Dear Mark: Carb Concessions, Nitric Oxide, and Chronic Cardio

“Winter is coming.” (Albeit, a Malibu winter, which is closer to a somewhat mild spring in other parts of the country, so I can’t really complain; I just wanted to use that quote contextually.) Yep, I’ve been catching up on “Game of Thrones.” Dang fine show, but now the long slow agonizing wait for the second season commences. Anyone else watch?

Anyway, it’s Monday, which means it’s time for another round of Dear Mark questions and answers. I field one from an ecologist soon to be working out of Nicaragua and worried about making dietary concessions and balancing Primal eating with cultural faux pas. Next, I discuss nitric oxide supplementation, and whether there’s a better way than taking it direct. Finally, I explain how one determines the chronic cardio-ness of an activity.

Let’s go.

Hi Mark

I’m in the process of switching over to a Primal [Blueprint] diet, and I have a question that might be good for your “Ask Mark” posts.

My upcoming challenge is a 3-week trip to Nicaragua, where I do a lot of field work (I am an ecologist). While they have THE BEST grass-fed beef there (I’m drooling just thinking about it), it is also going to freak people out that I will be turning down rice and beans (fried in trans-fat laden vegetable shortening, no less).

I’ll probably have to make some concessions — when a campesino offers you a plate of hard-won beans grown by the family, it doesn’t sit well to turn your nose up at it and talk about carbs! But I’m also wondering if some of the other “carby” choices might be acceptable in a pinch. Specifically, plantains (eaten both in green and ripe forms, the latter usually fried; green plantains may be boiled or fried) and yucca (usually boiled) can commonly turn up on the menu, and asking for extra boiled green bananas might make up for the faux pas of turning down the rice.

Another thing likely to turn up at every meal — corn tortillas! You’ve discussed the detrimental effects of straight-up corn in your blog, but the tortillas are made from corn after it has undergone a process of soaking in an alkaline solution (known as nixtamalization). This process is widely known to improve the nutrient profile of corn, but I’m wondering if it similarly removes some of corn’s “anti-nutrients”?



First off, you’re right to recognize that “Primal purity” has to go out the door in certain instances. At a buffet dinner for work? Sure, go ahead and politely pass. Wax poetic about why you aren’t eating something. Get into it with a vegetarian. But when a host family offers the clothes off their backs or the beans from their pantry, you generally accept. Definitely make those concessions when they’re necessary – provided you don’t have serious digestive issues with particular foods that you know will cause problems. And no one says you have to finish everything that’s on your plate. Remember – 80/20.

Yucca and plantains are good choices. Obviously, go for the boiled ones when you can, especially if they’re using “trans-fat laden vegetable shortening” to fry them, and rest assured that these are “safe starches.” In fact, yucca root (also known as cassava), is the third most-eaten source of starch in the entire world. It does contain high levels of cyanide, but proper processing totally removes all traces of the toxin. And remember, rice isn’t all that bad, either.

Nixtamalized corn is also a fair concession. Corn can come with mycotoxins, a category of toxic molds that often grows on cereal grains or legumes that have been stored improperly. In years past, I’ve written about peanuts and afltatoxin, one of the more notorious mycotoxins dangerous to humans as well as animals. Luckily, nixtamalization destroys the bulk of mycotoxins present in the corn before processing.

I’ve searched but haven’t found anything regarding your feelings of taking nitric oxide as a supplement prior to working out. CNN is pushing it for older guys (I’m 45) as similar in effect to steroids but healthy. Thoughts? Thanks for everything. I hope to post a before and after story soon.


Much has been made of the ability of nitric oxide to increase performance and stamina, especially in high-intensity activities. It’s legit. In one recent study, nitric oxide in the body reduced the oxygen cost of exercise, improved stamina, and increased performance. Nitric oxide literally widens blood vessels and arteries, thus increasing blood flow to tissues (and the amount of nutrients that blood carries to those tissues). It even reduces blood pressure, and an earlier study had extremely similar results in cyclists. So it appears to work.

But there’s a catch: neither study used nitric oxide supplements. Instead, they used nitric oxide precursors, or substances that the body uses to produce its own endogenous nitric oxide. The earlier study used beetroot juice, a good source of nitrate. Nitrate is converted into nitric oxide in the body. In the second study, researchers increased nitric oxide by administering L-arginine, an amino acid precursor to endogenous nitric oxide production. There is very little evidence that direct nitric oxide supplementation increases exercise performance, so I’d save your money and eat beets or take arginine supplements. Nitric oxide may work directly, but the precursors are proven to work and are likely far less expensive. I’m reminded of the glutathione situation, wherein supplementing with precursors is far more effective than taking the thing itself.

If you do a before and after story, I’d be really interested in hearing whether trying to increase your own nitric oxide production helped your performance.

Oh, and I’ll have you know that 45 ain’t old!

Dear Mark,

I think you’ve addressed this in the past but maybe not directly. I’m wondering just what you would consider “chronic cardio”. I know the drudgery of the treadmill or the elliptical. But I’m wondering about this… when I’m able, and sometimes that’s every day for weeks or months at a time, I ride my bike to work. It’s a healthy ride, 15 hilly miles each way. Takes about an hour each way. So that’s chronic, right? Two hours a day every day. But it’s biking and it’s hilly, so there can be lots of coasting, periodic hard ascents, and a fair amount of standing a stop-lights. Is this chronic cardio?


Falls Church, VA

My criteria for characterizing an activity as “chronic cardio” is more qualitative than quantitative. While some figures can be used as rough indicators (for the average Joe, obligatorily hitting the treadmill to “burn 500 calories” every day of the week usually constitutes chronic cardio), I’m more interested in how an individual personally responds to and regards a particular “cardio” activity than the distance and frequency traveled. For me, running anything longer than a few miles is “chronic,” because it stops being a pleasant, light run where I’m enjoying the sights, sounds, and smells and quickly becomes a grim battle against time and whoever else is running nearby. I get sucked into the competitive tunnel vision. With each stride, I grimace and descend deeper into the abyss. But that’s me.

You call your ride “healthy” and generally seem to have a good relationship with it. It’s not a race; it’s how you get from point A to point B. It’s not a straight shot, as you say. There are dips and climbs and coastings and chances to rest. You mention drudgery, but indicate that this bike ride is not that. This is a good thing. Now, if you’re dreading the bike ride every morning, if you’re sluggish to get up because your joints are aching, if your other workouts are suffering, or if you’re eating gallons of ice cream every night to fuel your activities… maybe the bike ride is a little excessive. But I don’t get that from you. Do you enjoy the ride? Do you feel stronger and more capable, rather than weaker and run down, as a result of riding? If you can answer yes to both, I’d say it isn’t chronic. Don’t sweat it.

Let me be clear, though. To any endurance junkies out there, no matter how much you love logging scores of miles each week, it’s still chronic cardio. I’m not saying you shouldn’t do it. Follow your passion. But just be aware that it isn’t the healthiest thing you could be doing, in my most humble opinion.

That’s it for today. In the comment section, go ahead with any followup questions and I’ll try to get to them. Thanks for reading!

TAGS:  dear mark

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending more than three decades educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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