Calcium and Osteoporosis
In terms of health horrors, osteoporosis, it is said, is the new breast cancer. It is also referred to as a ‘silent disease’ because most people don’t know they have it until they fracture a bone.
Having recently spent some time on an orthopaedic ward as a result of an accident (see The Motorbike and Me) I started to appreciate the enormous scale of the problem posed by osteoporosis and an ageing population.
Osteoporosis literally means 'porous bones' and involves changes in the amount and variety of proteins, a reduced bone mineral density (BMD) and an altered microarchitecture of the bone. This leads to a weakening that can cause either spontaneous fractures or fractures with little provocation - most often of the vertebrae, hip, wrist or ankle.
Many of the mostly elderly ladies on the ward were there with their second or third osteoporotic fracture. Many required extensive nursing care over prolonged periods of time and many were widows with little support at home.
So we have a huge and growing problem on our hands, but are we addressing it in any meaningful way?
The commonly accepted explanation for osteoporosis is that it is primarily due to a lack of calcium combined with a lack of exercise. The current 'conventional' treatment relies upon the twin-pronged approach of using pharmaceuticals and calcium supplements.
But is this an overly simplistic explanation for this debilitating disease?
Osteporosis: The statistics
According to the UK National Osteoporosis Society, half of all women and one in five men over the age of 50 will break a bone. In the UK, 2 million women are affected by osteoporosis and a further million are considered to be at risk, more than a quarter of whom are over 80 years of age. A 50 year old Caucasian woman is estimated to have a one in six chance of future fracture of her hip and in the UK, hip fractures alone cost the NHS an estimated £1.7 bn a year.
In the US, osteoporosis affects 1 in 3 women and 1 in 12 men over the age of 50. Nearly half of all women in the US aged 50 or over have had at least one vertebral fracture and two-thirds of these go unrecognised. One in five women will have had a wrist fracture by the age of 70 contributing to an annual total of 250,000 wrist fractures. Add to this the 250,000 hip fractures that occur annually in the US and you will start to appreciate the scale of the problem.
The chances of having another fracture increase with each fracture and with every passing decade over the age of 50 years of age.
Symptoms of osteoporosis
A spontaneous fracture of the spine may cause sudden back pain and multiple vertebral fractures can lead to loss of height, and the stooped deformity known as a ‘dowager’s hump’ or kyphosis.
Fractures of the hip acutely impair mobility and may require surgery. One in seven people will die within 6 months of a hip fracture often as a result of enforced inactivity leading to complications such as deep venous thrombosis, pulmonary embolism and/or pneumonia. Only one in three people return to their previous level of function after breaking a hip and some sufferers may end up confined to a wheelchair.
Risk factors for osteoporosis
There are many factors that contribute to the risk of breaking a bone and some of these are related to the environment and to age. Environmental factors can include rugs, slippers, poor lighting and so on. Factors associated with ageing include poor balance, poor eyesight, and slow or difficult movement.
Other factors associated with an increased risk of osteoporosis include:
Being a post-menopausal woman and/or having an early menopause
A history of irregular menstrual cycles in women
Having Caucasian or Asian ancestry or a family history of osteoporosis
Regular consumption of 3 or more units of alcohol a day
Vitamin D deficiency which may occur in the elderly as a result of being confined to the house or not exposing skin when in the sun
Smoking which inhibits bone formation and may also contribute indirectly through reducing oestrogen levels, inducing an earlier menopause, malnutrition or low body weight
Excessive consumption of salt (sodium) which increases excretion of calcium in the urine
Deficiencies of nutrients such as vitamin K (found mainly in lettuce) and vitamin B12
An imbalance of omega 6 to omega 3 oils
Excessive exercise such as marathon running
Both high protein and low protein diets. High protein diets create an acidic environment which causes calcium to be leached from the bones in order to neutralise the blood which is ultimately excreted in the urine. Low protein diets may be associated with malnutrition and low vitamin and/or mineral intake.
Being underweight is thought to contribute both through malnutrition and because the body weight is not sufficient to induce bone formation. Osteoporosis is rare in overweight people.
Digestive disorders which affect absorption such as coeliac disease, Crohn's disease, lactose intolerance, gastric, intestinal or bowel resections or bypass surgery.
