Pulses including soya beans, kidney beans, chick peas, baked beans, broad beans, lentils, peas and calcium-set tofu (soya bean curd) provide a good source of calcium. Other fruit and vegetable sources include parsnips, swede, turnips, lemons, oranges, olives and molasses. A good additional source is calcium-enriched soya milk.
Calcium Uptake and Absorption
The amount of calcium present in a particular food is not the only important factor to consider. The bioavailability of the calcium should be considered when deciding which foods are a good source. This means how much calcium is actually available for absorption into the body from the food. The calcium in dairy products is not as well absorbed as that in many dark green leafy vegetables . For example, calcium absorbability from kale was demonstrated to be considerably higher than that from cow’s milk . While spinach contains a relatively high amount of calcium, it is bound to a substance called oxalate which hinders calcium absorption so it is important to obtain calcium from low-oxalate green vegetables. Grains, nuts and seeds contain a substance called phytic acid which until recently was also considered to hinder calcium absorption, now phytic acid is believed to have only a minor influence (12). Caffeine and smoking have been shown to reduce calcium absorption .Vitamin D
The body requires vitamin D to absorb and retain calcium in the bones. Vitamin D is either obtained from the diet or it is synthesised in the skin following exposure to sunlight. But recent concerns about skin cancer have encouraged us to cover up and avoid the sun. Subsequently people in the UK could be at risk of vitamin D deficiency if they get too little sun exposure year round (14). Without sufficient vitamin D, calcium deficiency is likely to occur even if the diet provides enough calcium. The consequences may be serious, resulting in rickets or osteomalacia (softening of the bones). Over the last few years there have been cases of vitamin D deficiency in some large UK cities (15). Vegans obtain vitamin D from sunlight and fortified foods such as soya milks, cereals and margarines. It is important to get the balance right between being cautious about exposure to the sun and aware of the need for some exposure. It is now advised by the UK government that we apply sun block after 10 to 15 minutes exposure to the sun, this is so that we can synthesise vitamin D in the skin.Magnesium, Potassium, Vitamin C and Vitamin K
Magnesium, potassium, vitamin C and vitamin K are all required for good bone health. A healthy diet that includes at least five servings a day of fruit and vegetables should optimise the intake of these and other micronutrients required (16).Animal Protein and Osteoporosis
Bones consist of a thick outer shell and a strong inner mesh filled with a protein called collagen, calcium salts and other minerals. Osteoporosis (meaning porous bones) occurs when calcium is lost from the bones and they become more fragile and prone to fracture. This debilitating condition tends to occur mostly in post menopausal women due to a lack of the hormone oestrogen, which helps to regulate the incorporation of calcium into the bones. Osteoporosis tends to occur mostly among postmenopausal women aged between 51 and 75. It can occur earlier, or later and not all women are at equal risk of developing osteoporosis.Osteoporosis is sometimes called the silent disease as there are often no symptoms until a fracture occurs. Although the whole skeleton is usually affected fractures mostly occur in the wrist, spine and hip. One in two women and one in five men in the UK will suffer a fracture after the age of 50; in fact every three minutes someone has a fracture due to osteoporosis (17). However, osteoporosis has been diagnosed in people as young as 20. The dairy industry has responded to this health scare by promoting the consumption of milk, cheese and yogurt directly to teenage girls.
However, American women are among the biggest consumers of calcium in the world yet they have one of the highest levels of osteoporosis African Bantu women, on the other hand, eat almost no dairy products at all; they have a relatively low calcium intake, mainly from vegetable sources, and typically have up to 10 children each. Yet osteoporosis is virtually unknown among Bantu women.
It seems that the more dairy produce we consume, the higher our risk of fracture. The Harvard Nurses Health study examined whether higher intakes of milk can reduce the risk of osteoporotic fractures. The study observed over 75000 women for 12 years and concluded that increasing milk consumption did not confer a protective effect against hip or forearm fracture. In fact the report suggested that an increased calcium intake from dairy foods was associated with a higher risk of fracture .
