Milk for healthy bones?

Milk for healthy bones

There are some worrying anomalies that are becoming obvious relating to the consumption of dairy foods and the incidence of osteoporosis. In the UK we consume the greatest amount of dairy products in Europe, and yet we also have the worst incidence of osteoporosis. Additionally, if you look at cultures where dairy products are not widely consumed and where they actually have a lower calcium intake than we do, in particular the Far-East, the incidence of this bone disease are particularly low. Something does not add up!

We are suffering an epidemic of bone fractures in the UK amongst post-menopausal women, and the rate of incidence has been increasing steadily this century. The main cause of bone fractures is osteoporosis, or brittle bone disease.

The silent thief

Osteoporosis is a gradual loss of minerals from the matrix of the bones. Eventually the matrix begins to look like a sponge, is weakened, and then crumbles. This is a painful, and often life threatening problem. It has been called the silent thief, because there are no outward visible early warning signs of de-mineralisation. The only way to be forewarned of this problem is to have occasional bone scans. One in three women will suffer from osteoporosis and one in eight men will also succumb.

It is now widely observed that osteoporosis is starting in younger women in their 20s and 30s, and it has also been noted in teenagers – rather than just in post-menopausal women. A study of women’s bones in Spitalfields, in the east-end of London, dating from the early-18th to mid-19th centuries, found that bone density was significantly better than that of women today, both pre- and post-menopausally, despite our supposedly better diet nowadays.

Risk factors

There are many recognised contributory factors to osteoporosis. These include imbalance of hormones (sex and thyroid hormones), lack of weight bearing exercise, smoking, and heavy alcohol and caffeine consumption.

Detailed advice on how to reduce the risk of osteoporosis with dietary measures is rarely offered, despite the weight of evidence on how profoundly diet can influence the development, and the halting of this disease. The usual dietary advice dished out is to make sure that you get sufficient calcium, together with vitamin D to help the absorption of the calcium.

The recommended daily allowance (RDA) for women is 500 mg a day of calcium (or 1200 mg if they are teenagers, pregnant or lactating), and they are usually told that the best way to achieve this is to drink a pint of milk a day, or to get an equivalent amount from other dairy products such as cheese and yoghurt. But is this advice appropriate, and does it work?

This advice can alarm people who have an allergy to milk proteins or who are lactose intolerant. About 10% of adults have these problems, and in some communities, such as Asians, lactose intolerance can soar to around 70%. Many more people feel that dairy products do not ‘agree with them’ and experience partial or complete relief from nasal mucus, migraines, hay fever, asthma or eczema if they avoid dairy products. Where does the advice to drink milk, to avoid osteoporosis, leave them?

Dairy doubts

Many nutritionists have been arguing for a long time that it is simplistic to consider calcium to be the main dietary answer to solving this problem. Bone building is a complex mechanism involving many elements. The minerals calcium, magnesium and phosphorous are required. Zinc is necessary for the growth process, vitamin C is used to manufacture the matrix and vitamin D and boron are needed to help absorb and use calcium.

Of key importance in the body’s ability to use calcium is that it is obtained from a source that is also a good source of magnesium. The balance between these two minerals is essential – without magnesium the body cannot maximise the use of calcium. And of course while dairy products are very dense sources of calcium, they have almost no magnesium. And anyway how do cows grow such large, strong bones after weaning? They eat grass. And here there is a clue… any green leafy vegetable will have the perfect balance of calcium and magnesium, since magnesium is the basis of the ‘green factor’ in plants, chlorophyll. Nuts and seeds also provide this perfect balance of minerals.

The human body can use calcium derived from these sources much more efficiently than from milk and cheese. In fact the saturated fats in whole milk and cheese actually slows down the absorption of calcium into the body. Calcium can be obtained from a variety of sources, as listed in the chart (below??).

But the potential problem with dairy products in relation to bone health is possibly even greater. A World Health Organisation survey has shown that high protein diets, with low vegetable intake, contribute to osteoporosis. High protein diets increase the loss of calcium in the urine. The most extreme example of this is the Eskimos: they are lucky enough to have one of the lowest incidence of heart disease risk due to the high oily fish content of their diet, however they also have the world’s worst osteoporosis problems. Traditionally they subsist on large quantities of fish and seal meat, but have almost no fresh vegetables or fruit.

Excess protein results in an ‘acid’ residue in body tissues. Since the body is principally an alkaline medium, acid residues in cells are positively dangerous. In particular our blood must be kept slightly alkaline, if not this can lead to acidosis, a life threatening condition. The body has a number of ‘buffering’ systems that alkalises any acid residue and these buffering systems all use calcium as a key component of their activity. The principal source of calcium for this activity is calcium that is lodged in the bones. So dairy products, which are protein dense foods, may also contribute to calcium loss in addition to not providing highly usable calcium in the first place.

So what the answer?

So what can be done, from a dietary point of view, to reduce the risk of this disease? Certainly bone is living tissue which replaces itself over the period of about a year, so the potential for bone regeneration is good in pre-menopausal women. It may well be wise to avoid depending too heavily on dairy products especially if other protein dense foods, such as meat, are eaten regularly. A little cheese once in a while will not harm, it is excess that is in question. The calcium in yoghurt is more bio-available than from other dairy sources.

The reason for this is that it is a fermented product and the B-vitamins that the bacteria manufacture help the uptake of calcium. A varied diet that includes a wide selection of green leafy vegetables, nuts and seeds has been shown to be very protective providing a wide range of nutrients that are necessary for bone health. Other factors to limit are high salt intake and high phosphorous intake (from soft drinks and junk foods) both of which contribute to bone loss.

All this advice is appropriate for growing children and at other times of fast bone growth, such as pregnancy. Indeed at these times the body ingeniously increases its ability to absorb calcium from foods. Under normal circumstances we absorb around 20-30% of calcium from our diets, but children and pregnant women will absorb about 75% of dietary calcium. This means that the mechanism is in place to make the best use of our diet… if only we can give our bodies the best diet to make use of.

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