Osteoporosis: the fractured truth

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Osteoporosis. The very word strikes fear into people's hearts, conjuring up images of frail, hunched-over little old ladies with ribs so fragile they can fracture from coughing, and hips that break when they step off a kerb. Women are particularly afraid, and for good reason:

40% of Australian women over fifty will suffer an osteoporosis-related bone fracture during their remaining lifetime

Each year 20,000 Australian women suffer a hip fracture; up to one-fifth of these women die from complications of the fracture within 12 months.

This exceeds the death toll from cervical and uterine cancer combined.

Women are the primary focus of osteoporosis data collection and research, but one in seven older Australian men has some degree of osteoporosis too.

'Calcium' is the first thing most people think of when osteoporosis is mentioned. 'HRT' is probably the second. But the standard view of osteoporosis prevention and treatment is largely founded on myths. Let's examine these myths, and some facts that will make you question what you've been told about this potentially dangerous, unnatural and unnecessary condition.

Myth # 1: Osteoporosis is caused by calcium deficiency.

Open any medical textbook and you will find that osteomalacia - a disorder unrelated to osteoporosis - is the disorder resulting from under-calcification of bones. Whereas bone tissue affected by osteomalacia is of reduced quality because of calcium deficiency, osteoporotic bone is normal in quality but reduced in quantity - of the missing bits, all the minerals as well as the protein matrix that holds those minerals in place have been leached away.

Fact # 1: Osteoporosis is emphatically NOT a calcium deficiency disorder.

Rather, it is an imbalance between the intake/absorption and the excretion of bone-building materials including calcium - a pathological extension of osteopaenia, the normal physiological bone-thinning process that occurs with increasing age.

Myth # 2: A high calcium intake will prevent or cure osteoporosis.

This myth follows from the first one. It fuels the constant bombardment of the public by media advertisements, and admonitions from health and medical professionals, warning us that we must consume prodigious amounts of calcium to avoid developing osteoporosis. Yet study after study has found that calcium intake in adulthood has no correlation with bone density.

In one study, women were given calcium supplements to bring their total daily intake to between 1000 mg and 2000 mg. After two to three years, it was found that those who took calcium supplements had no greater bone density than women who took no calcium supplements.

The Nurses Health Study (reported in the American Journal of Public Health, 1997; 87: 992-997) followed 77,761 US women aged 34 to 59 since 1980, and found that women with higher dietary calcium intakes tended to have a higher risk of hip fracture. And a comparison of hip fracture rates in ten countries also revealed that as calcium intake increased, so did the rate of fracture.

The traditional Inuit (Eskimo) diet contains about 2,000 mg of calcium per day, largely from fish bones, yet the Inuit's rate of osteoporosis-related bone fractures is one of the highest of all population groups. The lowest osteoporosis rates belong to certain African tribespeople, such as the Bantu, who consume only 175 - 475 mg of calcium per day, and the Japanese, whose traditional diet contains under 500 mg per day. Yet women of Oriental origin are considered at higher risk of developing osteoporosis when living in Western societies (because of their lighter bone structure), and when Bantu people migrate to Western countries and adopt the dietary patterns of their new homes, their rates of osteoporosis rise to equal those of their white neighbours.

Fact # 2: There is no evidence that a higher calcium intake in adulthood will prevent or reverse osteoporosis.

Inadequate calcium intake in childhood leads to a lower peak bone mass and may predispose to osteoporosis in later life. (See The Calcium Story below for a discussion of what constitutes an adequate calcium intake.)

Myth # 3: A high intake of dairy products helps protect against osteoporosis.

This myth follows on from Myth # 2 and is equally ill-founded. The Nurses Health Study referred to in Myth # 2 specifically examined dairy intake and osteoporosis, and found no evidence that higher intakes of milk prevented fractures. Asian and African populations, among whom lactose intolerance is the norm and hence dairy-food consumption is minimal or non-existent, have much lower rates of osteoporosis than dairy-consuming populations.

Fact # 3: Table 1 clearly shows that dairy products don't protect against osteoporosis.

Table 1: clearly shows that dairy products don't protect against osteoporosis

Myth # 4: Osteoporosis is an oestrogen-deficiency disease, so hormone replacement therapy (HRT) is an effective therapy for it.

Age-related bone loss begins to occur in people following standard Western dietary and lifestyle patterns, at about 40 years of age. The hip-fracture rate for white women begins a steep climb between 40 and 44, and the rate of climb does not change around the time of menopause, at ages 48 to 51 or later. In a woman's early 40s, her levels of oestrogen (the chief hormone 'replaced' in HRT) have not significantly dropped, although progesterone production is often falling. So it is clear that declining oestrogen levels are not the primary trigger of the bone-thinning process.

