Find out the effects of Vitamin D on your body

Vitamin D is most well-known for its role in bone health as it facilitates calcium absorption. However, modern research is highlighting that vitamin D is also involved in many other areas of our health, especially in cardiovascular, immune and psychological health.

Natural Production of Vitamin D

Vitamin D can be made by our bodies when our skin is exposed to sunlight. The amount of vitamin D we make depends on our age, how much skin is uncovered, the length of sun exposure, our skin tone and whether or not we are using sunblock. Living in the UK we may only get enough radiation from the sun for vitamin D production between May and October.

We can obtain some Vitamin D from our diet but it is only present in any significant amounts in oily fish and eggs. The amounts available from diet, however, are tiny in comparison to the amount that our bodies make from sunlight. A serving of fresh wild salmon contains approximately 988iu of vitamin D, a serving of farmed salmon 240iu and a serving of mackerel just 24iu. However, without sunscreen and with arms and legs exposed, our skin will make 10,000 to 15,000 units of vitamin D in one sun exposure, on average. However, sunscreen with an SPF of more than 15 blocks 100% of vitamin D production in the skin.

It’s a tricky situation as we need to be mindful about skin cancer and yet the extensive use of sunblock and the fact that people tend to spend less time outside are thought to be partly responsible for such widespread Vitamin D deficiency. This is why testing and supplementation (if required) is so important.

Effects of Vitamin D deficiency

According to the National Diet and Nutrition Survey up to 90% of the UK population have sub optimal vitamin D levels. The following conditions have been associated with low vitamin D levels:

Severe deficiency:

Risk of rickets

Increased risk of colon cancer


Calcium loss from bones increasing the risk of osteoporosis

Poor wound healing

Increased muscle pain

Joint and back pain



Increased risk of schizophrenia


Autoimmune disease



Painful periods

Suboptimal levels:

Increased risk of heart attack

Increased incidence of high blood pressure

Increased risk of multiple sclerosis

Suboptimal levels:

Increased risk of heart attack

Increased incidence of high blood pressure

Increased risk of multiple sclerosis

Particular Risk Factors for Vitamin D Deficiency

Dark skin:

People with dark-coloured skin synthesize less vitamin D on exposure to sunlight than those with light-coloured skin. The risk of vitamin D deficiency is particularly high in African and Asian people living in the UK.


The elderly have reduced capacity to synthesize vitamin D from sunlight and are also more likely to stay indoors. Institutionalized adults who are not supplemented with vitamin D are at extremely high risk of vitamin D deficiency.

Covering all exposed skin or using sunscreen whenever outside:

Sunscreen with an SPF factor of 8 reduces production of vitamin D by 95% and sunscreen with an SPF of more than 15 blocks 100% of vitamin D production in the skin.


Apart from fortified foods and drinks the only dietary sources of vitamin D are found in animal foods so vegetarians may be at risk of deficiency, particularly if sunlight exposure is insufficient or is sun screens are always used when outside.

Body weight:

Research has shown that higher body mass increases the risk of vitamin D deficiency.


Ideally your vitamin D levels should be tested to determine whether you need vitamin D supplements and the dose that you will require.

Your GP may be able to arrange vitamin D testing free of charge in certain circumstances. For example, if you are suffering from osteoporosis, autoimmune disease, depression or if you are pregnant or breastfeeding.

Alternatively testing is available for £25.00 from City Assays. This is a simple blood spot test which can be carried out at home. You then post the test sample back to the laboratory and your results are emailed to you. For more information or to request a test: Tel: 0121 507 4278


Vitamin D may interfere with certain medications so it is important to consult your GP, Pharmacist or Nutritionist before taking a vitamin D supplement if you are taking prescription medication.

People with hyperparathyroidism should not take vitamin D without consulting a GP and people with sarcoidosis, tuberculosis, Lyme disease, lymphoma, or kidney disease should not supplement with vitamin D, unless a doctor has determined that their calcium levels are not elevated.

What to do if you are deficient

If you would like personalised vitamin D supplementation recommendations based on your test results you can email your results to and make an appointment for a consultation.

If your results show that you have a severe deficiency or if you are suffering from certain medical conditions you may be referred to your GP.

Rechecking Your Vitamin D Level

It is recommended that you have your vitamin D level rechecked within 2 months after starting supplementation, depending on your health condition.

Tanya Artus is a qualified and registered nutritional therapist and homeopath. She practices from Southbourne Physiotherapy clinic in Westcliff-on-Sea. For more information or to make an appointment with Tanya call 0793 253 5929, visit or email


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