Malnutrition through conditions such as anorexia and/or bulimia, particularly if severe enough to cause the periods to stop in a woman
Inactivity especially when young reduces the peak bone density which occurs in the thirties thus creating problems in later life as bone mineral density levels fall
Exposure to heavy metals such as cadmium, lead and/or mercury impair all cell functions, deplete calcium stores and substitute for structural calcium within the bone
Consuming soft drinks containing phosphoric acid leaches calcium from the bones in order to neutralise the acid
Consumption of dairy products - in spite of containing calcium - are also high in phosphates and protein, both of which may draw calcium from the bones
Endocrine disorders such as under-function of the ovaries or testes, both underactive and overactive thyroid and adrenal gland disorders and hyperparathyroidism
Rheumatologic disorders such as rheumatoid arthritis and lupus are associated with osteoporosis, either as a direct result of the illness or as a result of steroid therapy
Diseases such as Parkinson's disease and chronic obstructive pulmonary disease (COPD) also make osteoporosis more likely which may imply a common causation
Consuming more than four cups of coffee a day
A history of recreational drug use
Pharmaceuticals associated with an increased risk of osteoporosis include:
Over-medicating with thyroxine
Anticoagulants such as heparin and warfarin
Proton pump inhibitors to reduce stomach acid are thought to interfere with calcium absorption
Antacids containing aluminium may bind phosphates
Chronic lithium therapy
The currently accepted measure of osteoporotic fracture risk is to measure bone mineral density. Conventional x-rays, CAT and MRI scans are not sensitive to the early stages of bone loss and so have limited value in detecting osteoporosis. The first line screening may involve an ultrasound scan of the heel bone. The current industry standard is the Dual Energy X-ray Absorptiometry or the DEXA scan and this may or may not be accompanied by blood tests to identify any underlying cause(s).
Testing blood levels for calcium is not particularly instructive because the body maintains circulating levels within tight limits. Other tests include an osteoporosis bone turnover test which is a simple urine test conducted at home, and some also consider hair mineral analysis a good indicator of calcium turnover.
But is bone mineral density (BMD) as established by the DEXA scan a valid measure of osteoporosis risk? The following data suggests otherwise:
Countries with high mean bone mineral density scores demonstrate fracture rates in the elderly significantly higher than in countries with low mean BMD scores. These differences were established not to be genetic.
People suffering with hyperparathyroidism who are developing osteoporosis often show high BMD levels.
In fluorosis where people have been exposed to excessive levels of sodium fluoride either through fluoridation of the water supply, toothpaste or topical fluoride treatments, bone mineral density is typically increased - and so is fracture risk.
Studies of supplements that have successfully increased bone mineral density such as vitamin D have often failed to show a reduced fracture risk.
So although the minerals give the bone strength it may be the matrix of extracellular proteins which give bone its elasticity and fracture resistance. At best, bone mineral density may be only a snap-shot of bone strength and may not represent a long term measure of fracture risk.
How bones are formed
Bones consist of surface bone or cortical bone which is arranged in tree-like ring structures to provide strength. The inner sponge-like bone within the ends of long bones and vertebrae is referred to as trabecular bone.
The underlying cause of osteoporosis is an imbalance between the laying down of bone by cells known as osteoblasts and the resorption of bone by osteoclasts. This is a very dynamic process with up to 10% of the bone being remodelled at any one time according to the stresses placed on the bone. The osteoblasts and osteoclasts inhabit the surfaces of bones, and for this reason the remodelling of trabecular bone is more active and the sites that most commonly fracture have a high proportion of trabecular bone relative to cortical bone. The activity of the osteoclasts is ultimately regulated by substances produced by the osteoblasts.
In health, osteoblasts respond to an influx of calcium by composing a matrix upon which calcium can precipitate. In the process, up to 70% of the osteoblasts involved die. The more calcium, the greater the level of osteoblast activity, and the greater the programmed cell death rate of the osteoblasts (apoptosis rate).
As this process accelerates, the ability of the osteoblasts to mature and replicate becomes exhausted. Eventually the osteoblasts cannot be produced in sufficient quantities and bone density is not maintained. This process may become poisoned or exhausted with age accounting for the age-related nature of osteoporosis.
Factors which affect the rate of bone deposition and resorption include a lack of oestrogen which decreases the deposition of new bone and levels of parathyroid hormone secreted by the parathyroid glands. This hormone is produced in response to low blood calcium levels and increases bone resorption in order to boost blood calcium levels. This is countered by the hormone, calcitonin, produced by the thyroid gland which increases bone deposition when blood calcium levels rise.
