Wednesday, December 29, 2010

Eating "healthier" means living longer (?)

The heading above is something of a tautology but there are some non-tautologous findings (below) underlying it. We also see below, however, more epidemiological speculation. And, perhaps sadly, the differences in relative risk (40%) are too low to support inferences of causation anyway (200% conventionally required). But let us look at what the findings COULD mean anyway:

Note that diet was assessed via a self-report questionnaire rather than direct observation. That leaves a lot of room for "faking good" and high IQ people (who are healthier anyway) may be more able and inclined to do that.

Note that high IQ has been found elsewhere to be a strong predictor of "good" (conforming) behavior: We read, for instance, that "The mother's IQ was more highly predictive of breastfeeding status than were her race, education, age, poverty status, smoking, the home environment, or the child's birth weight or birth order".

So the alleged enthusiastic eaters of fruit and vegetables (etc.) may simply be high IQ people saying what they know will earn approval. They may even actually eat a lot of fruit and vegetables, but we don't know that.

It could be objected that education was controlled for but the correlation between educational level and IQ is around .7 -- which leaves 50% of the variance in the two variables not explained by one another. Thus control for education may reduce the influence of IQ but certainly does not eliminate it.

And whether what is true of septuagenarians is true generally would also seem moot

The leading causes of death have shifted from infectious diseases to chronic diseases such as cardiovascular disease and cancer. These illnesses may be affected by diet. In a study published in the January 2011 issue of the Journal of the American Dietetic Association, researchers investigated empirical data regarding the associations of dietary patterns with mortality through analysis of the eating patterns of over 2500 adults between the ages of 70 and 79 over a ten-year period. They found that diets favoring certain foods were associated with reduced mortality.

By 2030, an estimated 973 million adults will be aged 65 or older worldwide. The objective of this study was to determine the dietary patterns of a large and diverse group of older adults, and to explore associations of these dietary patterns with survival over a 10-year period. A secondary goal was to evaluate participants' quality of life and nutritional status according to their dietary patterns.

By determining the consumption frequency of 108 different food items, researchers were able to group the participants into six different clusters according to predominant food choices:

"Healthy foods" (374 participants)
"High-fat dairy products" (332)
"Meat, fried foods, and alcohol" (693)
"Breakfast cereal" (386)
"Refined grains" (458)
"Sweets and desserts" (339).

The "Healthy foods" cluster was characterized by relatively higher intake of low-fat dairy products, fruit, whole grains, poultry, fish, and vegetables, and lower consumption of meat, fried foods, sweets, high-calorie drinks, and added fat. The "High fat dairy products" cluster had higher intake of foods such as ice cream, cheese, and 2% and whole milk and yogurt, and lower intake of poultry, low-fat dairy products, rice, and pasta.

The study was unique in that it evaluated participants' quality of life and nutritional status, through detailed biochemical measures, according to their dietary patterns. After controlling for gender, age, race, clinical site, education, physical activity, smoking, and total calorie intake, the "High-fat dairy products" cluster had a 40% higher risk of mortality than the "Healthy foods" cluster. The "Sweets and desserts" cluster had a 37% higher risk. No significant differences in risk of mortality were seen between the "Healthy foods" cluster and the "Breakfast cereal" or "Refined grains" clusters.

According to lead author Amy L. Anderson, Ph.D., Department of Nutrition and Food Science, University of Maryland, the "results of this study suggest that older adults who follow a dietary pattern consistent with current guidelines to consume relatively high amounts of vegetables, fruit, whole grains, low-fat dairy products, poultry and fish, may have a lower risk of mortality. Because a substantial percentage of older adults in this study followed the 'Healthy foods' dietary pattern, adherence to such a diet appears a feasible and realistic recommendation for potentially improved survival and quality of life in the growing older adult population."

The journal article is "Dietary patterns and survival of older adults" by Amy L Anderson et al., Journal of the American Dietetic Association, Volume 111, Issue 1 (January 2011)


Some brains are more sociable than others

If your social life leaves something to be desired, it might be your brain structure that’s to blame. A ‘Facebook feature’ deep in the temporal lobe governs the number of friends you are likely to make, scientists have found.

The amygdala, a small almond-shaped structure, has for some time been linked to empathy and fear responses. But a study suggests that the larger the amygdala, the wider and more complex is its owner’s network of friends and colleagues.

Volunteers aged between 19 to 83 were asked to complete questionnaires which measured how many regular social contacts they had, and in how many different groups.

Magnetic resonance imaging scans found a positive link between big amygdalas and the richest social lives. Professor Lisa Barrett, a psychologist at Northeastern University in Boston, Massachusetts, reported the findings in the journal Nature Neuroscience.

She said they were consistent with the social brain theory, which suggests the human amygdala evolved to deal with an increasingly complex social world. Other studies of primates have shown that those living in larger groups tend to have larger amygdalas.

The findings was published in a new study in Nature Neuroscience.

Dr Lisa Barrett, Professor of Psychology at Northeastern University, who took part in the research, said the amygdala got bigger to cope with mankind's more hectic social life.

She added: 'Further research is in progress to try to understand more about how the amygdala and other brain regions are involved in social behaviour in humans.'

Her colleague Dr Bradford Dickerson, an associate Professor of Neurology at Harvard Medical School said: 'This link between amygdala size and social network size and complexity was observed for both older and younger individuals and for both men and women.'


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