The results of two large, long term, placebo controlled trials of the effect of β carotene supplements rule out the much debated possibility that these supplements have any impact on the incidence of malignancy or cardiovascular disease (New England Journal of Medicine 1996;334:1145-55). As the accompanying editorial states, they send a clear message that “the tens of millions of dollars spent annually on beta carotene supplements should now be diverted to more useful purposes.”

No gold standard exists for diagnosing asthma. Research in children in Denmark reported in “Thorax” (1996;51:503-9) found that methacholine provocation performed best in terms of estimated predictive values and sensitivity but that measurement of the peak expiratory flow added another 14-18% to the proportion of people who probably had asthma. The two tests seem to identify different types of abnormality in the airways.

The negative effect of smoking on fecundity was clearly shown in a study of 4000 couples (American Journal of Epidemiology 1996;143: 578-87). The median time taken to achieve a pregnancy was 2.6 months in women who did not smoke but 4 months in those who smoked more than 10 cigarettes a day.

The lower the diastolic blood pressure, the better the health prospects for young and middle aged people; but for older people the …