OVERVIEW
· Throughout our evolution we have been exposed to sunlight, which triggers the production of vitamin D in our bodies.
· Concerns about skin cancer mean that many of us avoid exposure to the sun, with the result that our vitamin D levels have plummeted.
· Vitamin D is essential for preventing the childhood bone disease rickets, but our vitamin D levels have become so low that we are now seeing a re-emergence of this virtually forgotten condition.
· This is just the tip of the iceberg: vitamin D is vital at every stage of life and we need it at far higher levels than are currently endorsed.
· We expose a developing osteoporosis time bomb, and a government with a lot to answer for when it comes to protecting our health.
At the turn of the twentieth century, the crippling disease rickets was prevalent in the industrialized world. With the subsequent discovery that a simple nutrient, vitamin D, could eradicate this scourge on children’s health, you’d be forgiven for thinking that rickets was banished to the history books, and that the whole vitamin D story had reached a satisfactory conclusion. You’d be wrong on both counts. Research into vitamin D is red hot right now and the last decade has revealed some breathtaking findings. Some scientists researching vitamin D estimate that there could be as many as one billion people worldwide not getting enough of it1, making vitamin D deficiency one of the most pressing medical conditions of our times.
Although it’s the subject of some intense debate, when it comes to the health of our skeletons, only the most stubborn would disagree that we need a vitamin D level in the body of at least 20ng/ml for strong bones. Using this minimal figure as a guide means that a third of the US population is vitamin D deficient, increasing to almost three quarters of non-Hispanic blacks2. And, as we’ll see in chapter 7, even these figures give a rather rose-tinted view of the true extent of the problem.
Cross the Atlantic and things are grimmer still. In the UK, during the winter and spring, over half the population have vitamin D levels below those needed for healthy bones3. Even in the summer and autumn, when vitamin D levels from sunshine reach their peak, significant numbers still languish below this threshold3. As improbable as it may seem in an era of high-tech medicine, there’s even a re-emergence of rickets in the UK, particularly in ethnic minorities. So much for progress! Yet, as disturbing as the prospect of rickets is, more worrying still is the fact that low levels of vitamin D in the general population mean that our skeletal health is under serious threat, and the risk of osteoporosis and bone fractures looms large.
Vitamin D levels among the UK’s South Asian population are of particular concern. Figures from Surrey, in the south-east, where vitamin D levels are typically higher than further north, show that 76% of South Asian women have levels less than 10ng/ml in spring, and even in summer the average level of vitamin D barely reaches 10ng/ml4.
All this may sound alarming and depressing in equal measure, but the good news is that the problem is easily resolved by ensuring we get enough vitamin D. Simple. Well, we say simple, except for the fact that governments and health agencies are being monumentally slow when it comes to sorting out this mess. We’re not prepared to wait, however, and will tell you how to safely boost your vitamin D levels into the range needed for healthy bones.
VITAMIN D
All this fuss about vitamin D becomes a bit clearer when we look at its indispensable role in promoting a healthy skeleton. Bones need much more than just calcium. A bit like the great comedy double act Laurel and Hardy, bone health relies on the successful interchange between the duo of vitamin D and calcium. One of vitamin D’s most vital roles is to increase the amount of calcium in the bloodstream. It does this by promoting the absorption of calcium from the gut, and also by acting on the kidneys to prevent it being flushed away in the urine. Getting more calcium into the bloodstream in this way encourages the mineralization of the skeleton. Vitamin D also has direct effects on the skeleton, helping to form the matrix of bone and aiding bone tissue to develop5.
If vitamin D levels are low, however, our blood calcium levels are reduced and, in response, the body releases parathyroid hormone (PTH). This also works to increase our blood levels of calcium. Unlike vitamin D, however, it targets the body’s greatest calcium stores, our bones. PTH triggers the process of demineralization, releasing calcium from the bones back into the bloodstream. To preserve the mineral content of bone, it is desirable to minimize bone breakdown by reducing PTH production by having sufficient vitamin D levels.
Vitamin D is converted by the kidneys into 1,25-dihydroxyvitamin D, or 1,25(OH)2D for short. This is the most active form of the vitamin, and at this stage it is more correctly classed as a hormone rather than a nutrient/vitamin.
Current UK recommendations are for vitamin D levels greater than 10ng/ml, to prevent the onset of rickets in children, and the adult equivalent, osteomalacia. But there is now a stack of evidence that conclusively shows that when it comes to vitamin D and our bones we shouldn’t be drawing the line at this traditionally advocated cut-off (10ng/ml). In fact, it’s way off the mark. It should be two, or even three times higher (20–30ng/ml). Studies show that within this range calcium absorption6 and parathyroid hormone suppression7,8 are maximized. If the fact that 15% of the UK population have levels below the absolute ‘bare minimum’ of 10ng/ml isn’t shocking enough, when we apply the higher figure of 30ng/ml, we’re looking at almost 90% of the population falling short during the winter months3.
