For today’s edition of Dear Mark , we’ve got a three-parter that’s really closer to a five-parter. First are a couple of questions from Joe, who first wonders about the hormetic benefits of acute sleep deprivation (are there any?) and then asks how he can beat a sweet tooth he suspects is brought on by lack of exercise. The second pair of questions concern CrossFit (is it an example of Chronic Cardio and should I be recommending it?) and breadfruit (does it have a place on the Primal eating plan?). And finally, Andy asks for the origin of the popular “gut is 80% of our immune system” statement.
Thanks for all you do. Your work provides a wealth of knowledge (accurate and not self-seeking), and I consider myself blessed to have found MDA.
Question 1: I have read various articles of yours in which you discuss hormesis, and I agree with the idea that an occasional stressor or toxin improves the body’s biological functioning. Obviously, there are exceptions here. Exposure to poisons such as cyanide do not bode well for those exposed. But I have also read your articles on sleep. While I couldn’t agree more that regular, quality sleep is vital to our ability to thrive, I am curious to know if there has been any research on a hormetic effect of the occasional sleepless night (or the occasional night with poor quality sleep). It seems logical to me that this kind of occasional stressor would not necessarily be detrimental, but perhaps beneficial. I also wonder about how Grok would have slept. While he was probably free of all our modern distractions and artificial light, I imagine he would need to wake up to protect his family from predators, for example. I would like to get your thoughts on this.
Question 2: I have been living Primally for over two years now, and while I feel much better than I did before I discovered the Primal Lifestyle I have never been able to kick my craving of sweets. Generally I will satisfy my cravings with some quality dark chocolate, some raw, local honey here and there, or the occasional Primal/Paleo dessert, but I believe I may just have a “sweet tooth” because I crave dessert regularly. Is there something I can/should do to cut down these cravings? Increasing my good quality fat intake does not make much of a difference for me. I’m wondering if perhaps it’s exercise. With two young children and two jobs, I have trouble finding time to exercise the way I’d like to exercise. Usually the maximum exercise I get in a day is playing with my two year old daughter, which includes lifting and carrying her, and tossing her into the air and catching her. I would appreciate your advice.
Thanks again, Mark. I hope you have a great day.
Hey, Joe. Great questions. First, sleep deprivation as a hormetic stressor? That’s really interesting and there is some evidence for it.
Using a mouse model of cardiac arrest, researchers showed  that acute sleep deprivation can reduce the inflammatory response and stave off the death of heart cells. Puzzled (since they assumed sleep deprivation was always detrimental), they dosed mice with lipopolysaccharide to test whether the effect held for general inflammation , too. It did. Acute sleep deprivation lowered expression of inflammatory factors and increased release of an anti-inflammatory cytokine.
In patients with depression (which is often characterized by wanting to sleep all the time), sleep deprivation has been used improve symptoms . A small percentage (2-7%) of patients worsen with sleep deprivation, but the vast majority see improvements. Some patients even enjoy total remission. And though the improvements usually diminish a bit after recovery sleep, they generally do not disappear, with some patients enjoying the benefits for weeks. The key here seems to be breaking the cycle of excessive sleep. Not daily, of course; chronic sleep deprivation will only make things worse and is actually a risk factor for developing depression  in the first place. But the occasional night of “bad” sleep could improve your depressive symptoms, and improve them quickly.
If any of you are interested in trying acute sleep deprivation for depression, check out this 2011 article  where the authors lay out a fairly comprehensive protocol for clinicians.
(Any people with depression out there notice a similar effect of sleep deprivation on the severity of their symptoms? I’d be interested to hear.)
Second question: sweet cravings , and what could be causing them.
Your schedule sounds really demanding, and I suspect the stress of it all is manifesting as a sweet tooth. You’re whizzing from job to parenting to job to parenting to (probably broken and insufficient) sleep to cramming some food down your and your kids’ mouths to job… and so on. That’s a lot of responsibility and stress  without a lot of breaks.
First, check out my general recommendations for stress reduction . Do what you can there. As for exercise…
Exercise  definitely can reduce stress. Although it’s a “stressor ” in its own right, I’ve found that exercise kills stress – or at least provides something for me to focus on that isn’t related to whatever is stressing me out. If I’m feeling overwhelmed with work or thinking too heavily about a project, I’ll often take a break to go lift weights, run a few sprints , or take a long walk. When I’m physically active, it’s difficult for my mind to be anywhere but the moment – the thing I’m doing. The problem is still there when I return, but it isn’t so stressful anymore and I have a slightly different, clearer perspective that lets me tackle the problem without the hangups. Taking that break from endless thinking about thinking about the problem really, really helps.
Since your schedule is pretty full and you have two small kids, you’ll have to get creative in order to exercise. Here are some ideas:
Take your kids to the playground and/or park every day, even if just for half an hour. Join them on the jungle gym for pullups  and rows and pushups . Swing arm over arm along the monkey bars. Play tag; they run, you crawl . Practice somersaults, cartwheels, handstands, jumps, and tumbles . Balance on handrails, park benches, equipment. If you feel you have to choose between dinner time and play, do an early evening picnic at the park! Play, then eat. There’s no reason you have to eat inside. Same goes for homework or anything else that can technically be done anywhere.
Keep up and progress with the toddler lifting. Lifting and throwing a two year old human is a pretty good workout, but you can do much more than a few throws  and lifts. Try walking lunges while carrying the kid. Try overhead presses. Try single leg deadlifts. Try toddler kettlebell swings. For heavier sets, use the older kid; the squirming and protesting will only increase the difficulty and benefits.
Check out Darryl Edwards’ Fitness Explorer  site. He’s one of the most innovative thinkers in the fitness community because he focuses entirely on play – on having fun, laughing your a** off, and getting a great workout in the process. He even did a guest post on MDA  last year that lays out his philosophy and gives you a few ideas to get started playing. There’s a reason he’s a mainstay at PrimalCon .
