Vitamin D is a hormone essential for many functions in the body. The most well known is for bone health. Deficiencies can lead to diseases such as rickets and osteoporosis.
More recently it has become apparent that people who have low vitamin D levels may be at increased risk of other serious diseases such as multiple sclerosis, diabetes and cancers such as breast, bowel, prostate and lymphoma amongst others.
Studies have shown that those patients diagnosed with melanoma in summer do better than those diagnosed in winter and it has been postulated that this is because the increased vitamin D levels during summer help the body fight cancer.
Vitamin D has been shown to prevent flu in winter to a similar degree to the flu vaccine. Vitamin D has also been shown to be low in children with autism.
The deficiency of vitamin D can lead to localised or generalised bone and muscle pain and should be checked in patients with these symptoms. Muscle weakness leading to a fall is another symptom of vitamin D deficiency, especially in the older population. In association with thin bones due to osteoporosis, this can be deadly.
Sources of Vitamin D
Usually, vitamin D is made in the skin in response to the sun’s UV rays. However, vitamin D deficiency is becoming much more common as the anti-skin cancer message spreads. Sun-screen blocks out the UV rays too well!
Some recommend that the best way to get enough vitamin D is to expose a large part of the body for a very short period (not enough to burn) in the middle of the day. Getting exposure at the end of the day is not sufficient as the UVB rays necessary for vitamin D production do not reach the earth when the sun is lower in the sky.
Additionally, as one gets older, the production of vitamin D in the skin stops, which is why people over the age of 70 are susceptible to vitamin D deficiency and potential bone and other problems.
Very few foods other than cod liver oil have enough vitamin D to supplement one’s diet naturally so vitamin supplementation is recommended. The problem with cod liver oil is that this has a very high level of vitamin A which can be dangerous in high levels (unlike vitamin D).
How much Vitamin D do I need?
To have the best effect, blood vitamin D levels should be right near the top of the normal range (above 80-100 nmol/L). For many years the recommended amount for vitamin D was between 400-1,000 IU/day. Nowadays, it is more appreciated than supplementation of between 2,000 and 5,000 IU may be required.
Unfortunately, in Australia, only 1,000 IU tablets/ capsules are available over the counter at health food stores and chemists. Compounding pharmacies can make up higher doses with a doctor’s prescription. Blood levels should be checked when starting supplements, after three months and then annually.
Vitamin D in children
Some studies have shown that vitamin D deficiency is becoming more prevalent in children and adolescents. It may be a good idea to check the blood levels in the younger age group occasionally.
Measuring Vitamin D
Different laboratories use different ranges for vitamin D but most normal ranges are from about 25-140 nmol/L. It’s probably best to aim for a target range of above 80-100 nmol/L, rather than be satisfied with a level in the low end of the normal range.