Vitamin D has been in the news recently. After years of being told to stay out of the sunlight because of the risks of skin cancer, now health professionals are concerned with the rise of people suffering from vitamin D deficiencies and even rickets, a disease that affects bone formation caused by a lack of vitamin D and calcium.
Vitamin D is known as a steroid vitamin. This belongs to a group of soluble prohormones which help with the absorption and metabolism of calcium and phosphorous. Vitamin D is not a simple single vitamin but actually comes in five forms - vitamins D1, D2, D3, D4 and D5. The forms that matter most for humans are vitamins D2 (ergocalciferol) and D3 (cholecalciferol) and these two vitamins are the usual ones used in the vitamin D nutritional supplements sold in pharmacies.
Sunlight helps the development of vitamin D in the skin and medical advice is that most people who are exposed to normal levels of sunlight do not need any supplements. The usual guidance is that a human needs around 10 to 15 minutes of sun exposure to the face, arms, hands or back without sunscreen with a greater than 3 UV index at least twice a week to generate adequate levels of vitamin D.
However, that is not as easy as it sounds. UVB rays vary greatly depending on cloud cover, latitude and the time of year. Above 42 degrees north latitude, the sun’s rays are unlikely to provide adequate levels of vitamin D from November through to February. Even the south coast of the UK is above this level - Portsmouth for instance is 50 degrees north - so during our winter few of us are likely to receive adequate vitamin D levels from sunlight alone.
A deficiency in vitamin D is increasingly thought to have effect on a number of other health areas and current research is looking at:
- Cancer. There is research being undertaken on the use of vitamin D to help stop the growth and progression of cancer cells.
- Obesity. Research is showing that vitamin D deficiency can interfere with the hormone leptin, which signals our brain to tell it we are full and should stop eating.
- Hormonal problems. Vitamin D may influence a number of functions including insulin, rennin, serotonin and estrogen. These hormones are involved in conditions such as blood pressure control, diabetes and heart disease.
- Immune system. Vitamin D may help to strengthen the immune systems and play a part in autoimmune disorders such as multiple sclerosis.
-Osteoporosis. Vitamin D should be able to assist in the prevention of fractures associated with this disease.
So if vitamin D is so important, how can we measure it and how can we improve our levels? Well, guide lines have now been set down to give a general indication of vitamin D requirements. These include a suggestion of 600 international units daily for people up to the age of 70 and 800 international units daily for people over 70.
Along with sunlight, food can help with the intake of vitamin D but it is difficult to obtain adequate levels just from diet. 3.5 oz of cooked salmon or mackerel will provide around 350 international units of vitamin D; 3.5 oz of liver provides just 15. A tablespoon full of cod liver oil provides over 1000 international units.
Knowing how much vitamin D you are getting is not a simple process because even if you are taking supplements of vitamin D, there is no guarantee that your body is absorbing the required levels. A doctor can offer a vitamin D test, this is done through a blood sample.
The general thoughts are that if you get outside quite a bit and eat normally, you should be fine regarding your levels of vitamin D. But this is hardly an exact science and if you have any concerns then ask your doctor.
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