Ethnic differences in people's levels of so-called good cholesterol, or HDL, may be due to diet - particularly carbohydrate intake - as much as genes, a Canadian study has found. Chinese, for example, typically eat few carbs and have high HDL levels, whereas South Asians consume a lot of carbs and have low HDL levels, according to the Population Health Research Institute study. Consuming sugar-sweetened soft drinks, juices and snacks is linked to lower HDL levels, Reuters reports.

Rise in cigarette nicotine levels

Nicotine levels in cigarettes have risen by 11 per cent since 1998, according to a Harvard School of Public Health analysis that supports an earlier study by Massachusetts health officials - but tobacco industry officials deny there has been a deliberate attempt to boost concentrations of the addictive ingredient, WebMD reports. Team leader Gregory Connolly says that, even allowing for yearly fluctuations due to inconsistencies in crops, 'there was a significant increase in nicotine levels on the order of 1.6 per cent per year'.

Larger families prone to cancer

People from large families have a higher risk of developing stomach cancer - with younger siblings most at risk, a 28-year study of more than 7,000 Japanese-American men has found. About 50 per cent of the world's population carry strains of the Helicobacter pylori bacteria, which is linked to peptic ulcers and stomach cancer, healthday.com reports. Men who have the bacteria and had seven or more siblings are twice as likely to develop stomach cancer than those with one to three siblings, the New York University Medical Centre study found. Team leader Martin Blaser says the bacteria may become more virulent in younger siblings. 'That early childhood events affect the risk of cancers occurring in old age is remarkable,' he says.

Active women beat off fibroids

Regular exercise may help prevent uterine fibroids - benign tumours that can cause infertility, bleeding, pain and pregnancy difficulties, and are a major reason for hysterectomies. A study of more than 1,100 women by the National Institute of Environmental Health Sciences in North Carolina found more active women were less likely to have fibroids. Those who exercised for seven hours or more a week had a 40 per cent lower fibroid risk than those who exercised for less than two hours, Reuters reports. And those who exercised vigorously for at least four hours a week were less likely to develop tumours.

Hefty cost of weight gain

Carrying excess poundage can significantly cut wages, particularly for men - although it's not clear if this is because of discrimination or health problems that may limit productivity, an Italian study has found. A 10 per cent increase in body mass index (BMI) can cut a man's earnings by 3.3 per cent and a woman's by 1.8 per cent, say University of Padova researchers, who based their work on European Commission data. The effect was most marked in so-called oil belt countries such as Spain, Greece, Italy and Portugal, Reuters reports. There was no significant difference in beer belt nations such as Austria, Ireland, Denmark, Belgium and Finland. 'There's an income gradient which relates to obesity in the same way that other factors do,' says team leader Giorgio Brunello.

X marks brain's selfless spot

Scientists have pinpointed the part of the brain associated with altruism - and it's not where they thought it would be. 'We went into this experiment with the idea that altruism was really a function of the brain's reward systems - altruistic people would simply find it more rewarding,' says team leader Scott Huettel of Duke University. Instead, altruism is associated with the posterior superior temporal cortex, which focuses on perceiving others' intentions and actions, healthday.com reports. Altruism is puzzling because it doesn't seem to provide any survival edge. The researchers say it appears to be a primitive form of empathy.

Jason Sankey is a tennis professional