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Monday, January 20, 2014

You Are Malnourished; Therefore, You Crave?

I consume food only while the sun is up.  This leads to natural twelve-hour fasts every day while the sun is down.  When I wake up, I usually have decaf coffee with Kerrygold butter, coconut oil, or both blended in with my Nutribullet.  It's foamy, fatty, and delicious!  While I'm preparing that, three or four slices of bacon are slowly frying to perfection.  I'll also eat about a half pound of greens and three or four eggs.  This is my breakfast nearly every morning. 

The hospital cafeteria food stinks, so I rarely eat throughout the day.  On occasion, however, I'll get a hankering for something around 10:00am.  This is especially true when I completed a particularly hard day of Krav Maga, Crossfit, climbing, or some combination of the three the day before.  The grumbling in my stomach doesn't discriminate when it comes to food.  I'm not craving a specific nutrient, I just want something in my face.  The coffee cart, gift shop, and cafeteria offer quick, easy calories in the form of candy, cookies, syrups for coffee, pastries, etc.  Thirty percent of the time, I cave, snarfing down an extra-large cookie or candy bar.  It tastes great, and I can eat it while I'm walking between patient rooms, but then I'll become hungry just an hour later.  On the other hand, I could go to the cafeteria and order two or three servings of their vegetable of the day, throw a pad or two of butter on top, squirt on some lemon juice, and I'm set until dinner time.  I'm often consuming less calories by choosing this path, yet I'm satisfied for longer.  As my Canadian friends might say: curious, eh?


Physiologic control of cravings

Man vs Food vs Diabetes
One of the most important things that you can do for yourself is to be cognizant of your nutrient intake. I'm not asking you to count carbs, protein, and fat.  This isn't about calories, nor is it about counting milligrams of vitamins or minerals. Simply stated, I believe that you are less likely to overeat if you eat nutritious food. 

My mother has always stated that her hunger persists perpetually throughout the day, regardless of how much she eats.  She can graze all day long on snacks around her office place, yet, without fail, she's hungry an hour later.  You've probably experienced something similar.  After a large meal of pasta, bread, and a few scoops of salad all of which is topped off with a big bowl or two of ice cream, you are aghast by the fact that you find yourself fumbling for munchies just a few hours later.  What gives?  You stuffed yourself Thanksgiving-style at dinner, but now you are hungrier than ever!

There are a variety of hormones that have been found to play some role in regulating appetite (see table).  We tend to explain the regulation of these hormones as a reflection of caloric deficiency, but, if this is the case, why is your hunger intractable to constant grazing? 

From: Austin J, Marks D. Hormonal Regulators of Appetite. Int J Pediatr Endocrinol. 2009

The nutrient deficiency hypothesis of hunger

It has been proposed that hunger is influenced by nourishment: the more nutritious a meal, the more satisfied you feel.  Put another way, cravings could be interpreted as malnourishment.  This isn't a new concept, as research efforts have been made to link glucose homeostasis to nutrient-sensing pathways in the hypothalamus; however, it is still unclear how exactly the brain or tissues detect these deficiencies.  

Overweight individuals tend to be deficient in various nutrients and vitamins, including selenium, iron, vitamins C/E, and vitamin D.  Indeed, a paper from 2009 started off with this in their introductory paragraph:

"The presence of nutritional deficiencies in overweight and obesity may seem paradoxical in light of excess caloric intake, but several micronutrient deficiencies appear to be higher in prevalence in overweight and obese adults and children. Causes are multi-factorial and include decreased consumption of fruits and vegetables, increased intake of high calorie, but nutritionally poor quality foods, as well as increased adiposity which may influence the storage and availability of some nutrients"  

A relevant question would be, "Are you nutrient deficient because you are overweight?  Or are you obese because you are consuming excess energy in response to nutrient deficiency?" Several interesting studies have been conducted to answer this question, but the data is inconclusive.  One study showed that "multivitamin and mineral supplementation during a weight-reducing program seems to have an appetite-related effect in women." [emphasis mine]  They asked women to rate their cravings throughout the weight loss program, and the multi-vitamin + multi-mineral supplement "had a beneficial effect on appetite-rating variables in women...even when change in body weight was taken into account, suggesting that an adequate intake in vitamins and minerals might influence satiety."   In other words, when we correct nutrient deficiencies, it seems to curb overeating.


