Vitamin D & Sunlight Exposure
Related Sections : Suntan & Sunburn :
Vitamin D Is Produced From Sunlight
Vitamin D is produced by the action of sunlight on the skin where the UV B part of ultra-violet light converts vitamin A to vitamin D. This is the body's main source of vitamin D as very little is found in the diet.
In the UK there is not enough sunlight for about six months of the year to produce any significant amounts of vitamin D. This is worse in the north and better in the south. UV A, responsible for most tanning and skin aging, penetrates the atmosphere more easily and so is present throughout the year during daylight hours. UV B, responsible for vitamin D production, penetrates the atmosphere poorly, and so the sun need to be high in the sky for significant amounts to get through. This only happens in the UK during the summery six months of the year from about 10am to 4pm, and something like a ten minute exposure for your face and arms is all that you need.
Darker skin colour produces less vitamin D as skin pigmentation acts as a protective filter for UV light. So people with sun tans and darker skins need to expose their skin for longer to produce the required levels of vitamin D.
We get very little vitamin D from foods, because the ones containing vitamin D are the ones we do not eat regularly, such as liver, animal skin and fat, eggs, shell fish, oily fish. Good sources of oily fish includes salmon, trout, herring, sardines, pilchards and kipper. Also mackerel and fresh tuna (not tinned), though these are more heavily contaminated with mercury, which limits the amount you are recommended to eat. Oily fish are rich in vitamin D because it is fat soluble and stored in the fatty tissues of the body.
Protecting Ourselves From Sunlight Can Increase Our Risk Of Cancer
We are being encouraged to protect ourselves from sunlight to minimise our chances of developing skin cancer. This is the SunSmart advice from Cancer Research UK, whose aim is prevent us getting sunburn, which is a risk factor for skin cancer, and is a serious concern in the UK as many people are not SunSmart, and expose themselves to too much sun when it does appear, especially on holiday. This is not a healthy thing to do. Building up your sun exposure is much more sensible, as this is also the best way to build up a suntan, which gives some protection against burning. Little and often is best for sun exposure, and the length of time to expose yourself varies with your skin type and colouring, If you burn you have overdone it.
Many people are overdoing this protection and becoming fearful of the sun. People are coming back from sunny holidays as pale as when they went. Children are not being allowed to play outside or totally covered in suntan lotion all the time. There is also a tendency to live more of our lives inside. This has lead to generally low levels of vitamin D in the body, and an increase in rickets in children. Adults are little better. Vitamin D production from sunlight also decreases as we age, it has been suggested that a 70 year old can only produce a quarter of the vitamin D than a 20 year old for the same amount of sunlight.
Vitamin D deficiency increases the risk of many cancers, including breast, prostate and bowel cancer, so reducing exposure to sunlight can increase the chance of getting cancer.The risk of low vitamin D levels has been thought to be related to about 40-50% of cancers, putting it at a higher risk factor for cancer than smoking. So with the current balance of reduced sun exposure is probably causing an increased risk of cancer. We are certainly reducing the risk of skin cancer, but increasing our risk of other cancers by a much larger factor. (See Ref 2 -Vitamin D & Cancer Prevention - Dr. Wes Youngberg - YouTube Video). Low levels of vitamin D are also associated with many other diseases and health problems.
Recent research shows that the increase in melanoma is due to a change in diagnosis, with many more non-cancerous growths now being included in the diagnosis than before. The areas of skin where melanomas occurs is also increasing in areas not normally exposed to sunlight. It is also indoor workers, rather than outdoor workers exposed to sunlight who are increasingly being diagnosed with melanoma, indicating that exposure to sunlight can have a protective effect. (Ref 6, 7 & 8)
As with most things in life, we need to get this balance right.
Vitamin D Levels
The recommended Daily Amount (RDA) for vitamin D is currently set far too low at 5 micrograms or 200 IU a day, and is based on the amount needed to prevent rickets. However, vitamin D is so essential for the body that nutritionists generally consider that much more is needed for optimum health. Research on vitamin D has exploded recently, and it has been shown to have a very wide variety of important functions in the body, and a low level of vitamin D has been shown to cause a large number of health problems, such as reduced immune function making us susceptible to colds and flu during the winter, and increased breast, prostate and colon cancer. It may also be linked with bone fractures caused by osteoporosis, and some chronic diseases such as diabetes and multiple sclerosis.
A more realistic daily allowance is 2,000 IU a day, on top of what you are getting from diet and sunlight. After all, a fair-skinned person with about 80% of their skin exposed to the sun for 20 minutes at mid-day in the UK summer can produce about 10,000 IU with no harm at all. Higher doses have also been recommended. (Ref 1).
High doses of vitamin D can be toxic, but these levels are generally considered to be safe unless there is any medical reason for you not taking them. It is recommended to have your vitamin D levels periodically checked by your doctor if you are taking vitamin D supplements above the recommended daily allowance of 5 micrograms (200 IU), though NHS Choices (Ref 3) considers taking a supplement of 25 micrograms (1,000 IU) a day to be safe.
SAD (Seasonal Affective Disorder) is associated with low exposure to sunlight, and may be linked to low levels of vitamin D in the winter.
Tanning beds may be one answer to increasing our winter exposure to UV B, but not all tanning beds are considered safe and some have received unfavourable reviews due to the low amount of UV B and the high amount of UV A, which tans, but does not produce vitamin D.
Vitamin D Supplements
Vitamin D supplements are often recommended to be taken daily through the winter, and even through the summer where the skin is not being exposed to adequate amounts of sunlight. Cod Liver Oil also contains vitamin D in lower doses than are needed, though it is a useful source of vitamin A.
- Vitamin D - You Are Almost Certainly Not Getting Enough - Patrick Holford
- Vitamin D & Cancer Prevention - Dr. Wes Youngberg - YouTube Video
- Vitamin D - NHS Choices
- Rickets On The Rise - NHS Choices
- Sun CAN Actually Help Protect You Against Skin Cancer - Mercola
- Melanoma epidemic: a midsummer night's dream? - Br J Dermatol. 2009 Sep;161(3):630-4. Epub 2009 Jun 9
- The Surprising Cause of Melanoma (And No, it's Not Too Much Sun) - Mercola, 2011 Nov
- Is there more than one road to melanoma? - The Lancet, Volume 363, Issue 9410, Pages 728 - 730, 28 February 2004