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The Lancet just published a study that suggests "both low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did moderate intake." Link: https://www.thelancet.com/action/showPdf?pii=S2468-2667%2818%2930135-X
My inclination is to to say that observational studies like this are really not that useful, but if cutting out carbs is bad for life expectancy, I do want to know about it. Wondering what everyone else thinks?
Didn't read the study, but my first thought is whether this is correlation or causation. Perhaps celiacs eat few carbs and live shorter?
This is a general pattern for studies about health: if they say action X correlates with health problem Y, is it possible that the problem causes the action, rather than vice versa? Like, maybe a little alcohol is good for your health; but maybe it's not, only people who are "very sick, and therefore drink zero alcohol" drive down the statistics for teetotalers. Or, maybe too much sleep also hurts your health; but maybe there is a group of people suffering from some disease that makes them very tired or makes their sleep less refreshing, who drive down the statistics for people who sleep too long. (Even scarier hypothesis: maybe people who have a job are sleep-deprived as a rule, so getting enough sleep correlates with unemployment which correlates with disability, which makes enough sleep correlate with bad health. Like, if the research says 7 or 8 hours of sleep are optimal, as proved by correlations, maybe the optimal value is actually 9 hours but only the unemployed people can afford to sleep so long.)