βCarotene protects laboratory mice from skin cancer, but hopes that it might do the same for people are fading. A secondary analysis of data from the physicians health study, a large randomised trial, shows that taking β carotene every other day for 12 years does not protect male doctors against non-melanoma skin cancer (Archives of Dermatology 2000;136:179-84). A useful reminder, remarks one commentator, that scientists should resist making health recommendations on the basis of a few observations in laboratory animals.

Data from the same trial surface in another recent paper, this time examining the link, or lack of one, between exercise and reduced risk of prostate cancer (International Journal of Epidemiology 2000;29:29-35). Observations in this trial, which was set up to investigate something completely different, do not support the theory that because exercise can suppress androgens it might also protect against prostate cancer.

It's estimated that over a fifth of American women have problems with their libido. Testosterone may be the answer for some of them, although a recent Dutch study finds that they would have to wait up to four and a half hours for an effect (Archives of General Psychiatry 2000;57:149-53). Eight healthy …