Boning up on Calcium Why Plant Calcium is Best
By Dr Justine Butler & Veronika Powell MSc Viva! Health Senior Health Campaigners
Most people in developed countries have been brought up to believe that our teeth and our bones can only grow healthily if we drink cows’ milk. Over the last three decades we have witnessed a barrage of marketing campaigns designed to reinforce the idea that only dairy milk can supply calcium in sufficient quantities to help us grow big and strong. But is it really good for you? An increasing amount of research challenges the outdated notion that cows’ milk is best and in fact shows that our consumption of dairy products is doing us much more harm than good.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 in 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, heartbeat, 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 700mg per day (National Diet and Nutrition Survey, 2004). In the US, the recommended daily intake is slightly higher at
1000mg per day (NIH Consensus Statement, 1994). However, in many countries such as India, China, Japan, Gambia and Peru the average daily intake of calcium can be as low as 300mg.
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 or causes calcium leaching from the bones, bone loss persists.
Calcium and Bone Health The idea that cows’ milk is the best source of calcium is deeply entrenched in the British psyche and is sustained by the government-sponsored dairy industry and the Milk Development Council who work with schools, dairies and LEAs to encourage more children to drink milk at school. However, a review of 37 studies 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 no solid evidence that the consumption of dairy products improves bone health in children and young adults (Lanou et al., 2005). Another review of 15 studies on calcium intake and the risk of hip
fractures (Bischoff-Ferrari et al., 2007) suggests that neither total calcium intake nor calcium supplementation is significantly associated with decreased hip fracture risk in women or men. As for calcium supplementation, the authors suggested that it might indeed increase the risk. The latest study of this type brought very similar results (Warensjö et al., 2011). Over 60,000 women were followed for up to 19 years and when the data were analysed, it was found that calcium intake above 750mg didn’t offer any protection from fractures and high calcium intakes increased the risk of hip fractures. Harvard experts (Harvard School of Public Health, 2012) recently
confirmed this when they highlighted that in countries such as India, Japan and Peru where average daily calcium intake is as low as 300 milligrams per day, the incidence of bone fractures is lower than in many western countries (including the UK). An increasing amount of evidence now suggests that cows’ 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, 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. 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 on to 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) cows’ milk has evolved to help turn a small calf into a cow in less than a year. That’s why cows’ milk contains around four times as much calcium as human milk; 118mg per 100g compared to 34mg per 100g respectively (FSA, 2002). 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 cows’ milk puts a strain on the human infant kidney which is why most governments recommend children do not drink cows’ milk in their first year.
Lactose Intolerance Many people are unable to consume cows’ milk and milk products
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