Interestingly, women living in Asian and African cultures with low osteoporosis rates, tend to have much lower oestrogen levels throughout their lives than do Western women. They begin menstruating several years later, and go through menopause several years earlier, than Western women. These differences are related to their high physical activity level, low calorie and fat consumption, and high fibre intake, which lead to lower body-fat levels than those of Western women and markedly different bowel flora composition.

Body fat is a major site of oestrogen production and, in addition, the Asian and African women excrete far more oestrogen in their bowel movements than do Western women on high-meat, high-fat diets, whose bowel flora 'recycle' oestrogen that was on its way out of the body, and put it back into circulation. (Incidentally, the higher rate of breast cancer among meat-eating women compared to vegetarians is also thought to be related to differences in body fat levels and bowel flora composition.) Another advantage for women in traditional cultures is that they tend to practise extended breastfeeding (two years or more), which further lowers their lifetime exposure to oestrogen by delaying ovulation.

In Western societies, thin women are considered to be at higher risk of osteoporosis than their plumper sisters, yet slender Asian and African women have lower rates of fracture than Western women with higher body-fat levels and greater lifetime exposures to oestrogen.

The epidemiological evidence shows that having a high oestrogen level does not reduce a woman's risk of osteoporosis and related fracture. There is some speculation, however, that the steepness of the fall in oestrogen level that occurs after menopause, may play a role. This fall is far more pronounced in women who have had higher oestrogen levels throughout their lives, because of the lifestyle factors mentioned above. The fact that women who have had a hysterectomy with oophorectomy (removal of the uterus and ovaries) are at higher than normal risk of osteoporosis, lends support to the 'sudden oestrogen drop' hypothesis.

Long-term use of HRT is recommended by many in the medical fraternity to help prevent osteoporosis, despite the fact that large-scale randomised trials to assess its benefits and risks for this condition only began in the mid 1990s (after it had been widely prescribed for more than 20 years). It is astonishing that a drug with so much potential for harm, can be so widely advocated as a treatment before being properly evaluated. So much for 'evidence-based medicine'! Many medical experts warn that the potential harm may outweigh the benefits.

In the light of this lack of proof that HRT is effective at preventing osteoporosis, it is sobering to consider its roll-call of proven adverse effects: endometrial cancer, high blood pressure, elevated blood sugar, blood clots, abnormal vaginal bleeding, nausea, vomiting, tissue swelling, abdominal bloating, breast swelling and tenderness, changes in bodyweight and libido, headache, depressive moods, back pain and muscle cramps.

Fact # 4: There is no reliable evidence from long-term trials that HRT prevents osteoporosis and related fractures. There is, however, abundant evidence that HRT can cause serious, even life-threatening adverse reactions.

Myth # 5: Bone-density scanning provides the most accurate indication of a person's fracture risk.

An entire medical industry has been built upon bone mineral density (BMD) testing (see Table 2 for descriptions of the various techniques used), working on the assumption that lowered BMD is strongly correlated with an increased risk of bone fracture. However, a recent Canadian government study found that bone thinning is a poor predictor of future fractures. The amount of weight-bearing exercise performed by study subjects predicted their fracture risk far more accurately.

Table 2: Tests to assess bone mineral density (BMD)

Fact # 5: Muscle strength and coordination may be the best predictors of fracture risk, because they reduce the occurrence of falls.

Weight-bearing exercise increases muscle strength and co-ordination, diminishing the probability of falls in which fractures might occur. Medical authorities agree that fractures of the forearm and hip could be virtually eradicated if falls could be prevented.

THE CALCIUM STORY

Calcium balance

As mentioned above, osteoporosis involves the depletion of all bone-building minerals and the protein matrix from bone. Since calcium is the major mineral in bone, however, its metabolism has been studied more thoroughly than that of magnesium, phosphorus, zinc, boron and the other minerals contained in bone. Although the following points refer specifically to calcium, the same mechanisms also affect other vital bone-building nutrients.

Calcium balance refers to the interplay between the intake, absorption and excretion of calcium. Our bodies selectively absorb only a small fraction of the calcium we consume.

We excrete calcium primarily in our urine and faeces. If we absorb more calcium in a day (from food and/or supplements) than we excrete, we will be in 'positive calcium balance.'

If we excrete more than we absorb, 'negative calcium balance' results, and our bones - the major storage site for calcium within the body- will release some of their calcium to top up blood levels. It is not deficient intake of calcium that causes osteoporosis, but rather being in negative calcium balance day after day, year after year.

