Folic acid is a vitamin which is particularly necessary for fast-dividing cells – which is why we use folate antagonists to kill bacteria and cancers. But it is still a bit of a shock to think that modest folic acid supplementation (1mg daily) might possibly encourage the development of colon cancer, as this paper suggests. It is only a possibility, but worrying given that many countries have begun to fortify flour with folic acid to prevent neural tube defects. A thousand patients with colorectal adenomas were randomised to receive folic acid or placebo and followed up with colonoscopy. At 3-5 years, the folate group had more adenomas and especially carcinomas though the difference lay on the border of statistical significance. What we can say with certainty is that folic acid is definitely not protective against colonic neoplasia.

I don’t suppose that many readers are regular users of rectal artemesinin derivatives (those in the USA can’t even get hold of them) but it’s good to know that where they will do the most good – i.e. in countries where advanced malaria is a common threat to life – they work very well, no matter which preparation is used (a review of 45 studies).

Does This Patient Have Dementia? asks the latest in the Rational Clinical Examination series. This is a leisurely stroll through what is known about dementia and how to screen for it. The best studied instrument is the Mini-Mental State Examination, but it is still under copyright. So if you want to know if you have dementia, you can measure the time it takes you to memorise the entire MMSE; and after that, you can use it legally. As a highly educated person who drinks regular alcohol and takes exercise, you will probably score quite well.