Positive Health Online

Vitamin D is unique because in its active form it is actually a steroid hormone (calcitriol) rather than a vitamin. There are two forms: vitamin D2 which is from plant foods and D3 which is obtained from animal foods. We can also make D3 in the skin when exposed to UVB rays in sunlight, whilst D2 comes from dietary sources only.

Up until recently little attention was paid to this vitamin since it was generally believed that deficiency was rare and mainly limited to the elderly, pregnant and people from cultures where the skin is traditionally kept covered. Now vitamin D deficiency is a much discussed topic as it becomes evident that it is far more widespread throughout the general population. It is estimated that one fifth of adults in the UK are deficient in vitamin D. People with dark skin or of South Asian origin have a nine in ten chance of being deficient.

One reason for the increased deficiency is probably due to increased use of sun protection creams with a high SPF (over 15). Whilst the advice to avoid sunburn is sound, we have perhaps gone too far in our efforts to prevent skin cancer. Exposing bare arms, face and hands to sunlight for 15 minutes several times per week (more for darker skin) during April to September is recommended (the skin should never go red and individual sensitivity has to be taken into account), to prevent vitamin D deficiency. However in the winter, there is insufficient sunlight meaning dietary vitamin D and/or a supplement has to be relied upon.

The role of vitamin D in maintaining bone mineralization and the prevention of osteoporosis and rickets has been known for a long time. What is relatively new knowledge is vitamin D's wider physiological effects. It appears to be more important and powerful than was previously realized. For example, it plays a role in cancer prevention, immunity and autoimmunity, mood and depression, insulin regulation, muscle and joint health and blood pressure control.

If you suffer from any of the following conditions, it is well worth having your vitamin D status checked; osteoporosis/osteopenia, depression, fatigue, infertility or hormone related problems, PCOS, insulin resistance, diabetes, frequent infections, auto immune conditions (e.g. rheumatoid arthritis, MS), bone or muscle pain, fibromyalgia, chronic inflammation, heart disease, or a family or personal history of cancer. Also if you suffer from conditions affecting intestinal absorption such as coeliac or Crohn's disease, your vitamin D levels may be low. Pregnant and breastfeeding women are vulnerable to vitamin D deficiency since it is needed for the growth of the baby, so should also get checked. Breastfed babies need a 200 iu vitamin D supplement daily.

Food Sources of Vitamin D

1. D2: sunflower seeds, leafy greens, avocado, carrot;
2. D3: Mackerel, herring, salmon, liver. Cod liver oil is the richest source. Cottage cheese and eggs contain a smaller amount;
3. Some foods are fortified with D2 and D3, e.g. bread, cereals, yoghurt & milk.

How Much is Enough?

The current government recommended daily intake for adults of 400 iu (600 iu for those over 70) is now thought to be much too low and is being revised upwards. The EU scientific committee on food suggests 2000 iu as the upper safety limit for vitamin D intake. This is probably still over cautious as levels of up to 10,000 iu have been given in clinical practice without side effects. However it is essential to have your vitamin D levels tested and work with a practitioner if you are going to take the higher amounts which may well be necessary.

Your GP should be open to running a blood test for vitamin D, particularly if you have a history of osteoporosis in the family. Otherwise the test can be done privately via a practitioner; for example through a laboratory such as Genova Diagnostics. The normal parameters for vitamin D levels should be between 75-200 nmol/L. GPs usually prescribe 1000 iu daily to correct a deficiency. In practice I find at least 2000 iu daily is more effective if levels are 40 or below. Re testing in 6-8 weeks is essential to monitor the effectiveness of treatment.

If you have not been tested, 400-800 iu daily is a good maintenance intake. Biotics Research Bio- D-Mulsion is the brand I recommend and one drop will supply 400 iu. It also comes in a higher strength of 2000iu per drop (Bio-D-Mulsion Forte) ,so is very convenient, rather than taking lots of capsules. If you are taking the higher strength one you should do it under practitioner supervision and have your D levels monitored.

Vitamin D toxicity is relatively rare; however, excess will be stored in the body rather than excreted, unlike a water soluble vitamin such as vitamin C or B complex.

The main contraindication for supplementation is if you have a condition that results in high calcium levels in the blood. This may include an overactive parathyroid gland, kidney or liver disease, kidney stones, granulomatous disease, sarcoidosis, Lyme disease, lymphoma. Certain medications interfere with vitamin D absorption, including carbamezepine, phenytoin, primidone and barbiturates.

Further Information

Genova Diagnostics: www.gdxuk.net  
Biotics Research: www.nutri-linkltd.co.uk