I am trying to find a calcium/vitamin D3 supplement which does not contain hydrogenated oil. The information is not provided in direction leaflets. My GP suggests asking a pharmacist, but I get no clear answer. Are pharmaceutical companies obliged to declare whether an oil listed in ingredients is hydrogenated? How can I find a suitable product?

Dr Fred Kavalier answers your health question:

Pharmaceutical companies (and food supplement and vitamin manufacturers) use a variety of "non-medicinal ingredients" when they manufacture drugs. There are strict European regulations about what ingredients can be used. Companies are required to include all the ingredients (including the inactive ones) in the labelling of the drug. However, these regulations only apply to medicines.

At least four different oils are used in medicine manufacture: arachis oil (peanut oil), soya oil, castor oil and sesame oil. When soya oil is hydrogenated, the label should say "hydrogenated soya oil". When unhydrogenated soya oil is used, the label should say "soya oil".

Unfortunately, there is at least one product (Calcichew-D3) with hydrogenated soya oil that simply says "vegetable fat" on the label. You can look up a list of additional ingredients on the website of the electronic Medicines Compendium emc.medicines.org.uk. Now I have a question for you: why are you so concerned about swallowing tiny amounts of hydrogenated soya oil?

Please send your questions and suggestions to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax 020-7005 2182 or e-mail to health@independent.co.uk. Dr Kavalier regrets that he is unable to respond personally to questions.