Wednesday, November 07, 2007

The breastfeeding crusade continues

Whoopee! A study that DOES consider social class. Sometimes lots of nagging does get results. It seems reasonable that breast is best -- if the mother finds it easy -- but proving it is another matter. Since social class is likely to influence who breastfeeds, it is important to separate out class effects from effects of feeding per se. The study below uses education as a proxy for class -- which is a good start. But education does not correlate strongly with other class indices -- and even the link to IQ usually covers only about 50% of the variance -- so the question still invites the old Scottish verdict of "not proven".

Another reason for skepticism is that the incidence of breast feeding was assessed by self-report rather than by observation. That invites a whole range of possible distortions. It is undoubted that some mothers might for various reasons distort the amount of breastfeeding they did -- and what are the characteristics of such women? I could go on to multiply hypotheses -- particularly with reference to the fact that breastfeeding was rather out of fashion at the time the adults concerned were born -- but what's the point? We just have an unknown

Breast-fed babies are less likely to be obese or have heart disease in later life than those who were bottle-fed, say researchers. In a large US study, middle-aged adults who were breast-fed as infants were found to be 55 per cent more likely to have high levels of high-density lipoprotein (HDL), the so-called "good" cholesterol that protects against cardiovascular disease (CVD).

They also had a lower average body mass index (BMI) score - 26.1 kg/m2 compared with 26.9 - than those who were not breast-fed. A BMI score of more than 25 is considered to be overweight and a risk factor for heart disease. "This was a modest reduction in BMI, but even a modest reduction leads to a significantly reduced risk of cardiovascular disease-related death," the researchers say.

The study, reported yesterday at a meeting of the American Heart Association in Orlando, Florida, included 393 mothers enrolled in the continuous Framingham Offspring Study and 962 of their offspring. The average age of the offspring was 41 and 54 per cent were women. Although previous studies have hinted that breast-feeding produces health benefits in later life, much of the existing research was limited by a lack of adjustment for other factors, such as socioeconomic status.

Britain has one of the lowest breast-feeding rates in the industrialised world. Initiation rates currently stand at 76 per cent, meaning that a quarter of infants receive no breast milk at all.

Nisha Parikh, who led the latest study at the Beth Israel Deaconess Medical Centre, in Boston, Massachusetts, said that having been breast-fed in infancy was associated with longer-term health benefits "even after accounting for personal and maternal demographic and CVD risk factors that could influence the results". Research also suggests that babies who are not breast-fed have a higher risk of infection.

Dr Parikh said that she had the idea for the study after returning from maternity leave. "The benefits of breast-feeding in infancy and childhood are well established. But I wondered if it were as helpful for health in adulthood," she said. For the study, mothers reported whether they breast-fed each of their children and for how long. Overall, 26 per cent of the participants' offspring were breast-fed.

After adjustment for factors including use of blood-pressure-lowering medication, maternal education, smoking and body mass index, breast-fed offspring had higher than average HDL-cholesterol levels in adulthood: 56.6 mg/dL compared with 53.7 mg/dL for the bottle-fed participants. HDL bonds with and transports cholesterol particles in the blood stream, and as such protects against heart disease and stroke by preventing blood vessels from becoming blocked and furred up (atherosclerosis). Lower HDL-borne cholesterol levels are known to increase the risk of heart disease.

"The findings show that early environmental exposures have long-term health effects," Dr Parikh added. "They also underscore that atherosclerosis and cardiovascular disease are life-course diseases that have their roots early in life." Rosie Dodds, policy researcher for the National Childbirth Trust, said that the findings concurred with the World Health Organisation's own research into the long-term effects of being breast-fed as a child. "This study provides more evidence of the difference breast-feeding makes to blood pressure, obesity, diabetes and cholesterol levels," she said. "Women should be free to choose whether they breast-feed or not, but they should also have access to good information and support about their options. At the moment, that is what they are not getting in this country."


Genes and breastfeeding

This could be a rather pesky finding for the breastfeeding enthusiasts. Its conclusion is that breastfeeding is helpful in only some cases. And it does appear to be a very well-controlled study. The abstract is here. The authors do however rather overgeneralize the significance of their findings. The last sentence of their abstract is particularly silly. It is: "It also shows that genes may work via the environment to shape the IQ, helping to close the nature versus nurture debate". Nobody has ever questioned that IQ is a product of both genes and the environment -- but you do have to have the right genes to start with for an optimal result. The study would in fact appear to have identified one of the genes concerned

Children who are breast-fed go on to have slightly higher IQs than those who are not, but only if they carry a particular genetic variant, a British-based research team has found. The findings, from a group at King's College London, also provide new evidence that breast milk's nutritional content has a positive effect on infants' intellectual development, if only in those whose DNA lets them benefit.

While previous studies have linked higher IQ to being breast-fed as a baby, questions have been raised as to whether breast-feeding itself is responsible for the increase. Mothers who themselves have higher IQs are more likely to breast-feed in the first place, creating the possibility that genes that directly influence intelligence explain the link.

The new research, led by Professors Terrie Moffitt and Avshalom Caspi, makes it more likely that the nutritional content of breast milk has an active role, as it reveals a physiological mechanism that could account for the effect. The genetic variant carried by children whose IQ is improved when they are breast-fed is known to improve the way in which the body processes fatty acids that are critical to early brain development.

The findings suggest that a combination of the variant and breast-feeding increases the supply of these key acids to the brain, leading on average to greater intelligence. Without breast-feeding, or without the beneficial genetic variant, there is no effect. "Our findings support the idea that the nutritional content of breast milk accounts for the differences seen in human IQ," Professor Moffitt said. "But it's not a simple all-or-none connection: it depends to some extent on the genetic make-up of each infant. "There has been some criticism of earlier studies about breast-feeding and IQ, that they didn't control for socioeconomic status, or the mother's IQ or other factors. But our findings take an end-run around those arguments by showing the physiological mechanism that accounts for the difference."

The research, published in the journal Proceedings of the National Academy of Sciences, adds to the consensus that genes and the environment rarely work in isolation, but often combine to influence human development.

A separate study yesterday suggested that women who continued to drink alcohol during pregnancy would have badly behaved children. Brian D'Onofrio, of Indiana University, said that the children of mothers who drank less than once a week during pregnancy had virtually no behavioural problems, but women who drank on more than five days a week were storing up trouble for the future.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

And will "this generation of Western children be the first in history to lead shorter lives than their parents did"? This idea emanates from a much-cited editorial in a prominent medical journal that said so. Yet this editorial offered no statistical basis for its opinion -- an opinion that flies directly in the face of the available evidence.


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