It is known that for every 10 degrees change in latitude away from the equator (where the sun is strongest) the probability of having a hip fracture increases9.
In 2002, it was estimated that 44 million people over the age of 50 in the USA were at risk of fracture due to osteoporosis, or low bone mass. The economic burden of osteoporotic fractures in the USA alone was estimated at nearly $17 billion in 2005.
Stuck in the dark ages
The fact is that much of the current health advice is out of step with advances in the field of vitamin D research. Despite soaring rates of vitamin D insufficiency, the UK is the only country in Europe with no recommended vitamin D intake for ‘healthy’ adults. Even in vulnerable groups the recommendations remain a deplorable 400IU per day (an amount intended only to ensure levels of 10ng/ml are reached). Incredibly, the UK’s National Osteoporosis Society, which is dedicated to ‘improving the diagnosis, prevention and treatment of osteoporosis’, released a unified statement with the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum and the Primary Care Dermatology Society on 16 December 2010, stating that ‘raising the definition of “deficiency” or “sufficiency” to higher levels (>10ng/ml) is inappropriate’.
We’re just perplexed by this sort of advice. Just two weeks prior to this announcement, the highly respected Institute of Medicine in the USA published their recommendations after an extremely lengthy and thorough analysis, reviewing more than 1,000 publications. They affirmed that vitamin D has a pivotal role in skeletal health and that levels of 10ng/ml were simply too low. They determined that, for maximum benefits for bone health, the science backed a level of at least 20ng/ml (so, twice as much), thus making the UK recommendations appear even more out of touch. Earlier in 2010, Osteoporosis Canada increased their vitamin D recommendations to a minimum level of 30ng/ ml. Furthermore, they recommended that all patients presenting with osteoporosis be investigated for the likely event of vitamin D deficiency.
While the UK still supports the antiquated view that a vitamin D level of 10ng/ml is sufficient, we urge you to ignore this recommendation. Instead, look further afield, to the USA and Canada, where improving the health of the population in this area appears to be a higher priority.
Storing up future problems
The whole situation is a mess, and you need only look at the state of bone health in the modern world to see why. One out of every two women and one in four men over 50 will have an osteoporosis-related fracture in their lifetime. In the USA alone, ten million people have osteoporosis and another 34 million have low bone mass, putting them at greater risk of osteoporosis in the future10. Put all of this in the context of an ageing population, and we have a recipe for disaster. An old proverb tell us that ‘prevention is better than cure’, and to us, all these depressing numbers lead us to one inescapable conclusion: improving our vitamin D levels is not a luxury, but a necessity.
While we traditionally regard osteoporosis and suffering from fractures as diseases of advancing years, it’s now apparent that promoting the health of our bones should be high on the agenda throughout our lives, in fact, right from day one. By developing strong bones in our formative years – what’s known as achieving an optimal ‘peak bone mass’, usually attained by age 30 – the risk of osteoporosis in later life is greatly diminished. And getting enough vitamin D is critical every step of the way.
In fact, the importance of getting enough vitamin D for healthy bones begins before birth. It has been proposed that future risk of fracture might be ‘programmed’ during intrauterine life, with a mother’s lack of vitamin D during pregnancy compromising how the bones of her offspring build up minerals early in life11. It’s worrying enough that vitamin D deficiency is rife among mums-to-be, but if we add in the fact that a foetus is only exposed to 50–60% of its mother’s circulating vitamin D levels12, it’s not difficult to see that we’ve got a big problem of vitamin D deficiency starting in-utero and in newborns.
But does any of this really matter in the long run? It appears the answer is a resounding ‘yes’. In otherwise healthy pregnant women in the UK, having low levels of vitamin D during late pregnancy has been linked to reduced bone mineral content in their children almost a decade later13. Could addressing the vitamin D status of pregnant women be an effective strategy for stemming the rising tide of osteoporotic fractures in future generations? To us, it’s obvious, but as we’ll see in later chapters, it’s still deemed perfectly appropriate to recommend an inadequate 400IU of vitamin D per day to pregnant and lactating women.
