Brighter people live longer, says Glasgow scientist David Batty

Yet more evidence that high IQ is usually a part of general biological fitness

Greater intelligence may in part partially explain why people from a high socio-economic background live longer than those of lower social status, researchers have suggested. A study of former soldiers in the United States has indicated that differences in IQ may explain almost a quarter of the differences in mortality between people of higher and lower social classes.

It has long been accepted that social status affects mortality, with a particular influence on death from cardiovascular events such as strokes and heart attacks. Many of these differences have been ascribed to stress, to income, and to behavioural factors such as smoking and diet — but these cannot explain the whole gap in longevity between the highest socio-economic groups and the lowest ones.

The new study, from a team led by David Batty, of the MRC Social and Public Health Sciences Unit at the University of Glasgow, compared outcomes from a group of 4,289 former American soldiers drawn from diverse social backgrounds. It found that variations in IQ explain about 23 per cent of the survival differences between different social groups. Details of the study are published in European Heart Journal.

Professor Sir Michael Marmot, of University College, London, who leads the Whitehall II study of civil servants, which has uncovered many of the effects of social class on mortality, and his colleague Mika Kivimaki, offered three possible explanations for the effect in a commentary for the journal. [The Marmot is associated with the dubious WCRF and some equally dubious dietary claims so his interpretations should be treated with caution]

“Intelligence might lead to greater knowledge about how to pursue healthy behaviours,” he wrote. Intelligence may “cause” socio-economic position; that is, more intelligence leads to more education, and greater income and occupational prestige. “Intelligence may be a marker for something else, and it is that something else, early life exposures, for example, that leads to mortality,” Dr Batty said.

“We already know that socio-economically disadvantaged people have worse health and tend to die earlier from conditions such as heart disease, cancer and accidents. Environmental exposures and health-related behaviours, such as smoking, diet and physical activity, can explain some of this difference, but not all of it. This raises the possibility that as-yet-unmeasured psychological factors need to be considered. One of these is intelligence or cognitive function, commonly referred to as IQ. This measures a person’s ability to reason and problem-solve. IQ is strongly related to socio-economic status.

“IQ wasn’t a magic bullet in this study, but this psychological variable had additional explanatory power on top of the classic variables such as smoking, high blood pressure, high blood glucose and obesity. It has partially explained the differences in death from heart disease and all causes.”

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Grapefruit again

Women have long used grapefruit in dieting but I have never quite understood why or how. We now read however that grapefruit 'makes liver burn fat instead of storing it' (in overfed laboratory mice). So maybe there is something in it after all

The humble grapefruit could prove to be a mighty - if bitter tasting - weapon in the fight against diabetes, scientists say. A study found naringenin, a flavonoid found in citrus fruit, makes the liver burn fat instead of storing it after a meal. Researchers believe the chemical would also help obesity sufferers and even fight diabetes, because it also helped balance insulin and glucose levels.

Naringenin gives citrus fruit, in particular grapefruit, its bitter taste. But since the tests involved far higher doses of naringenin than those found naturally in the fruit, anyone interested in its fat-busting benefits will have to wait for scientists to develop a concentrated supplement. Once available, it could help treat patients suffering from Type 2 diabetes, a main cause of heart disease.

The tests were carried out on mice by a team at the Robarts Research Institute at the University of Western Ontario, in Canada, and published in the journal Diabetes. Two groups of mice were both fed the equivalent of a Western diet to speed up their ‘metabolic syndrome’ - the process which leads to Type 2 diabetes in humans. One of the groups ate food that had been treated with naringenin. The non-naringenin mice became obese, their cholesterol levels rose and their bodies became resistant to insulin, a hormone that regulates blood sugar levels.

The mice given the chemical did not suffer from these ailments, despite eating identical diets to the others. Any rise in cholesterol-was corrected by the naringenin which also ‘reprogrammed’ their livers to burn fat rather than store it.

Lead researcher Professor Murray Huff added: ‘Furthermore, the marked obesity that develops in these mice was completely prevented by naringenin. ‘What was unique about the study was that the effects were independent of calorific intake, meaning the mice ate exactly the same amount of food and the same amount of fat.’ The team will now try to develop the chemical into a treatment for humans.

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