Some of you may be aware that Vitamin D is vital for healthy bones but it is also vital for life. It promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralisation of bone. The vitamin is also required for bone growth and bone remodelling. But it also has multiple other metabolic functions including modulation of cell growth, neuromuscular and immune function and modulation of inflammation. Vitamin D modulates proteins that regulate cell proliferation and differentiation. These functions may play a role in protecting against certain forms of cancer.
However, to take in enough vitamin D from one’s diet can be tricky. The flesh of fatty fish such as salmon, tuna and mackerel and fish oils provide higher amounts of vitamin D. Smaller amounts are found in beef liver, cheese, egg yolks and mushrooms. Of course, many other foods maybe fortified with vitamin D such as bread, breakfast cereals, yoghurt, orange juice and margarine. It’s quite possible that many of the population don’t ingest enough vitamin D from their diet. But there is another way to absorb vitamin D. UVB radiation from direct sunlight on the skin stimulates subcutaneous 7-dehydrocholesterol to convert into vitamin D3 which in turn becomes vitamin D. But in the UK, the sun is only direct enough to stimulate this process during the spring, summer and autumn. Add to that that many of us now wear sunscreen with a sun protection factor of 8 or more every time we are in the sun, which screens out UVB striking the skin and that cloud cover also reduces the amount of UVB that arrives at ground level.
The strange case of the vampyric lawyer: One of my patients was rehabilitating from a badly fractured tibial plateaux (the top of the shin bone that forms the bottom of the knee joint). He had had surgery and had been diligent with his rehabilitation programme. He had improved his strength, stamina and range of movement and was far enough along the healing time frame for him to commence short runs on the treadmill. At first these were 30 seconds after 2 minutes of walking. Unfortunately, he experienced sharp pain in his recovering knee each time he did this. After the third time that he reported this pain, he was referred for an MR scan of the knee as the situation required clarity. The results of the MR scan showed a stress fracture of the tibia below the previous fracture. This was a strange finding considering he had been walking for some time and had run 1.5 minutes in total in three 30 second bursts. He had a blood test and was found to be vitamin D deficient. He was otherwise in good health and in his late 20s. He ate a healthy diet but hardly ever had fish. He had reduced his cheese and bread intake some years before to manage his weight, he didn’t eat eggs regularly, didn’t like mushrooms, had never eaten beef liver and didn’t eat breakfast cereals and had stopped drinking milk in his teens. He worked from 0700 to 1900 in a city nearly every weekday meaning even if he was outdoors, he was in shadow. Weekends would usually be half recovery and half away on day trips, which nearly always involved a journey inside some sort of transport. He also wore sunscreen when in the sun for longer periods during the spring, summer and autumn. It was clear that he hardly ever exposed his skin directly to the sun. He was amazed he could be deficient in such an important vitamin despite leading a relatively healthy lifestyle. This deficiency was the probable cause of his stress fracture.
To look after your bones and indeed the rest of your health, it is recommended that fatty fish form part of a healthy diet, eating several portions a week. However, it is also recommended that those of us resident in northern climes expose our unprotected skin to direct sunlight between 1000 and 1500 for 5 to 20 minutes (5 minutes for fair skin and 20 minutes for dark skin) several times a week during the spring, summer and autumn to make sure we all form enough vitamin D and store enough over the winter in our livers. Of course, don’t take risks with your skin health the rest of the time you are in the sun. It is recommended that sunscreen of a sun protection factor of at least 15 is used on a daily basis if exposed to direct sunlight.
For more information on vitamin D click here.
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