Let’s jump on a stage. Vitamin D deficiency is common among children and adolescents, particularly during the winter months. In otherwise healthy US teenagers, the prevalence of vitamin D deficiency was found to be 42%14. In France, male adolescents had an average vitamin D level of a mere 8ng/ml, when measured at the end of winter15, way short of what’s needed for healthy bones. What impact could this have? Well, in post-pubertal girls aged up to 15 years, those with an average vitamin D level of 18ng/ml (which is still below ideal) had a 6.4% higher bone mineral content at the lumbar spine than those with levels of 8ng/ml16,17. In young Danish men aged 20–29 (i.e. just hitting peak bone mass), those with vitamin D levels lower than 20ng/ml had a 2–3% lower bone mineral density compared to those with levels of 30ng/ml and above18.
The consequences for the future of our bone health are worrying indeed. The reported changes in bone mass or density may not seem very large, but it only takes small changes to have a detrimental impact. Taking the last study as an example, if this seemingly small 2–3% reduction in bone mineral density was maintained into later life, this would translate into a predicted increased risk of vertebral fracture of 35%, and hip fracture of 80%18. Stack all this evidence up and we reach one conclusion: by not ensuring that pregnant women, infants, children, adolescents and young adults receive enough vitamin D, we’re creating an osteoporosis time bomb.
Fractures and falls
It’s high time that seniors got a look in too, as we ask the question: can vitamin D actually help to reduce the risk of getting fractures in later life? A large RCT in the UK found that raising vitamin D levels from 21ng/ ml to 29ng/ml throughout a five-year period produced a 33% reduction in all major osteoporotic fractures combined19. A key finding from studies is how important it is to get your vitamin D levels above that all-important threshold of 20ng/ml, and the current UK recommendations for a vitamin D intake of 400IU per day just isn’t enough. In a meta-analysis of 12 RCTs, supplementing 400IU or less had no effect on fracture incidence20. But in individuals who supplemented higher than this dose (averaging 482–770IU daily), non-vertebral fractures were reduced by 20% and hip fractures by 18%.
A 70-year-old has only about 25% of the capacity for making vitamin D compared to a 20-year-old. Couple this with a sedentary lifestyle and we can see that the elderly are a group at massive risk of severe vitamin D deficiency.
In the institutionalized elderly, supplementation with calcium (1.2g/day) and vitamin D (800IU/day) for 18 months reduced hip fractures by 43%, and the total number of non-vertebral fractures by 32% compared with those receiving a placebo21. Whereas measures of bone density decreased in the placebo group, supplementation actually caused an increase. While getting enough vitamin D is really important for preventing fractures in the elderly, it is worth remembering that vitamin D and calcium work in concert with one another, and optimal benefit is likely to be achieved from a combination of the two nutrients22,23.
The death rate within one year of suffering a hip fracture is between 20% and 35%24.
There’s a whole other dimension to the vitamin D and bone fracture story. As well as having a direct effect on the health of bones, studies have shown that vitamin D also improves muscle strength and function25, which can significantly reduce the risk of falls. And once again, the key is to get those vitamin D levels above 20ng/ml. Compared with having higher levels of vitamin D (above 30ng/ml), having low levels (below 20ng/ml) is linked to worse physical performance and a greater deterioration in physical performance over a three-year period in both older men and women26. A meta-analysis of RCTs found that having a vitamin D level of 24ng/ml and above reduced the risk of falls by 23%27. Unsurprisingly, it was noted that vitamin D supplementation at traditionally recommended levels (200–600IU/day) had no impact when it came to reducing falls.
More than 90% of the annual 264,000 hip fractures in the USA occur after a fall, which means if falls could be prevented, it would greatly reduce the incidence of fracture28.
THE PARTING SHOT
When all’s said and done, there are two things that determine the risk of getting osteoporosis. First, the extent to which optimal peak bone mass can be achieved during the first two or three decades of life. Second, the rate at which bone is lost as we age. Getting sufficient vitamin D is vital for both.
This means we shouldn’t just focus on older people in an attempt to reduce fractures (although that is clearly important, too), but need to start right from day one. Low levels of vitamin D are rife in people from all walks of life, at every age and stage. Traditional recommendations of 10ng/ml belong in the twentieth century. They should be at least twice, and maybe even three times higher.
SUMMARY AND RECOMMENDATIONS
· An adequate level of vitamin D is required for healthy bones at every stage of life.
· Traditionally, a vitamin D level of 10ng/ml has been seen as adequate, but current evidence shows this is not the case.
· For optimal bone health, you should be aiming for a minimum of 20ng/ml, and possibly up to 30ng/ml.
· Boosting your vitamin D to these optimal levels will help reduce the risk of suffering a fracture, and can significantly reduce the risk of falls.
· For maximum fracture prevention in the elderly, combining vitamin D with calcium is likely to be even more effective. Elderly people should aim to get up to 1,200mg of calcium per day through diet and/or supplements.
· In Chapter 7 you’ll find out exactly how to boost your vitamin D levels into the most desirable range.