Pharmaceutical treatment of osteoporosis
The main class of drugs used in osteoporosis work by preventing resorption of bone and these include the biphosphonate drugs such as Fosamax, Actonel, Boniva, Didronel and Reclast. These drugs work by effectively killing the osteoclasts over time and it is thought that they may actually contribute to the later development of osteoporosis. Somewhat alarmingly, 94 percent of patients with a broken femur had been taking bisphosphonate drugs - the majority for more than five years. These drugs are relatively poorly absorbed, and therefore need to be taken on an empty stomach, with no food or drink to follow for the next 30 minutes.
Biphosphonate drugs sales are currently estimated to be worth over £8.3 ($12) billion worldwide and over half a million prescriptions for Fosamax alone are dispensed in England annually according to NHS figures. Side-effects include oesphageal inflammation and cancer, osteonecrosis of the jaw, irregular heartbeat, palpitations, fatigue and fainting and more rarely congestive heart failure, blood clots and stroke.
Other drugs such as Raloxifene are Selective Oestrogen Receptor Modulators which stimulate osteoblast activity. Hormone replacement therapy (HRT) has also been used to boost protective blood oestrogen levels - although this brings other significant health risks.
The pharmaceutical companies have been criticised in a study published in the British Medical Journal (BMJ) for greatly exaggerating the benefits of these drugs. One study of Raloxifene, for example, quoted a 75 per cent reduction in 'relative risk' but that translated to less than a 1 per cent reduction in absolute risk.
Calcium supplementation and osteoporosis
The results of studies into supplementing calcium in order to prevent or treat osteoporosis are - at best - mixed. A study published in the British Medical Journal and conducted jointly between researchers in the UK and New Zealand, conducted a meta-analysis of five trials involving 8,000 subjects into the effectiveness of calcium supplementation in osteoporosis with and without vitamin D. They found that calcium supplements of more than 500 mg a day were associated with a 31% increased risk of heart attack, a 20% increase in the risk of stroke and a 9% increase in mortality.
Another study published in the Journal of Clinical Endocrinology & Metabolism conducted by Richard Prince at the University of Western Australia, showed that whilst calcium supplementation alone may produce initially encouraging results in osteoporosis sufferers, the reduction in bone turnover was no better than a placebo after 5 years.
Prophylactic calcium supplementation in women at low risk of osteoporosis has certainly not been established to provide any benefit and may do more harm than good. In fact, calcium supplementation may exhaust the processes of bone maintenance by promoting the creation of immature osteoblasts, accelerated cell death and although dense, the bone produced may be weak and immature.
The two main forms of calcium supplements used are calcium carbonate and salts such as calcium citrate.
Calcium carbonate is the cheapest form of calcium as it is literally mined from the ground. It is insoluble and this form is not found in either plant or animal sources and is not readily bio-available for use by the body as it is difficult to digest and absorb. If you have low levels of stomach acid - and one study found that up to 40 percent of post-menopausal women were severely deficient in stomach acid - then you will absorb as little as 4 percent of the calcium in such products.
Calcium carbonate also needs to be taken with food to maximise absorption. A study, led by Ian Reid at the University of Auckland, New Zealand, found an increased risk of heart attacks and other cardiovascular problems in healthy post-menopausal women taking calcium supplements and this confirms findings from other similar studies.
Calcium citrate, lactate and gluconate are all water soluble forms and studies have shown that whilst more expensive, they are absorbed four times more efficiently than calcium carbonate. These products also have the advantage of not needing to be taken with food and not being dependent upon stomach acid levels for absorption. Calcium in the form the body uses it in is calcium hydroxyapatite and some manufacturers supply calcium supplements in this bioavailable form.
Recommendations for calcium intake vary depending upon country and age, but in the US recommendations for women at risk over the age of 50 are 1,200 mg per day.
Is osteoporosis a calcium deficiency?
Some of the data that suggests that calcium deficiency is not the primary cause of osteoporosis is itemised below.
Osteoporosis is most common in countries where dairy products are consumed in the greatest quantities - the United States, Finland, Sweden and the United Kingdom
The average bone mineral density levels of healthy women in Poland are lower than those found French, Italian and Spanish women and yet the incidence of hip fractures is also lower
The average bone mineral density levels found in Sweden are higher than many other countries and so are their rates of osteoporotic fractures
Some populations consume only 200 mg of calcium on average a day and yet have stronger bones than people in the West who are advised to consume 1,200g of calcium a day.
