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Dear Mark: Sprints and Blood Sugar, Resistant Starch as Carbs, PUFA in Coconut Oil, Cycling as Chronic Cardio, and Morning Sickness

For today’s edition of Dear Mark [7], I cover four questions and my wife Carrie covers one. First, I discuss the effects of sprinting on blood sugar in the short term and long term. Next is whether or not one counts resistant starch [8] as a carb in their daily allotment. Third, I identify the actual proportion of omega-6 polyunsaturated fatty acids [9] found in coconut oil. Finally, I give my take on cycling as a gentler mode of chronic cardio [10] relative to running. Carrie wraps things up with a short review of the evolutionary reasons for morning sickness.

Let’s go:

Dear Mark

I see a lot of talk on your site about sprints and how great they are. My question is, what is their effect on blood sugar immediately after a session? As a recovering T2 diabetic living primally for about a year, I hadn’t had a large spike in blood sugar in weeks…until I tried some sprints (jump rope to be precise). I was back to normal about 1/2 hr later.

What’s a normal immediate blood glucose response? Are there any health detriments to blood sugar spikes due to intense exercise?


That’s totally normal, Clark. Sprinting [11] is a particularly glucose-intensive activity. It burns right through muscle glycogen [12]. Sensing this, the liver releases glucose to provide additional fuel for the body; in healthy people, type 2 diabetics, and type 1 diabetics alike, blood glucose spikes after most any exercise, but especially after sprinting [13]. It’s a feature, not a flaw.

The good news is that over the long haul, sprinting leads to improved glucose control. Heck, a type 2 diabetic doesn’t even need to wait more than day to start seeing massive improvements in his glucoregulation. A recent review [14] looked at the blood glucose responses of diabetics (type 1 and type 2) to “brief high intensity exercise,” as which sprinting definitely qualifies, finding that although glucose was elevated immediately post workout, blood glucose control is improved for one to three days following a sprint session.

Keep sprinting.

Hi there, do the carbs in resistant starch count as part of my daily carb intake. In other words if I am trying to stay at 90g of carbs a day and I am taking in 40g of carbs from the resistant starch, does that mean I have 50g left or are those carbs in a different category because they are processed differently?



No, they don’t really count. You’ve still got 90 grams left.

Resistant starch is resistant to digestion by the host organism (that’s you), acting more like prebiotic fiber [15] (food for your gut flora) than anything else. More and more, we’re beginning to understand the necessity of feeding our gut flora [16], which don’t just impact our digestion, but also our immunity [17] and cognition.

The cool part about resistant starch in relation to digestible starch is that its fermentation yields butyric acid, a short chain fat that actively improves insulin sensitivity and blood glucose control [18]. In other words, it helps you become more tolerant of the carbs you can digest.

Unless you’re heating up your resistant starch past 140 ºF, which would turn it into fully digestible regular old starch, resistant starch doesn’t convert en masse into glucose in the body.

I have a tablespoon of unrefined virgin coconut oil in my tea every morning, because of its health benefits. I was told recently that coconut oil is pure omega-6. Now I’m a little confused, should I be limiting my coconut oil intake like I do nuts or is there something about it’s structure that makes it different?Would you please clarify.



You’ve got a saboteur in your midst feeding you bad info. Coconut oil [19] is almost entirely saturated fat [20] with negligible levels of omega-6. Here’s the breakdown:

91% of the fat is saturated, mostly medium chain triglycerides [21] (fats like lauric acid, caprylic acid, capric acid, and caproic acid which boost ketone production and increase metabolism).

6% of the fat is monounsaturated (the same kind found in olive oil [22] and macadamia nuts [23]).

A lowly 3% of the fat is polyunsaturated [9] (omega-6).

You’re fine. Keep enjoying that coconut oil!

Have you done any more research into specific cardio versus just cardio in general?

In other words, respectfully, I question a little that cycling shouldn’t be separated from the “bad, too much cardio” group. Especially considering that with downhills, stopping at red lights/stop lights and the very social, stop and regroup aspect of it (well, for us amateur riders anyway) – couldn’t it be considered along the lines of sprinting and recovery? I know that on some rides, even centuries, I don’t pedal with full power the whole time, often just coast, and my heart rate goes way down often when I’m just spinning lightly and enjoying the views. Cycling is more a workout for the soul, as far as I’m concerned, and I’m just so torn on thinking that even on long rides (endurance rides) I’m doing myself any harm. It’s the weekend after weekend of long rides that I believe are where one could potentially run (ride) into trouble.

It’s just, I don’t know – given that it isn’t hard on the knees or joints (I ride a triple gear proudly to save my knees!), isn’t hard on the back (if you use your abs to hold your posture correctly!) and is just so social and enjoyable, wouldn’t cycling be considered primal in most ways?


Most research confirms that running is the riskiest of all the non-contact sports [24]. Triathlons afford us a direct comparison between running and cycling injury statistics in the same population. There’s some variance, but the running portion is usually linked to more injuries, as you might expect:

The main reason I stopped competing in marathons and switched over to triathlons is because it let me keep up my admittedly insane training and competing load without continuing the destructive trajectory of my joints and overall health. Of course, it didn’t last for long, but I did get a brief lull in degeneration by switching from all running to some running, some cycling, and some swimming.