In 1994 the US Institutes of Health Consensus Development Conference on Optimal Calcium Intake determined that calcium intake accounts for only 10% of the total impact on calcium balance, while absorption accounts for 15% and excretion for 75% of the total impact. Here's what we need to know about each of these three factors:

Intake

The Recommended Daily Intake (RDI) of calcium in Australia is 800 mg for adults, and 1000 mg for postmenopausal females. Yet most of the world's population consumes only 300 - 500 mg of calcium per day, and osteoporosis and fractures in such countries are significantly lower than in Western countries with high daily recommended and actual intakes. Studies of calcium intakes of prisoners in Peru revealed that 200 - 300 mg of calcium daily is enough to maintain metabolic equilibrium, while deliberate experiments to assess calcium balance suggest that only 150 -200 mg is sufficient.

Maintaining an adequate calcium intake is easily accomplished on a diet of fresh and dried fruits, vegetables (especially green leafy vegetables, including sea vegetables like dulse, kelp and nori), nuts, seeds (particularly sesame seeds), whole grains and legumes. A diet based on these foods also contains other minerals and vitamins essential to bone health, in the correct ratios required.

Absorption

Our bodies absorb on average only 20% - 30% of the calcium we consume. The higher the amount of calcium consumed, the lower the percentage absorbed - as low as 15% at the standard Australian RDI of 800 mg per day - and vice versa. During pregnancy and lactation, women absorb significantly more - up to 70%. As we get older, however, decreased production of stomach acid reduces our ability to absorb calcium (and other minerals). Drugs that neutralise stomach acid or inhibit its production lower calcium absorption even further.

Alcohol and the oxalic acid in tea, coffee, chocolate and some other foods reduce calcium absorption.

Some fat must be present in the intestines in order for us to absorb calcium from foods (so skim milk is next to useless as a calcium source).

Raw, unsalted nuts and seeds and avocado are excellent sources of healthy fats that help boost calcium absorption.

The calcium in green leafy vegetables is absorbed about twice as well as the calcium in milk and other dairy products. Table 3 compares how much calcium we absorb from various foods.

Table 3: Compares how much calcium we absorb from various foods.

Exposure to sunlight stimulates the body to produce vitamin D, which increases calcium absorption to the same degree as does oestrogen, without the increased risk of cancer associated with oestrogen supplementation.

Excretion

Factors which increase calcium excretion:

(a) Sedentary lifestyle. Weight-bearing activity is probably the most important factor affecting bone development. When muscles contract in the course of activity, they exert a pull on the bone which causes it to thicken.

Men are seven times less likely than women to suffer clinical effects of osteoporosis, because apart from having heavier bones to begin with, they have larger, stronger muscles which exert more pull on their bones, and they tend to perform more exercise -especially muscle-strengthening exercise - than women in our society.

Disuse of muscles causes rapid weakening of bone; in the weightless environment of space, astronauts suffer profound loss of skeletal mass despite vigorous physical activity.

(b) High protein Intake. As Table 1 shows, daily protein intake, and particularly animal-protein intake, is clearly correlated with fracture risk in different populations.

Plant proteins do not carry the same risk. A British study found that vegetarians aged 70 had bones of equal or greater density compared to meat-eaters aged 50.

A US study, the largest of its kind ever conducted, measured the bone density of vegetarians and non-vegetarians, and found that by the age of 65:

male vegetarians had lost an average of 3% of their bone mass

male non-vegetarians had lost an average of 18%

female vegetarians had lost an average of 7%

female non-vegetarians had lost an average of 35% of their bone mass.

The digestion of proteins - particularly animal proteins because of their high sulphur content - produces extremely acidic breakdown products, generating an 'acid tide' in the bloodstream after a high-protein meal. (Red-meat protein is the most acid-forming, followed by poultry and fish.) To neutralise the acidity, the body calls on its bone stores of alkaline calcium (and to some degree magnesium). The hyperacidity produced by the breakdown of protein decreases the kidneys' ability to reabsorb calcium that they have filtered from the blood, causing excessive loss of calcium in the urine.

Nitrogen-balance studies show that we need less than 40 grams of protein per day, but the average Australian woman consumes as much as 100 grams per day and men usually consume even more.

Yet as little as 75 grams of protein per day, even with a daily calcium intake of 1400 mg, can result in a negative calcium balance. With an intake of 140 grams of protein, there is a mean loss from the body of 60 mg of calcium per day, regardless of the amount of calcium ingested.