70 year old women in developing countries have stronger bones than 40 year-old women in the U.S. deriving most of their calcium from plants - not dairy - products
As reported in The Lancet, when the remains of an 18th century woman found beneath a church were analysed, the bones were found to be denser than the bones of any modern women
Japanese and Chinese women who consume little dairy have lower bone mineral density than European and American women and yet a greatly reduced incidence of hip fracture (not due to genetic differences)
Within 12 years of immigrated to Denmark, pre-menopausal Chinese women demonstrate the same levels of bone density as the indigenous Danish population
African Bantu women take in only 350 mg of calcium per day, have an average of nine children who they breast feed for two years and yet they never have calcium deficiency and rarely break a bone
The Inuit have the highest dietary calcium intake of any people in the world at more than 2,000 mg a day from fish bones and they also have one of the highest rates of osteoporosis in the world
So, if osteoporosis is not calcium deficiency, what is it?
Four theories may contribute wholly or in part of the rise of this disease of modern life.
The first of these is exposure to heavy metals, particularly lead which replaces the structural calcium in the bones with non-structural and toxic lead. For many people their biggest source of exposure may either have come from leaded water pipes causing contamination of the water supply in an older house or from maternal exposure passed on in the womb or the breast milk.
Another chief suspect is the typical western diet containing proteins, refined grains and sugars, which is acid forming. People eating this diet have four times as many hip fractures as those in countries whose diets are the least acid-producing. In order to neutralise the acid conditions the body draws calcium from the bones and this is then excreted in the urine.
The third theory, expounded by Robert Thompson M.D., the author of The Calcium Lie is that bone mineral density is not primarily a calcium issue, but an issue of a dozen or more minerals that may now be deficient in our diets as a result of modern farming practices. He suggests that by supplementing calcium, relative deficiencies and imbalances of other minerals are created that may account for the adverse health effects observed when supplementing calcium.
Lastly, a deficiency of vitamin D from a lack of exposure to ultraviolet light may be partly or wholly responsible for the way calcium is metabolised and bone is formed.
Recommendations for preventing osteoporosis
So what are the take-away messages?
Exercise and particularly exercise when relatively young is important because it determines bone mineral density for a lifetime.
General Eat a healthy, whole food diet including plenty of fresh fruit and vegetables to create alkaline conditions.
Vitamin D is essential to aiding the absorption of calcium from foods, to regulating blood levels of calcium and phosphorus and also to proper parathyroid hormone regulation. It can be obtained from supplements, from the diet and from the actions of ultraviolet light on the skin. If supplementing, check the label for vitamin D3, which is more easily absorbed than vitamin D2. Foods rich in vitamin D include milk, egg yolks, oily fish, broccoli, molasses, wheat germ and kelp.
Calcium Milk and dairy products have always been considered to be good sources of calcium, but studies of dairy foods and bone health have failed to support this popular belief. In fact, milk may actually contribute to osteoporosis because in spite of containing high levels of calcium, cow's milk also contains high amounts of protein and phosphorous and is therefore acid forming. Other dietary sources include bread (which has calcium added); sardines and pilchards eaten with their bones; leafy green vegetables; dried fruit; broccoli and cabbage and tofu and nuts.
Vitamin C aids collagen production and this gives the bones elasticity and holds the bone matrix together. The richest food sources of vitamin C include citrus fruits, kiwi fruit, sprouted seeds, black currants, tomatoes and peppers.
Vitamin B complex These supplements will provide folic acid which helps to detoxify homocysteine, a toxic breakdown product of the amino acid, methionine, which has been associated with an increase in bone loss and vitamin B6 which has been shown to be deficient in people with osteoporosis.
Magnesium appears to be very important to bone metabolism since half our body stores are found in our bones. Magnesium helps in metabolising calcium and vitamin C and also in converting vitamin D to the active form required to ensure that calcium is efficiently absorbed by your body. The richest food sources of magnesium include nuts and seeds; wheat germ; leafy green vegetables; garlic; brewer's yeast; apricots; molasses and buckwheat.
Essential fatty acids Eat plenty of essential fatty acids from cold pressed oils, nuts and seeds, but avoid almonds and cashews.
Trace minerals Boron, a trace mineral, is also needed for the prevention of osteoporosis, as it plays a crucial part in the conversion of vitamin D into its active form. Trace mineral supplements or including salts in cooking and at the table such as Himalayan salt which have a complex mineral profile may help to prevent and treat osteoporosis.
For more about The Calcium Lie by Robert Thompson M.D. click for Amazon UK or US, or click for more books on related topics.