Try to go for a short walk every day with your kids, especially the little one. Maybe after dinner. Maybe just around the block. Maybe just ten or fifteen minutes, if that’s all you can spare. It’s a great way for you to get some regular activity (and lower blood glucose after a meal , if you’re into that sort of thing) and it’ll help instill walking as a normal, everyday habit in your kids.
Go for a long hike with the kids on your day off. Carrying a two year old up a steep incline for a couple miles is a killer workout. Plus, getting out into nature  on a regular basis will melt away the stress .
Sprint. A few short, brutal hill sprints take 10, 15 minutes and then you’re done for the week. You might also pick up a stationary bike so you can sprint while watching the kids. Look for a Schwinn Airdyne; you can often find them used on Craigslist.
Oh, and don’t sweat it if you have a bit of a dark chocolate  habit. I have the same “problem.” Keep up the good work. It sounds like your kids are lucky to have you.
Your blog has been a big and positive influence on me. In addition to overall dietary and exercise advise, I now use resistant starch, and it’s been of huge benefit. Thank you!
Question. I do Pilates, fitness classes like springboard that get me on my feet, and lift at home. I have not done much “chronic cardio” over the past 20 years, and I’m glad I haven’t. Those workout classes I do aren’t super intense cardio. But I’m curious why you seem as positive as you do about CrossFit, which seems as though it can be *abusively* intense cardio, to the point where people are throwing up and liquifying their muscle tissue. There are lots of great Primal things about CrossFit, but this would seem to be a big check mark against it.
Blog post idea. I tried breadfruit for the first time recently in a curry I made, and it was amazing! Could this possibly be a nice addition to the Primal diet? It is incredibly dense and satisfying in a way no other carb I’ve tried is–much more so than potatoes or sweet potatoes. I thought taking a look into it could be a nice post. And do try it if you haven’t yet!
All my best,
Thanks, Matt. Glad to hear resistant starch is helping!
I always make the point that CrossFit is a highly demanding lifestyle choice that may be difficult with very low-carb eating. Just about every week I’ll hear from a CrossFit enthusiast who’s hitting a wall. Last week’s Dear Mark , for example, featured a question from a woman who just couldn’t shake the carb cravings. She was doing CrossFit five days a week and wanted to become a fat-burning beast ; I told her she’d probably have to cut back on the CF WODs and include far more easy, low level movement and pure strength training.
I think the 3 days on, 1 day off schedule is excessive for most people trying to juggle a job, a social life, parenting/other responsibilities, other fitness pursuits. Unless you’re a full time CrossFit athlete, or CrossFit coach, it’s probably not advisable. But for many people, their CrossFit box is their social circle and their playtime , and that’s awesome. They love what they’re doing while getting a great workout with good friends. There’s not much better than that.
As to your second question, breadfruit’s great. It’s not a regular thing for me, since it’s a tropical food and not widely available, but whenever I get out to Kauai I make it a point to have some. The cool thing about breadfruit is that it’s essentially three or four foods in one.
Immature breadfruit is like a vegetable. Some compare it to artichoke hearts. You can pickle , boil, or steam it.
More mature breadfruit is sweet and starchy. Treat it like a sweet potato .
Fully ripe breadfruit can be eaten raw. It’s sticky and sweet.
I can see breadfruit working very well at any stage in a curry .
I hear the statement that “80% of the immune system is in the gut” many times in the paleosphere. I have tried to find what this actually, specifically means, and how it is calculated, but can’t seem to locate anything concrete. Could you shed some light on this?
This paper lays it out pretty succinctly: 70-80% of your body’s immune cells are found in the gut tissues . But that doesn’t really tell us anything concrete about the role of the gut in the immune system. Let’s look a little more closely:
The gut is a physical barrier  to invading pathogens and errant, potentially allergenic particles. The first line of immunity is always a physical barrier. Skin’s another example of a physical barrier.
The gut is also a dynamic barrier. Intestinal tight junctions  lining the gut act as doormen of the bloodstream, regulating the passage of nutrients into circulation and keeping allergenic, toxic, or pathogenic particles and microbes out.
The gut produces the majority of our antibodies . Our immune system uses antibodies (like IgA) to identify, target, and destroy foreign invaders.
The gut induces vomiting and/or diarrhea. If the specialized receptors perceive a poison or toxic load, vomiting and/or diarrhea may be induced and powerful contractions of the gut musculature engaged to rid the body of the dangerous contents.
And then you have the gut bacteria, those important players in immunity  residing on and in the gut. You can’t count them out, even if they’re not “you.”
Gut bacteria protect against pathogen colonization by taking up space along the intestinal wall. That’s why antibiotics can ultimately damage our immune systems; they often kill everything  (not just the pathogens responsible for the current infection) and clear a path for pathogenic bacterial colonization once the antibiotic course ends.
Gut bacteria are required for optimal development of the innate immune system. White blood cells – neutrophils, macrophages, and monocytes – are the backbone of the innate immune response, and animals born without gut bacteria grow up with far fewer of them .
Gut bacteria can determine food intolerances and allergies. Some gut bacteria induce inflammatory responses  that prevent allergens from accessing our blood and provoking further response. Other bacteria respond to prebiotics  like inulin  and resistant starch  by increasing butyrate production, which reduces intestinal permeability and allergy/food intolerance .
Now, that wasn’t close to being comprehensive. It would take an entire book to lay out all the immune responsibilities of our guts and their inhabitants, but I think you get the idea.
Thanks for reading, all! Take care and have a great rest of the week. As always, if you have any tips for Joe (and comments/responses for Andy or Matt), feel free to contribute to the comment board!