Articles to 2014-10-19

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First the link to this week’s complete list as HTML and as PDF.

Successful teachers have always scattered witty or engaging anecdotes throughout their more serious stuff. Gruber et al. now show why this is so effective.

Currently the press is full about stretching before sport being not only not beneficial but downright harmful. None of them bother with citing references of course, but after digging them out we find, not surprisingly, there’s nothing in it. As Feynman said: Never believe the experts, always read the sources yourself.

Wood et al.’s result is not particularly interesting of itself, but it’s one more example why the search for the genetic base of more relevant traits probably is useless too. With thousands of genes behind one trait thew numbers alone dictate that every gene has to influence a number of attributes equally. This may help complex adaptation in nature but more or less destroys any hope for genetic engineering.

Do artificial sweeteners induce hunger and thus indirectly lead to more, not less calorific intake? The meta-study by Bellisle & Drewnowski denies it. The studies therein rely on subjective hunger reporting and weight gain in humans. The latter is an extremely coarse measure. Short term weight fluctuations are dominated by water and other confounders to such a degree, that anything less than a kilogram is probably meaningless. These studies have to be either extremely short term or plagued by a huge number of uncontrollable confounders, so none of them can be expected to yield a meaningful result from the outset. As far as I can tell from my admittedly short search, there has been no attempt to measure a possible insulin reaction to sweet taste directly.
    The result on cell cultures by Malaisse et al. is very surprising, as it completely eliminates the proposed mechanism through taste and the central nervous system. Pancreas cells reacting directly to at least some sweeteners make the connection even stronger than previously proposed. I could find nothing to fault that result.
    Lastly Swithers & Davidson attacked the question in an exceptionally well planned and highly controlled experiment and were able definitely to confirm the proposed effect through several different measures, even if their figures 7 and 8 suggest that habitual users of sweeteners may be able to compensate to a degree. (Which means that real sugar will satiate them less and be worked off less than in those unaccustomed to sweeteners. Those using both may end up twice hit.) This study should settle the debate conclusively.
    In all while one might still argue that the proposed mechanism is not proven until there are direct insulin measurements in humans, it is certainly clear that the claim for it to have been undeniably refuted, based mainly on Bellisle & Drewnowski, cannot stand.

In a new publication of this week Feehley and Suez demonstrate another direct mechanism by which sweeteners promote and do not ameliorate obesity.

Four years ago Bodinham et al. and Johnston et al. were able to suppress the hunger spike after consumption of white flour through the addition, not just substitution, of what they called Resistant starch. A surprising as yet unpublished new result announced by the BBC and the Independant is that just this kind of starch is generated in pasta simply by cooling and reheating.

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