Contrary to popular belief, omega-3 supplements did not slow cognitive decline in older people participating in a large clinical trial by US National Institutes of Health researchers. Four thousand patients (58 per cent female) aged 72 years old on average were followed over five years. They were randomly split into four groups, receiving either a placebo, an omega-3 supplement, lutein and zeaxanthin (nutrients found abundantly in green leafy veggies), or omega-3 and lutein/zeaxanthin supplements. Participants were tested on their immediate and delayed recall, attention and memory, and processing speed at the start of the study and at two and four years later. Test scores of each subgroup fell to a similar extent over time, indicating that no combination of nutritional supplements made a difference. Omega-3 fatty acids are concentrated in fish oil and omega-3 supplements are often labelled as supporting brain health. Lenore Launer, one of the study's investigators, says: "It may be, for example, that the timing of nutrients, or consuming them in a certain dietary pattern, has an impact. More research would be needed to see if dietary patterns or taking the supplements earlier in the development of diseases such as Alzheimer's would make a difference."

Firstborn women are more likely to be overweight or obese as adults than their second-born sisters, finds the largest study of its kind on women. The researchers, from the University of Auckland in New Zealand and Sweden's Uppsala University, analysed data from the Swedish birth register. They focused on the time period 1991-2009 for women who were at least 18 years old at the time of their first pregnancy, and who had been born to a mother who was similarly at least 18 years old at the time. Based on about 29,000 subjects, the researchers found that firstborns were very slightly lighter than their second-born sisters at birth. But as adults during their first three months of pregnancy, their BMI was marginally higher (2.4 per cent) than that of their second-born sisters. They were also 29 per cent more likely to be overweight and 40 per cent more likely to be obese than their second-born sisters. And they were marginally taller (1.2 mm). The researchers surmise that the steady reduction in family size may be a contributing factor to the observed increase in adult body mass index worldwide among both men and women.