What is Vitamin D?

This is the vitamin that is made in your skin when you are exposed to the sun. Some foods (such as oily fish) contain a little vitamin D, and you can also get it from taking cod liver oil and other supplements. It is particularly essential for regulating the amount of calcium and phosphate in the body as well as good overall health.

Why is this study being carried out?

We get most of our vitamin D from sunshine. Our summer weather in the UK is unreliable, and often we don’t get much sunshine. It has been suggested that older people might reduce the risk of several common diseases (ranging from cancer and heart disease to flu) by taking a high dose vitamin D supplement. However, the available evidence on vitamin D and health is inconclusive, and we want to find out if there really is any benefit by carrying out a large, well designed study.

Why have I been invited?

If you have been invited to participate in the trial, it is because you satisfy our screening criteria as a potentially eligible participant. You will have been sent an invitation letter, information booklet and reply slip. Please read the information booklet carefully and only return the slip if you are interested in taking part.

Do I have to take part?

No, you do not have to take part. Participation in the trial is completely voluntary and unpaid. Even after you have signed the consent forms, you are still free to withdraw from the study at any time without giving a reason.

What will I have to do?

  • You will attend your local GP practice twice (once at the beginning of the study and once at the end of the study). At each visit you will give a blood sample and answer some questions about things that affect your vitamin D level.
  • You will receive one telephone call 3 weeks after your first visit to the GP practice to confirm your eligibility for the study and ask if you are still willing to participate.
  • You will take 24 doses of the study supplement (or nothing if you are assigned to open control) – one dose of oil each month for two years. All of the doses will be taken at home.
  • You will be reminded once a month to take the study supplement via your choice of either telephone call, e-mail or text
  • You will be contacted once every 3 months (by your choice of post or email) to check that you have taken your study supplement and to ask about your health. (see QFU section for more details)

What are the side effects and risks of taking part?

Participating in this trial is very low risk. Rarely, people may develop raised levels of Calcium in the blood when taking vitamin D. The risk of this happening to you in this study is less than 1/400. Stopping vitamin D and taking simple rehydration is almost always effective in returning Calcium levels to normal, but medication can also be used to normalise Calcium levels if necessary.

Symptoms of raised Calcium levels include, nausea, vomiting, thirst, passing excessive amounts of urine or feeling generally unwell. If you develop any of these symptoms, please contact your GP to discuss your symptoms.

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