My hairdresser recently told me that she was feeling very low in energy and after tests the doctor said this is due to vitamin D deficiency. The National Diet and Nutrition Survey suggests that 25% of 19 - 24 year olds and 1/6 th of the total adult female population are at risk of vitamin D deficiency. Most people are aware that vitamin D is produced following exposure to summer sunlight but in the winter, we are not exposed to the frequency of sunlight needed to produce vitamin D. So where do we get vitamin D during winter time if we don't have time or money to travel to the southern hemisphere? Good question and I'll see if we can figure it out from reading relevant documents including SACN update on vitamin D, NICE review on implementing vitamin D guidance (due out June 2014). First off...
What do we need vitamin D for?
- Absorb calcium from the intestine and to support skeletal development and bone health (this continues throughout adult life)
- Regulate the synthesis of PTH - parathyroid hormone which also plays an important role in maintaining calcium through production of active vitamin D
- Interact with VDR (vitamin D receptor) present throughout the body including small intestine, colon, T and B lymphocytes, brain, heart, gonads, prostate and breast. Researchers are investigating why this interaction takes place and the roles vitamin D has throughout the body
- (potentially) Support cell differentiation (i.e. when cells develop specific functions), cell proliferation (when cells with a unique/specific function multiply) and immune function
If the above sounds complicated, the key is to remember that vitamin D which is produced through exposure to the summer sun is required for skeletal development and bone health and is likely to have a role in a number of other important functions in the body.
What happens during the winter months?
The evidence suggests that between October and April we obtain vitamin D from the body stores accumulated during the summer and dietary sources including eggs, fish and enriched products like margarine and cereal. It is difficult to obtain vitamin D from dietary sources so it is important to stock up on sun over the summer.
What happens if we don't get enough vitamin D?
Severe lack of vitamin D is associated with rickets and osteomalacia (in adults and children). Long term conditions associated with lack of vitamin D may also include osteoporosis, cancer and diabetes. Rickets and osteomalacia are reported rarely in the UK but there is 'significant incidence' in UK based South Asian and African Caribbean populations.
According to the guidance we only need exposure for 5 - 15 minutes a day of summer sun but of course, after this it is important to cover up. Those of us with darker skins may need more exposure and this is currently being investigated.
So what shall we do now that summer is over?
Current guidance suggests that exposure to summer sun will provide enough vitamin D for the winter months. However groups at risk of vitamin D deficiency have been identified and include
- Pregnant and lactating women
- People over the age of 64
- Children under the age of 5
- People who do not go out during the summer months or are completely covered up by clothing
If you fall into these groups then supplements are advised to reach the RNI set by the Department of Health. Your health visitor or GP can provide advice in relation to this. Some groups may receive prescriptions.
Is the guidance changing?
SACN is currently reviewing the RNI for vitamin D set in 1991. NICE is currently producing guidance to encourage health professionals to raise awareness of the importance of vitamin D and encourage use of supplements in at risk groups. This includes all of the groups highlighted above as well as people with darker skin whose bodies do not make as much vitamin D as people with lighter skins. The guidance will be published next year.
So do I need to worry?
Not unless you fall into one of the at risk groups in which case it is definitely worth speaking to your health professional if they haven't already spoken to you. It is important to find out what supplement to take from a qualified health professional. For example most commercially available supplements are not suitable for pregnant women who may be able to access 'Healthy Start.'
Vitamin D is unique but like other vitamins it plays an important role in the body to prevent disease and maintain health. Nutrients don't work alone and it is important to achieve a varied and balanced diet for optimum health.
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