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In today’s edition of Dear Mark, I cover two topics near and dear to many of your hearts. First, I discuss the interaction between coffee intake and insulin. Does coffee stimulate its secretion? Does it impair insulin’s function, or our body’s reaction to it? Find out how you should approach coffee on a Primal Blueprint eating plan. Then, I explore the suitability of dietary fat in the post-workout meal. Does it belong? Should you be stocking skim milk, de-fatted chicken breast, non-fat yogurt, and cartons of egg whites for your post-workout meals? If you’ve just lifted something heavy, should you therefore shun the yolks and fear the fat for the rest of the day? Find out below.
Does coffee raise insulin levels? A lot of contradictory stuff out there. Hoping you could get to the bottom of it. Also, how does it affect GABA?
What makes coffee research so confusing is that a lot of it is actually caffeine research. You see, researchers love isolating whole food constituents to avoid confounding variables. It’s easier to get a definitive result about caffeine than it is to get one about coffee, because coffee contains huge and diverse levels of antioxidant compounds. If you don’t, and coffee has a health effect, how do you know if it’s the caffeine or something else in coffee causing the effect? That’s helpful, but most of us are drinking coffee — not popping caffeine pills. So, while caffeine is definitely one of the main active compounds in coffee, it’s not the only one. Adjust your interpretation of “coffee” research accordingly.
That said, both caffeine and coffee have been shown to exert negative effects on insulin sensitivity. Not on insulin itself, though. As standalone substances (without a meal to accompany them), neither caffeine nor coffee have an independent effect on insulin secretion.
But insulin sensitivity, the efficiency with which your body handles incoming glucose? Yeah. Caffeine tends to reduce it. It’s not necessarily a terrible thing, though, when you consider why this occurs. Caffeine increases adrenaline, which increases lipolysis — the liberation of fatty acids from body fat. The increased sense of energy you get from coffee is partly caused by the increased availability of energy in the form of free fatty acids. Of course, an increase in free fatty acids shooting around your body causes a subsequent — and necessary — drop in insulin sensitivity to allow you to actually burn the fat. It all makes perfect sense when you consider the entire picture, but it sounds pretty scary out of context.
Despite all the clinical trials showing that acute intakes of caffeine and coffee tend to reduce insulin sensitivity, the overwhelming majority of the observational literature finds that coffee is linked to lower body weight and protection from type 2 diabetes. Heck, heavy coffee drinking is even linked to protection against non-alcoholic fatty liver disease, an affliction characterized by insulin resistance. And although what I’ve said about correlation and causation in the past holds true in this case (even though it’s supporting something that we might like), the connection is undeniably interesting, especially when you consider that heavy coffee drinking is universally lauded as unhealthy and that habitual coffee drinkers are probably more likely to smoke, stay up late, and eat bad food. Perhaps there is a mechanism there (one suggestion in the NAFLD paper is the antioxidant content of coffee).
Part of it stems from the fact that habituation to a behavior affects the effects of that behavior. You know how once you’ve been drinking coffee for awhile, you don’t really get the “buzz” anymore? You still love (need) the stuff, but it’s not so much a stimulant as it is a normalizer. Well, the coffee buzz comes partially from adrenaline, the secretion of which drinking coffee promotes. Adrenaline is also a potent stimulator of lipolysis, the release of free fatty acids from adipose tissue. Since the liberated fatty acids are causing the temporary insulin resistance, and the fatty acids are liberated by adrenaline, and the adrenaline buzz is lessened with habitual coffee drinking, maybe the insulin resistance is similarly lessened when you’re a coffee fiend. Sounds sensible, right, but what does the research say?
Sure enough, when you give overweight, generally healthy habitual coffee drinkers five more cups a day and measure their “biological risk factors for type 2 diabetes,” things look a little different. Their insulin sensitivity not only stays the same, but their risk factors actually improve. Markers of both liver function and adipose tissue function were improved after upping their coffee intake.