allergy is a risk factor for many allergic conditions including asthma and eczema (Saarinen, 2005). There is an increasing amount of interest in the role of the diet in the development of eczema. Over the last decade, the links between certain foods and eczema has become better understood. Eczema can be caused by several environmental factors including dust mites, grasses and pollens, stress and certain foods. It is thought that in about 30 per cent of children with eczema, food may be a trigger, and in a smaller group (about 10 per cent), food is the main trigger (National Eczema Society, 2003). The most common foods linked to eczema are cow’s milk and eggs, other foods associated include soya, wheat, fish and nuts (National Eczema Society, 2003).
Hay fever (seasonal allergic rhinitis) is an allergic reaction to grass or hay pollens. A minority of cases may be caused by later flowering weeds or fungal spores, and some research suggests pollution can worsen symptoms. In response to exposure to pollen, the immune system releases histamine which gives rise to a range of symptoms including a runny nose, sneezing and itchy eyes and throat. Again, you are more likely to get hay fever if there is a history of allergies in the family, particularly asthma or eczema (NHS Direct, 2005). Some evidence suggests that altering the diet can help some people with asthma and allergic rhinitis (Ogle and Bullock, 1980). However, the effects of diet on hay fever symptoms have not yet been well studied.
As stated previously cow’s milk-induced gastrointestinal bleeding as an allergic response is a well-recognised cause of rectal bleeding in infancy (Willetts et al., 1999). One of the main causes of gastrointestinal bleeding is dietary protein allergy, the most common cause of which is cow’s milk protein (casein). Gastrointestinal bleeding from milk allergy often occurs in such small quantities that the blood loss is not detected visually, but over prolonged time these losses can cause iron-deficiency anaemia in children. In one trial of 52 infants, 31 of whom had been breast fed, and 21 fed formulas up to the age of 168 days of age, the introduction of cow’s milk (rather than formula milk) was associated with an increased blood loss from the intestinal tract and a nutritionally important loss of iron (Ziegler et al., 1990).
Frank Oski, former paediatrics director at Johns Hopkins School of Medicine, estimates that half the iron-deficiency in infants in the US results from cow’s milk-induced gastrointestinal bleeding (Oski, 1996). This represents a staggering figure since more than 15 per cent of US infants under the age of two suffer from iron-deficiency anaemia.
The only reliable treatment for cow’s milk allergy is to avoid all cow’s milk and dairy products such as cheese, yogurt, butter and cream. Also products with hidden milk content should be avoided, these include products labelled as skimmed milk or skimmed milk powder, milk solids, non-fat milk solids, milk sugar, whey and casein. Casein is difficult to avoid as it is commonly used in the production of bread, processed cereals, instant soups, margarine, salad dressings, sweets and cake mix. Calcium-enriched soya, rice and oat milks can be used as alternatives to cow’s milk. (For other gastrointestinal problems associated with cow’s milk see Lactose intolerance).