Vitamin D


Vitamin D is a fat soluble vitamin which is not found naturally in many foods. However we can manufacture vitamin D in our skin when it is exposed to ultraviolet light, hence it is often known as the Sunshine Vitamin. For many people living in more Northern regions, this synthesis in the body is inadequate and unreliable, especially in autumn and winter. For this reason, many processed foods have traditionally been artificially supplemented with vitamin D. Oily fish are the best natural source of vitamin D. (Oil extracted from the livers of cod was the original supplement). Vitamin D is also found in small amounts in red meats, liver and egg yolks1.


Vitamin D is known traditionally for its ability to help with the absorption and metabolism of calcium. Without enough vitamin D, children can develop rickets (malformed bones) and adults get osteomalacia (weak and painful bones). It is now recognised that vitamin D is associated with many other functions in the body. These include modulation of cell growth, neuromuscular and immune functions, as well as reduction of inflammation1,2. There has been a lot of research into the potential benefits of taking Vitamin D to help with the prevention and treatment of various conditions including multiple sclerosis, cardio-vascular disease and cancer. So far the evidence has not been conclusive. Given that vitamin D has such a wide range of effects in the body, it is likely that some degree of supplementation is sensible for people who do not have enough sun exposure throughout the year. In the UK this includes most people during autumn and winter. It applies through the entire year for people who get minimal sunlight on their skin. Very dark skinned people, such as those with an African, Afro-Caribbean or South Asian origin, might be best advised to take supplements through the entire year in the UK.


For most people 10 micrograms per day, which equals 400 IU (international Units), would be appropriate.  This is in line with advice from The British Nutrition Foundation, following information from The Scientific Advisory Committee on Nutrition3. Those who spend enough time in the sun during spring and summer might not need vitamin D supplements during this time. However the above recommendations would not be excessive.

Many people choose to take higher levels of supplementation than the above guidelines. The scientific evidence supporting this is inconclusive. From the history of vitamin D supplementation, it is likely that these low levels of supplementation are fully adequate to help with the metabolism of calcium and phosphate. This helps keep bones, teeth and muscles up to strength. The cause for uncertainty comes from the fact that vitamin D is now known to have so many other functions in the body. A slightly higher intake might help some people avoid a whole range of other health issues. Much research is ongoing on this at the moment and the jury is out. Vitbox does supply a higher dose supplement at 25 micrograms (1,000 IU) for people who feel that this increased amount could be beneficial. It is worth pointing out that very high levels of supplementation (over 100 micrograms or 4,000 IU daily) could certainly be unhealthy and is not recommended2.Vitamin D is not like the water soluble vitamins which are sometimes taken in very large amounts. It can seem instinctive to believe that if a small amount of vitamin D is beneficial, a larger amount must surely be even better. This might be true up to a certain level, but only within limits. Unless your doctor has advised otherwise, there is no good reason for most people to take more than 100 micrograms (4,000 IU) of Vitamin D per day. Eating processed foods which are already supplemented with vitamin D, such as many breakfast cereals, will add to your daily intake. However the levels in these foods are at a minimal level and insignificant when considering these maximum levels of supplementation.

  1. National Institutes of Health factsheet
  2. Harvard Medical School Vitamin D
  3. British Nutrition Foundation - New advice on vitamin D

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