It has been suggested that calcium loss from the bone is promoted by a high intake of animal protein. One study of 1600 older women examined the level of bone loss and found vegetarians had only 18 per cent less bone mineral compared to omnivores who had lost 35 per cent bone mineral by the age of 80 (21). Another study of 1035 elderly women found that women with a high ratio of animal to vegetable protein intake had a greater risk of hip fracture than those with a low ratio ). In a similar study that analysed the incidence of hip fracture in relation to the consumption of animal and vegetable protein in 33 countries it was concluded that moderating the consumption of animal food might protect against hip fracture. Cross-cultural studies summarising data on protein intake and fracture rates from 16 countries compared industrialised and non-industrialised lifestyles and revealed strong links between a high animal protein diet, bone degeneration and the occurrence of hip fractures (24). In Professor T. Colin Campbell’s extensive ‘China Study’ (the largest study in the world of the effects of diet on health) Campbell observed that in rural communities where animal protein made up just 10 per cent of the total protein intake (the other 90 per cent coming from plant-based sources) the bone fracture rate was one-fifth of that in the US where a much higher ratio of animal to vegetable protein is consumed , again indicating a link between animal protein and bone degeneration.
But what is the mechanism for this process?
As food is digested acids are released into the blood, the body attempts to neutralise the acid by drawing calcium from the bones. This calcium is then excreted in the urine (the calciuric response). Animal protein has a particularly bad effect because of the greater amount of sulphur-containing amino acids it contains compared to plant protein. As the sulphur content of the diet increases so does the level of calcium in the urine. Studies reveal that an animal protein diet (with the same total quantity of protein as a vegetarian diet) confers an increased risk for uric acid stones (26). Furthermore the animal-protein induced calciuric response may be a risk factor for the development of osteoporosis. The traditional Inuit (or Eskimo) diet is made up almost entirely of animal protein. Inuits potentially have one of the highest calcium intakes in the world (up to 2,500 mg a day) depending on whether they eat whole fish, including the bones, or not. They also have a high rate of osteoporosis, even higher than white Americans. (27, 28, 29).There are many factors linked to bone health that may even be more important than calcium. For example, when the bone density of 80 young women was monitored over a 10-year period, it showed that exercise was more important than calcium intake (30). In older people, a 15-year investigation into whether low calcium intake was a risk factor for hip fractures concluded that cutting back on dairy did not increase the risk and that physical activity provided better protection (31). The discovery of 18th-century human bones under a London church revealed that today’s women lose far more calcium than our ancestors (32). This may be attributed to a lower degree of physical activity. This research supports an increasing amount of evidence that physical activity is a key factor in reducing osteoporosis risk.
To promote bone health and reduce the risk of osteoporosis it is important to get enough vitamin D, reduce caffeine and alcohol intake and not smoke. Many studies suggest exercise is the most important determining factor. The best type of activity for bone health is weight bearing exercise; this includes walking, stair climbing and dancing.
Summary
- Children and young adults do not need dairy foods for good bone health; they do need exercise and a healthy plant-based diet to ensure strong bones.
- Diets loaded with dairy products are associated with an increased risk of many diseases including osteoporosis, cancer, heart disease, obesity and diabetes.
- From a health perspective, dairy foods should be avoided in the diet.
- Cow’s milk is not a natural food for humans to consume.
- Most people in the world cannot digest the sugar in milk lactose, and are known as lactose intolerant. Therefore, the vast majority of people obtain calcium from plant-based sources.
- Many children are affected by cow’s milk allergies.
- Looking solely at calcium intake and not at calcium losses tells only half the story, while a vegan’s intake might be less than a meat eater’s, their losses are likely to be much lower. A plant-based diet free of animal products - a vegan diet – does not produce these losses.
- There are no scientific reports of calcium deficiency in adult vegans.
- Vitamin D, magnesium, potassium, vitamin C and vitamin K are all required for good bone health.
- Plant-based sources of calcium are many and varied and offer many other health benefits as well as providing a natural and safe source of calcium.
(published with permission in writing from:http://www.vegetarian.org.uk)
