This was on NBC Nightly News two nights ago:
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“The evidence would suggest that if one chooses nuts over other alternative foods, there is potentially a 20% improvement in mortality, which is quite striking.”
I’ll say. Does this mean you have a 20% better chance of dying (to follow my wife’s tendency to interpret things literally)? Or does it mean I have a 20% chance of living forever? Which is it? Either would be quite goddamned striking. I know that sound bite was taken out of context, but either way, it’s nonsensical – but it is what the public hears.
“The study found people who eat nuts tend to be thin and healthy.” Really? How interesting…
Just wanted to give you guys a glimpse of the bullshit machine in action. As recently put by James Thompson:
Most nutritional studies are observational, not experimental, and depend on questionnaires. There is always a nagging doubt as to whether every bacon sandwich and slice of chocolate cake will be faithfully reported, under the strain of recalling in vivid detail every lightly boiled cabbage and spoonful of cottage cheese.
Epidemiologists sometimes forget that people differ. Some are compliant boy scouts, some irresponsible spirits who don’t return questionnaires or follow instructions. Humans differ in intelligence and personality, but these considerations do not normally darken the door of diet epidemiologists. As far as they are concerned, people are what they eat, or become so after a decade of imprudent gluttony. Indeed, the meme “you are what you eat” seems to have had a great impact, despite being demonstrably false. Curious, the power of ideas, even stupid ones.
If any one wonders why we keep getting one pop diet fad advice after another, this is why. Medical science suffers from an over-reliance on observational studies. People trained to draw unwarranted conclusions from these studies however make up the backbone of the establishment, which is why we keep getting junk advice like this. As Thompson continues:
The other gripe among the cognoscenti? You read it here first. The sample sizes are too small, not followed long enough, and with high levels of sample attrition. Whoever you are, you cannot get round sampling theory. Samples of about 70,000 followed until death (with a proper link to death registers) will be required to identify even a few general patterns in diet which might account for a 5-10% increase in risk. If the studies are to mean anything, IQ, personality, sociological and occupational variables will have to enter the mix, and participants will probably have to be paid to stick to the course, and put up with random visits of inspectors looking in the fridge and the medicine cabinet. Count me out. So, although these correct and worthy researchers want controlled studies, they are not going to get them. Liberty will triumph over the food police.
These problems would in fact plague even randomized controlled trials, which I heavily advocate. In short, we continue to be utterly clueless which foods – if any – are useful to help ward off illness or extending life.
I will say this. Nuts are expensive. A decent sized can cost upwards of $5, which is one reason I don’t eat them anywhere as much I’d like, despite the fact that I love nuts (yes, I really do, all of you! :p). I’ll let you guys figure out the rest.
By the way, here’s the paper (abstract only, paywalled): “Association of Nut Consumption with Total and Cause-Specific Mortality”