Dr Justine Butler, Senior Researcher for Viva! Health, explores problems that can arise from having cow’s milk in a diet.
Lactose intolerance and cow’s milk allergy often get mixed up. Lactose intolerance is caused by a lack of an enzyme that helps you to digest the sugar in milk. Cow’s milk allergy, on the other hand, is an adverse immune reaction to proteins found in milk. They are completely unrelated conditions, except that they share a common cause – cow’s milk and dairy products.
After returning from the Beagle expedition in 1836, Charles Darwin wrote: “I have had a bad spell. Vomiting every day for eleven days, and some days after every meal”.
Darwin himself struggled for over 40 years with long bouts of vomiting, stomach cramps, headaches, severe tiredness, skin problems and depression. Researchers now think that he had lactose intolerance and his case is a good example of how easily it can be missed or misdiagnosed.
Lactose is the sugar in mammal’s milk and in order to release its energy, it must be broken down into its constituent simple sugars – glucose and galactose – so they can be absorbed. This task falls to an enzyme called lactase, produced by cells lining our small intestines.
If your body doesn’t produce this enzyme, then lactose travels to the large intestine where it is fermented by gut bacteria, producing hydrogen and a range of potential toxins. This is ‘lactose intolerance’ and most symptoms result from the production of gases and toxins by these gut bacteria.
Symptoms include bloated and painful stomach, wind, diarrhoea and, on some occasions, even nausea and vomiting. Other symptoms can include muscle and joint pain, headaches, dizziness, lethargy, difficulty with short-term memory, mouth ulcers, allergies, irregular heartbeat, sore throat, increased need to pass urine, acne and depression.
Even more worrying for sufferers of lactose intolerance is that the toxins produced by the gut bacteria may also play a key role in diseases such as diabetes, rheumatoid arthritis, multiple sclerosis and some cancers.
Weaned off lactase
Everyone naturally produces lactase when they are babies – without it we couldn’t drink our mother’s milk. However, all mammals and the vast majority of people stop producing it soon after weaning – for us, around the age of two. This is the normal state for most people – around 70 per cent of the world’s population, in fact.
In northern central Europe, lactose intolerance affects between two and 20 per cent of people, rising to 40 per cent in Mediterranean countries – most common in Italy where it affects 56-70 per cent in some regions. Highest rates are seen in Africa, where it affects 65-75 per cent of people, and Asia, where more than 90 per cent of people are lactose intolerant.
So why are some people able to digest lactose after weaning and others not? ‘Lactase persistence’ originates from a genetic mutation that occurred among a small number of European and African pastoral tribes within the last 5,000-10,000 years – in evolutionary terms, this is very recent history. It provided a selective advantage to populations using dairy products, making them more likely to live longer and have children, so the ability to digest lactose was passed on to subsequent generations. Descendants of these people are still able to consume cow’s milk without suffering the symptoms of lactose intolerance. It doesn’t mean, however, that it’s good for them!
The treatment for lactose intolerance is straightforward: avoid lactose. It means cutting out all cow’s milk, and other dairy foods and checking labels as lactose is added to many unlikely foods, including bread, breakfast cereals, salad cream, mayonnaise, biscuits, chocolate, cake, crisps, instant soup and some processed meats, such as sliced ham. The word ‘lactose’ will not necessarily be listed on food labels, so look out for things like dried milk or whey powder.
Lactose is also used as a filler in many medications and, while this may not trigger symptoms in most people with lactose intolerance, it can cause problems in some. Check with your doctor and request lactose-free tablets.
Allergy not intolerance
Cow’s milk allergy is very different to lactose intolerance. An allergic reaction is when the body’s immune system launches an inappropriate response to substances mistakenly perceived as a threat. Common triggers include latex, detergent, dust, pollen or certain proteins in food. In cow’s milk, it is the protein casein that causes most problems, but whey protein can also trigger a reaction in some people.
General symptoms include inflammation, sneezing, runny nose, itchy eyes and so on, giving rise to the classic allergies – asthma, eczema, hay fever and urticaria (skin rash or hives). Because cow’s milk allergy is linked to many conditions – including asthma and eczema – it’s always useful to consider it when treating them.
Cow’s milk allergy is one of the most common food allergies in children, affecting between two and 7.5 per cent of infants under one, although some grow out of it by the age of five. Symptoms include an itchy rash or swelling, stomach ache, vomiting, colic, diarrhoea or constipation and a runny nose. Symptoms can appear almost immediately or up to 72 hours after consuming cow’s milk protein. This makes it difficult to diagnose.
A big problem affecting infants can be gastrointestinal bleeding resulting from cow’s milk allergy. Blood loss often occurs in such small quantities that it goes unnoticed, but over time can cause iron-deficiency anaemia. Scientists suggest that blood loss associated with cow’s milk consumption in infancy may affect 40 per cent of otherwise healthy infants.
Keep away from children
Regardless of these problems, it’s simply not a good idea to give cow’s milk to children, as it contains virtually no iron, but does contain potent inhibitors, reducing the body’s ability to absorb iron from other foods in the diet. The high protein, sodium, potassium, phosphorus and chloride content of cow’s milk present what’s called a ‘high renal solute load’.
Unabsorbed solutes from the diet must be excreted by the kidneys and this can place a strain on immature kidneys, forcing them to draw water from the body, increasing dehydration risk. This is why most health bodies say that cow’s milk should not be given to children under 12 months of age.
Although a lot of food allergies start in childhood, you can develop them as an adult, too. Cow’s milk allergy in adults is relatively rare, but symptoms tend to be much more severe than they are in children when they do occur, with reactions being triggered by amounts as low as 0.3 milligrams of cow’s milk protein.
The most severe type of allergic reaction (anaphylactic shock) may involve difficulty in breathing, a drop in blood pressure and ultimately heart failure and death. Occasionally, cow’s milk allergy can cause severe symptoms that come on suddenly, such as swelling in the mouth or throat, wheezing, coughing, shortness of breath and difficulty breathing. In such cases, immediate medical help should be sought.
Check the label
The only reliable treatment for cow’s milk allergy is to avoid all cow’s milk and dairy products, including milk, milk powder, milky drinks, cheese, butter, margarine, yoghurt, cream and ice cream. Products with hidden milk content should also be avoided – look out for: casein, caseinates, hydrolysed casein, skimmed milk, skimmed milk powder, milk solids, non-fat milk, whey and milk solids.
People with cow’s milk allergy face a similar problem as those avoiding lactose – milk-based ingredients can be difficult to avoid as they are commonly used in the production of so many foods. It can seem a daunting prospect, having to read the ingredients labels, but most supermarkets now produce product ‘free-from’ lists and many have their own-label range. There are even iPhone apps available now to help you identify ingredients by scanning the product barcode. Soya ice creams, spreads and yoghurts and dairy-free cheeses are some ‘free-from’ examples.
For anyone worried about missing out on calcium, there are many excellent non-dairy sources, including green leafy vegetables (spinach is a relatively poor source as it contains oxalate that binds calcium), dried fruits, nuts and seeds, calcium-set tofu and calcium-fortified soya milk. Remember, 70 per cent of the world’s population don’t do dairy – so you’re not alone!
Cow’s milk on the wane
Dairy consumption in the UK is in decline as the market for plant-based milks, vegan cheese, yoghurt and other alternatives is booming. Whether you are lactose intolerant, allergic to cow’s milk protein or simply want to cut out dairy for health reasons, the animals or the environment, there’s never been a better time to go dairy-free.