SHINING A LIGHT ON VITAMIN D
As we have become more conscious of skin cancer prevention, we avoid the sun – either by covering up, not going out during the sunniest part of the day, or using high factor sunblock.
Iam often asked by patients whether or not they should take vitamin D supplements. This is a tricky one. The reality is that at present we probably don’t know the answer to this – and it becomes a conversation about the potential benefits versus the known risks, with a whole lot of ‘‘grey’’ areas thrown in the mix.
What we do know is: Vitamin D, known as cholecalciferol, is a fat-soluble vitamin that helps the body to absorb calcium, essential for bone growth and metabolism.
It also plays a part in a healthy immune system, neurological and muscular functioning. Vitamin D deficiency leads to soft, weakened bones – causing rickets in children, and osteomalacia and osteoporosis in adults.
Vitamin D’s role in preventing infections, heart disease, cancer, dementia and degenerative conditions such as multiple sclerosis is uncertain; there are associations with vitamin D deficiency and all of these conditions, but that doesn’t necessarily mean that vitamin D deficiency is the cause, or that treating it will help in any way. However, there is plenty of exciting research going on around the world, looking at vitamin D’s role, so watch this space.
We can only get vitamin D in three ways: from our diet, exposure to sunlight and supplementation with tablets. It is thought that around 95 per cent of our body’s requirements are gained through sunlight and the rest is made up of vitamin D obtained in our diets.
How much sunlight we need is a topic of debate. As we have become more conscious of skin cancer prevention, we avoid the sun – either by covering up, not going out during the sunniest part of the day, or using high factor sunblock. This means that our levels of sun exposure are significantly less than they used to be.
During summer, around 20-30 minutes of sun three times a week, with arms and face exposed, is thought to be enough to sustain our levels – but this is likely to be inadequate over winter when sunny days are a much rarer occurrence.
It is hard to know how to balance the risk of getting too much sun, with the risk of vitamin D deficiency if you don’t get enough – trying to get sun exposure during a less ‘‘risky’’ part of the day is one way over the summer months (so going outside for half an hour in short sleeves early in the morning or later in the afternoon), but this isn’t necessary over winter when the sun’s potency is so much lower.
If you are concerned you don’t get enough vitamin D through sun exposure, it is possible to get a small amount in your diet as well, but not enough to meet all your daily requirements.
The foods to concentrate on include oily fish, eggs, milk, cod liver oil, cheese and mushrooms. Certain foods are also fortified with vitamin D, so check the labels of products such a breakfast cereals and breads to see if you could add any extra to your diet this way.
Aside from dietary deficiency and low exposure to sunlight, we know that certain people are at particular risk of deficiency – if you fall into one of these groups it is a good idea to discuss the use of supplements with your doctor:
Breast-fed babies, especially those over 6 months of age who are still exclusively breast fed (breast milk doesn’t contain a lot of vitamin D).
People over 65 – as we age, our skin isn’t as effective at using sunlight to make vitamin D, and our kidneys become less able to convert vitamin D to its active form. Very elderly people are especially at risk, as they are often housebound or immobile, limiting their exposure to the sun.
Anyone with darker skin – the increased melanin in dark skin inhibits the absorption of sunlight and hence predisposes to vitamin D deficiency. In New Zealand Pacific people are two to three times more likely to have vitamin D deficiency than nonPacific people.
Obese people.
Lower socioeconomic status – higher deprivation is associated with higher levels of deficiency.
People with bowel disease who don’t absorb fat properly, this includes people with coeliac disease and Crohn’s.
People with osteoporosis.
Gastric bypass surgery patients.
People with hyperparathyroidism, TB, sarcoidosis, or lymphoma.
Certain medications can also lead to reduced vitamin D levels, including anti-seizure drugs, glucocorticoids, antifungals and HIV medicine.
Symptoms of vitamin D deficiency can include muscle aches and pains, joint pains and fatigue. However it often presents in a vague and nonspecific manner, and there may be no indication at all, until osteoporosis is detected either through a fracture in a weakened bone or at a bone density scan.
It is possible to do a blood test for vitamin D
deficiency but it is an expensive test and not recommended routinely unless you have a particular risk. If you fall into one of the high risk groups above or have any symptoms, I would talk to your doctor about testing – if you do find out you have proven deficiency, you definitely should take supplements.
For the rest of us, the jury is really out as to whether or not we should routinely supplement ourselves over winter.
It’s hard to know what to advise as it’s a very personal choice. There are risks of having too much vitamin D in your system, but if you are careful about the dosing (many vitamin D supplements are given as a once monthly tablet and you shouldn’t exceed this), those risks are minimal and are likely outweighed by the benefits to our bones.
As for the benefits to the rest of our body, ongoing research will hopefully provide a body of scientific evidence in the coming years to inform this debate, making the question about supplementation a lot clearer.