Boning up on calcium!
Most people in developed countries have been brought up to believe that our teeth and our bones can only grow healthily if we drink cow’s milk. Over the last three decades we have witnessed a barrage of marketing campaigns designed to reinforce the idea that only milk can supply calcium in sufficient quantities to help us grow big and strong. But is milk really good for you? An increasing amount of research challenges the outdated notion that cow’s milk is best and in fact shows that our consumption of dairy products is doing us much more harm than good.What is Calcium and Why Do We Need It?
Calcium is a soft grey metallic element. It is the fifth most abundant element on the earth’s crust and occurs in compounds such as limestone, chalk and marble. Calcium is required for normal growth and development in animals. It is the most abundant mineral in the human body accounting for around two per cent of the total body weight. Calcium plays an important structural role in maintaining bone health and strength, in fact around 99 per cent of our calcium is deposited in the bones and teeth. The other one per cent is responsible for a range of important metabolic functions that regulate muscle contraction, heart beat, blood clotting and functioning of the nervous system.How Much Calcium Do We Need?
There is no international consensus on what the healthiest or safest amount of calcium we need is. In the UK, the reference nutrient intake value (RNI) is used; this is similar to the Recommended Daily Amount (RDA) used previously. The RNI value for a nutrient is the amount of that nutrient that is sufficient for 97.5 per cent of the people in a given group. The UK government currently suggests that the RNI value for calcium in adults aged between 19 and 50 years of age is 700 mg per day (1). In the US, the recommended daily intake is slightly higher at 1000mg per day (2). However, in many countries such as India, China, Japan, Gambia and Peru the average daily intake of calcium can be as low as 300 mg.Where Do We Get It?
The body obtains calcium in two ways, either from our diet or our bones. When the diet does not provide sufficient levels, calcium is ‘borrowed’ (reabsorbed) from the bones in order to restore blood levels and maintain calcium-dependent biological functions. Calcium in our bones is reabsorbed and replaced continuously as old bone cells break down and new ones form. If adequate calcium is then supplied in the diet, bone levels are restored, but if the diet fails to supply enough calcium, bone loss persists.Children, Young Adults and Bone Health
The idea that cow’s milk is the best source of calcium is deeply entrenched in the British psyche and is sustained by the government-sponsored dairy industry and Milk Development Council who work with schools, dairies and LEAs to encourage more children to drink milk at school. However, a recent review on dairy products and bone health published in the official journal of the American Academy of Pediatrics challenged this misleading notion by concluding that there is very little evidence to support increasing the consumption of dairy products in children and young adults in order to promote bone health. This review examined the effects of dairy products and total dietary calcium on bone integrity in children and young adults and found that out of 37 studies, 27 showed no relationship between dairy or dietary calcium intake and measures of bone health. In the remaining studies the effects on bone health were either small or results were confounded by the fortification of milk with vitamin D. An increasing amount of evidence now suggests that milk is not the best source of calcium at all and goes further to suggest that our bone health would benefit enormously if we switched to plant-based sources. In addition, research suggests that physical exercise is the most critical factor for maintaining healthy bones, followed by improving the diet and lifestyle; this means eating plenty of fresh fruit and vegetables, and for young adults cutting down on caffeine and avoiding alcohol and smoking.In 2004 the Government’s Food Standards Agency (FSA) looked at sources of calcium in the National Diet and Nutrition Survey and found that only 43 per cent of the mean intake of calcium in adults in the UK comes from milk and milk products (1). So despite the misconceived notion that milk is the best (or only) source of calcium the facts show that a large share of the calcium in our diets is derived from sources other than dairy foods. This is not surprising as most people in the world (around 70 per cent) obtain their calcium from plant-based sources rather than dairy products.
But Milk is a Natural Food… Isn’t It?
Humans are mammals, and as with all mammals, we are designed to drink the milk of our mothers until we are weaned onto solid foods. We are the only mammals that continue to drink milk after weaning, and not just that, we are the only mammals to drink the milk of another species (apart from pets that we control). To state the obvious (but often overlooked fact) cow’s milk has evolved to help turn a small calf into a cow in less than a year. That’s why cow’s milk contains around four times as much calcium as human milk; 118mg per 100g compared to 34mg per 100g respectively (4). This discrepancy is for a good reason; calves need a huge amount of calcium to promote the massive level of skeletal growth required over the first year of life. A human infant does not require such high levels of calcium; indeed the high mineral content of cow’s milk puts a strain on the human infant kidney which is why most governments recommend children do not drink cow’s milk in their first year. Indeed the mineral content of cow’s milk is so out of balance with human biochemistry that it is difficult for human adults to absorb the optimum amounts required for healthLactose Intolerance
Many people are unable to consume cow’s milk and milk products 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 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). Losing the ability to digest lactose at this age is a clear indication of how humans are not designed to drink milk as adults; it is not a natural food for us. The frequency of lactose intolerance varies from around 90-100 per cent of Asians, 65-70 per cent of Africans, to 10 per cent of Caucasians ). In the absence of lactase, lactose is fermented by bacteria in the large intestine, this leads to a build up of gas. Symptoms of lactose intolerance include nausea, cramps, bloating, wind, and diarrhoea. The treatment is straightforward: avoid lactose. This means cutting out all dairy foods and checking labels for lactose in bread, chocolate and other processed foods. Many lactose intolerant people obtain their calcium from plant-based sources.Allergies
An allergic reaction to cow’s milk is very different to lactose intolerance and can, in extreme circumstances, be fatal. An allergic reaction to milk occurs when the body’s immune system perceives one of the proteins in milk (either whey or casein) as a foreign invader and launches an attack. Symptoms are generally more extreme than in lactose intolerance and include excessive mucus production resulting in a runny nose and blocked ears. More serious symptoms include eczema, colic, diarrhoea, asthma and vomiting. Casein is more difficult to avoid as it is commonly used in the production of bread, processed cereals, instant soups, margarine, salad dressings, sweets and cake mix. People with milk allergies tend to obtain their calcium from plant-based sources.Cow’s Milk and Diabetes
Type I diabetes is an autoimmune disease where the immune system’s ‘soldiers’, known as T-cells, destroy the body’s own insulin-producing beta cells in the pancreas. This type of response is thought to involve a genetic predisposition (diabetes in the family) coupled to an environmental trigger such as cow insulin or casein – both from cow’s milk. Research shows that some infants may be more vulnerable to type I diabetes later in life if exposed to cow's milk formula while very young. A Finnish study of children (with at least one close relative with type I diabetes) examined whether early exposure to insulin in cow’s milk formula increased the risk of type I diabetes. Results showed that infants given cow's milk formula at three months old had immune systems which reacted far more strongly to cow’s insulin This raises concerns that exposure to cow’s insulin plays a role in the autoimmune process leading to type I diabetes.Another environmental trigger in cow’s milk is thought to be a protein called casein Casein is similar in shape to the insulin producing cells in the pancreas. Because the body may see casein as a foreign invader and attack it, it may also start to attack the pancreas cells having confused them for casein; again leading to diabetes.
A review of the clinical evidence suggests that the incidence of type I diabetes is related to the early consumption of cow’s milk; children with type I diabetes were more likely to have been breast-fed for less than three months and to have been exposed to cow’s milk protein before four months of age (9). The avoidance of cow’s milk during the first few months of life may reduce the risk of type I diabetes. Infants who cannot breastfeed from their mothers would benefit more from taking a plant-based formula such as soya-based formula rather than one based on cow’s milk.