Cycling is lower impact, but not “no-impact” when compared to running. Overuse injuries do occur, and force does act upon the joint when cycling. One study [29] compared the compressive forces acting on the knee cartilage when running and cycling by measuring the degree of cartilage deformation. Running created greater forces, deforming knee cartilage by 5%. Cycling wasn’t far behind, with 4.5% deformation. These deformations were transient and normal, but you can imagine how they might add up over the course of a session (or sessions). Any misalignment of your tissues – due to, perhaps, fatigue, overtraining [30], or tight surrounding musculature – will increase or at least concentrate the deformation.

Of course, running form is less linear than cycling form and that makes the runner more susceptible to overuse injuries. When you get tired on a run, your legs start to flare out to the side and your form gets sloppy. When you’re cycling, your form is more “locked in” by the pedals, even if you’re tired. This is probably why cycling is more forgiving to the joints.
Leaving joint issues aside, chronic cardio refers more to the long term effects of repeated medium-to-intense work that causes the heart to overreach and in many cases the heart wall to thicken. A-fib is a minor epidemic now among lifelong CCers [31].

It is possible to embark on a running program, a cycling program or a triathlon training program that steers you away from CC territory (cross-training, specific weight training, intervals, very slow paced running or riding and, yes, the occasional long, hard slog).

I have never said someone shouldn’t go out for a weekly long ride or run – even a hard one. Or even a few times a week if you’re fit and enjoy that – and can recover fully in between. I am just opposed to the day-in, day-out medium-to-hard effort that doesn’t really improve fitness, but just causes the heart to beat metronomically (not a good thing over a long effort) and to never fully recover. Endorphin addiction (the runner’s high) is not necessarily a good thing.

If cycling is improving your life, getting you out into nature [32], letting you hang out with your pals, then I’d say it’s worth doing. Just be wary of that threshold [33] where it starts taking away from your life, where you stop noticing the scenery or appreciating the nature, where you start neglecting your friends and family because you’re too sore or sleepy to do anything. It sounds like you know what you’re doing and you’re watching out for the warning signs.

Now, let’s hear from Carrie…

I have read in numerous places that “morning sickness”, as we Westerners know it, simply is non-existent in hunter-gatherer and primitive cultures…in fact they have no idea what such a term even means. These women enjoy easy, robust pregnancy’s with very few issues, and it is my understanding from anthropologists research, that stress is the true culprit that triggers morning sickness for us women living in modern societies. The levels of stress are far fewer, and of a different nature amongst primitive cultures then for us Westerner’s.

So, I am hoping that either you or Carrie can provide some insight on this truly miserable phenomena from an historical/anthropological viewpoint. An exploration into what it means to be preggo, and Primal/Paleo, would be a welcome subject to tackle here on MDA!

Thanks so much!!


Actually, morning sickness is fairly universal among pregnant women, regardless of culture, ethnicity, or diet. About 70% (give or take) of women experience food aversions and nausea during pregnancy [34], usually the first trimester, and modern research has generally coalesced around the “morning sickness as prophylactic” theory. Even if you’re a pastoral, rural Tanzanian woman [35] eating a whole foods diet, you will probably experience morning sickness when you get pregnant. Food aversions are there to keep potentially toxic or harmful foods or substances out of your body and away from the growing baby. It’s not a perfect system by any means, rather a blunt tool that removes large swathes of food that might actually be harmless or helpful but “fit the profile.”

For instance, wild plants are higher in polyphenols (or phytonutrients) than domesticated plants. Maybe too high, and that’s why we bred them out. In fact, phytonutrients can become phytotoxins at high enough concentrations. Mark has written about this before [36], but many of the benefits of phytonutrients come from our defensive reaction to them. We want the right amount, not too many, not too little. Then there are the outright toxins found in some wild plants. The end result is that domesticated plants get included in the aversions because our ancient bodies don’t really know the difference, even though they’re probably good for pregnant women.

Some phytonutrients reduce iron absorption. Others, like the ones found in cruciferous vegetables, can inhibit thyroid function when eaten in large amounts especially with concomitant low iodine intake [37]. Wild cruciferous vegetables have even more of these substances [38]. Both thyroid hormone and iron are essential for development of the fetus, so it makes sense that we would evolve built-in mechanisms to prevent overconsumption during pregnancy. Studies have also found connections between high consumption of polyphenols in late pregnancy and negative changes in fetal blood pressure dynamics [39]. A very recent trial even found that polyphenol restriction in the last trimester improved those flow dynamics [40]. Also, many herbal teas are contraindicated during pregnancy due to undesired health effects, and a widespread revulsion against bitter plants would have the same protective effect.

That’s also why pregnant women are more likely to remember people’s faces after just a single introduction [41], more sensitive to health cues, and more suspicious of “out-group” members – these are all protective measures to keep bad stuff (sick people, dangerous people, certain foods, toxins) away from the baby. I personally find it incredibly fascinating!

But you still need to eat, so what can you do in this case?

Hope that helps!

Thanks for reading, everyone.