Vitamin D supplements — are they useless?
Osteoporosis is incredibly common. To quote the osteoporosis Australia website there is an estimated 1.2 million people living in Australia with the condition and a further 6.3 million people with low bone density. Although postmenopausal women are at the greatest risk for osteoporosis, well over 20% of males over the age of 50 suffer the condition as well. For postmenopausal women there is around a 2% per year bone loss for several years after the onset of menopause.
The Osteoporosis website also states that low calcium and vitamin D levels are strong risk factors for osteoporosis. They suggest that adults require around 1000 mg per day of calcium which increases to 1300 mg per day for women over 50 and Men over 70. The website also states that low vitamin D levels due to lack of sun exposure may imply you are not getting enough vitamin D which your body needs to absorb calcium. The website doesn’t mention that vitamin D is intricately involved in many aspects of calcium metabolism, not just absorption.
The other risk factors for osteoporosis including corticosteroid therapy for many inflammatory conditions, low hormone levels in both men and women, thyroid disease, malabsorption (the most common being coeliac disease) along with the number of chronic inflammatory conditions and medications.
The most important lifestyle risk factor is physical inactivity, closely followed by smoking, excessive alcohol intake and extremes of weight, either been too thin or obese.
In a recent edition of Lancet Diabetes and Endocrinology, a large meta-analysis was published of 81 randomised, controlled trials asking the question: does vitamin D prevent bone fractures and improve bone mineral density in adults? The study involved just over 53,500 people and all of the studies were for less than five years. The conclusion of the meta-analysis was that vitamin D had no effect on preventing bone fractures or improving bone mineral density in adults.
This study will prompt many people in conservative medicine to suggest that this is more evidence that vitamin supplements are of no value and trot out the age-old argument that all supplements do is give you expensive urine.
Interestingly, a few years back there was a large meta-analysis of calcium supplementation involving 100 studies asking the same question as the vitamin D meta-analysis. Again, this study showed no benefits for the use of oral calcium supplements for the prevention of bone fracture or the improvement in bone mineral density. But, most endocrinologists and conservative doctors are still recommending calcium supplementation despite the suggestion in some studies (although I must state this has been refuted in other studies) that oral calcium supplementation increases heart attack rate by around 30%.
So, is this the end of vitamin D supplementation? Should we purely return to 15 minutes of sunlight during the non-burning times on a daily basis?
I would like to make some very important points regarding this well done meta-analysis.
1) There is no doubt from a significant number of trials that there is a clear link between low vitamin D levels and a number of medical conditions including osteoporosis, cardiovascular disease, cancer, multiple sclerosis, type II diabetes, depression and asthma.
2) There is also no doubt that around 30% of the Australian population have vitamin D levels below the recommended range. Because Australia is the skin cancer capital of the world, we have embraced the slip slop slap message and therefore a significant minority of the population does not have adequate vitamin D levels
3) Many of the trials, not just in the osteoporosis area but also for the vast majority of common diseases, study people over the age of 50, although in the trial in question, people as young as 18 were included. Regardless, many of the people in these trials already have established disease or are at high risk for the condition once these trials begin.
4) I have stated on numerous occasions previously that vitamin supplementation in any form cannot be seen as the same as pharmaceutical therapy. I constantly make the analogy that pharmaceutical therapy is like a high-performance motorcar taking you from A to B very quickly but with the potential of crashing and killing yourself or possibly sustaining a major injury and thus the vital need for stringent road rules, Seat belts and high-tech safety equipment within the car. Vitamin supplementation is more like a bicycle which get you from A to B much slower but you also get some exercise along the way, the road rules are less rigid and all you really need to do is wear helmets and be careful of drivers. Pharmaceutical therapy has very strong, relatively immediate effects, whereas supplements are purely that, supplements to a healthy lifestyle, taking much longer to be effective with minimal side effects in most cases.
Therefore, we cannot apply the same rules of randomised controlled trials, which are vital for pharmaceutical drugs, to supplements because, in my view, it takes many years for the supplements to have a benefit. It is my view that if it is demonstrated that supplements do have an effect on the surrogate markers of risk & disease, this is enough justification for their use for all the reasons I have detailed above.
5) Now, here’s where the problem arises. Homo sapiens are a very disappointing lot who are not particularly good at compliance. If I prescribe any medication or supplement to a group of people, after 12 months only 50% are continuing to take therapy. It is my view that vitamin supplementation does have benefits when you look at the long-term observational trials (because no company can afford to perform randomised controlled trials that go for 10 to 20 years). There is a significant and consistent benefit from the use of certain supplements over this time. This is very true for multivitamins and fish oil which don’t appear to have any benefits until the trials are performed for 10 years and beyond as seen from recent randomised controlled trials of short-term supplements which showed no benefits whatsoever for the treatment or prevention of cardiovascular disease.
I’m not suggesting that there is absolute proof that the long-term ingestion of vitamin D does have a benefit for osteoporosis but what I am saying is that all the indirect evidence to date points to the fact that being deficient in vitamin D is associated with a number of diseases and that well monitored low-dose vitamin D is harmless and, in my view, should be used by a significant proportion of the population.
This large meta-analysis, although well performed with proper statistical analysis, does not answer any questions about whether vitamin D should or should not be used. I for one will continue to take 1000 I.U. of vitamin D on a daily basis and will continue to do so, not just for my bones, but for the health of the rest of my body.