(c) Excess sodium (salt) consumption. This compromises the kidneys' ability to return calcium to the bloodstream. We need less than 500 mg of sodium per day, yet many Australians eat from 4 to 8 grams per day. For every excess gram (1000 mg) of sodium that you consume, you will lose about 40 - 50 mg of calcium in your urine.

(d) Caffeine consumption. Caffeine has similar effects to sodium. Researchers at the University of California, San Diego, found that drinking just two cups of coffee per day throughout adulthood significantly reduces bone density.

(e) Sucrose (sugar) consumption. Sugar increases the solubility of calcium in water (including blood) by thirty-five times. Having more calcium dissolved in the blood filtering through the kidneys means more calcium lost via the urine.

(f) Cigarette smoking. Nicotine strongly stimulates urinary calcium loss by interfering with hormones that direct the kidneys to reabsorb calcium.

(g) Phosphate and phosphoric acid. These substances, found in high amounts in:

soft drinks (along with sodium and caffeine)

red meat (especially processed meats)

cheese

instant soups and puddings

baked goods (phosphate is an additive in baking powder). Increase the release of parathyroid hormone, which mobilises calcium out of the skeleton. The average Australian's intake of phosphorus is double what it should be.

(h) Alcohol. Alcohol's diuretic action increases urinary loss of calcium. Alcohol also inhibits the action of osteoblasts, the cells that build new bone.

(i) Drugs such as diuretics, tetracycline antibiotics, anti-epileptic drugs and laxatives increase either urinary or faecal excretion of calcium. Corticosteroids increase the activity of osteoclasts which break down bone, and inhibit the bone-building activity of osteoblasts.

Thyroxine, heparin and cyclosporin are also known to contribute to osteoporosis.

PREVENTING AND REVERSING OSTEOPOROSIS

A person wishing to maximise their bone density and reduce their fracture risk needs to:

Avoid excess protein, as well as salt, refined sugar, caffeine, alcohol and other bone-robbing drugs.
Carry out regular weight-bearing exercise, for example, walking (use light 'walking weights' if desired, or just carry your groceries home), stair climbing and weight training (use only light weights or Dynabands if you have established osteoporosis: heavy weights can cause stress fractures in weakened bones). In building peak bone mass, exercise is most beneficial in the years before puberty, so encourage your children to be active in their leisure time.
Make fruit and vegetables the major part of your daily diet. Data from the Framingham Heart Study indicate that lifelong high daily dietary intakes of fruit and vegetables along with the minerals potassium and magnesium (which are abundant in fruit and vegetables) correlate with good bone density in elderly men and women.
Harvard University researchers studied over 72,000 women and found that those who ate lettuce every day - lettuce is rich in not only potassium and magnesium but also vitamin K which increases the absorption of certain bone-strengthening proteins into bone - had half the risk of hip fracture compared to those who ate lettuce once a week or less.

The alkaline minerals in fruit and vegetables buffer the acidity generated by normal digestion, preventing the loss of buffering minerals from bone.

Magnesium is also necessary for the proper absorption and utilisation of calcium, and adequate levels of magnesium (which most Australians do not obtain because of their dietary habits and/or use of the oral contraceptive pill) are probably mere important for bone health than calcium intake. Boron - another nutrient essential for bone formation - is also abundant in fruit.

4. Obtain regular exposure to sunlight - at least 10 minutes daily, avoiding the hours between 10 am and 3 pm. Don't wear sunglasses or sunscreen during this sunning period as both interfere with vitamin D synthesis.
5. Eat foods containing the essential fatty acids - 'healthy fats' -such as raw nuts and seeds. EFAs enhance calcium absorption and utilisation, reduce urinary excretion and increase the amount of calcium deposited in the bones.
6. Eat a wide variety of legumes and whole grains - the phyto-oestrogens and boron they contain may benefit your bones by increasing calcium absorption.
7. For women, breastfeed your children for as long as possible. Twelve months or more is ideal. Women who breastfeed their babies subsequently have significant improvements in bone mineralisation compared to women who don't. Women must be aware that nulliparity (the medical term for not having borne children) is a recognised risk factor for osteoporosis.
As with other diseases of civilisation, osteoporosis is best prevented by adhering to nature's blueprint for our species:

pursue physically active lives;

eat the foods to which we are best adapted;

avoid unnecessary natural and synthetic toxins.

REFERENCES

Available on request.

Robyn Chuter, ND, Grad Dip Couns, is a naturopath and counsellor practising in Cronulla, NSW, and is also Hopewood Health Centre's Stress Management Consultant. She can be contacted on 02 9544 0445.

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By Robin Chuter

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