Possible role of serotonin in linking cravings to nutrient-deficiency

Serotonin is a neurotransmitter that improves mood but reduces sexual desire, body temperature, and appetite.  Nutrient deficiency has also been linked to serotonin deficiency and thus poor appetite control.  If serotonin is deficient or unable to do its job (i.e. can't interact with receptors), your mood may turn downward but your appetite will be enhanced.  On the other hand, if serotonin is present in large quantities, you'll experience the opposite.  Similar to the influence of high insulin levels in the blood in the development of insulin resistance, chronically high serotonin levels can result in the down-regulation of serotonin receptors on your brain neurons, leading to a state that mimics deficiency.  That is: too little serotonin or not enough receptors will lead to deficiency in the action of serotonin.  

Psychiatrists often prescribe serotonin-selective re-uptake inhibitors (SSRIs), a class of drugs that prolongs the life of serotonin in the brain, to treat depression.  By enhancing the activity of serotonin, these drugs improve your mood but also decrease your appetite.  The side effect profile of these drugs includes weight loss in the beginning, but long-term therapy will eventually lead to weight gain.  This makes sense.  When you first start taking an SSRI, you experience high serotonin levels.  After all, this is the purpose of the drug!  Subjectively, you will experience improved mood, decreased appetite, and decreased sex drive (no comment on how this might secondarily kill your mood) due to high serotonin levels.  On the other hand, after you've been taking an SSRI for a year fews, you slowly become desensitized to serotonin due to the aforementioned down-regulation of receptors.  You experience a relative increase in appetite, and the drug will become less effective at positively influencing your mood.  Bingo.
S stands for Serotonin and Satiety

So what does this have to do with cravings?  As it turns out, correcting nutrient deficiencies - namely amino acids (e.g. tryptophan), vitamins (e.g. B6), and other nutrients - may be a viable non-pharmacological treatment for depression by optimizing serotonin levels.  Could this be the link between nutrient deficiency and cravings?  The truth is that I don't know; our understanding of these relationships is tenuous at best.  Because serotonin synthesis is also benefitted from exposure to sunlight, if there is a true link perhaps your office job is what's driving your hunger rather than nutrient deficiency after all.  Or maybe it's a combination of several factors producing your symptoms.  A lot more work needs to be done to further elucidate the role of nutrient deficiencies in craving control.  


Behaving Your Craving

The obvious problem with responding to cravings by munching is that convenience foods are often loaded with calories but otherwise relatively deficient in nutrition.  The fact that you reach for a bag of pretzels when you're hungry isn't proof that your body is deficient in sugar (or pretzels...though that would be awesome).  This is naive from both a physiological and evolutionary standpoint.  If you have extra pounds that you want to lose, your body is screaming "Fill me up!" for entirely the wrong reasons since there is plenty of fuel laying around.  

Furthermore, sugar does, in fact, trigger a release of serotonin from the brain, but this might only be as useful as pounding a diabetic's blood stream with insulin in order to chokehold their insulin-resistant tissues into responding.  After all, people who are depressed tend to eat more sugar (and gain weight as a result) because of the serotonin-sugar link, but an underlying problem plausibly still exists, and deriving happiness from Pixie Stix isn't a feasible solution.  In addition, let's not forget about your amygdalae, the structures in the brain that drive your impulsive snacking behavior.  The fact that you feel compelled to eat convenient junk foods is obviously more than just a sign of nutrient deficiency.

Yet, nutrient deficiency likely contributes at least in part to your perpetual cravings, even though the clinical evidence hasn't been sufficient to prove it just yet.  If this is the case, deficiency in X may be stimulating your cravings, and no matter how many calories you consume of a food that doesn't contain X, your cravings won't subside.  In fact, you could eat five times your regular caloric intake, but you'll remain deficient in X if all of these extra calories are deficient in X.  If X happens to be a precursor to serotonin production, then this is very likely the case.   Paul Jaminet describes this beautifully in Chapter 17 of his book, The Perfect Health Diet.  

Regardless of the source of your cravings, you know that proper nutrition is critical for optimal health.  Your bio-individual blueprint requires its own personalized proportion of vitamins, minerals, and macronutrients, so it's difficult to declare the specific proportions of ingredients to add into your body's milkshake in order to bring all the boys to the yard.  If you are eating a nutritious diet loaded with healthy saturated fats, sustainably-raised protein, and select starches, you're probably going to fare better than if you try to stave off cravings with the "empty calories" found in soda, pretzels, and candy.  

Try eating a truly balanced diet for 30 days, and reflect on how you feel.  Our basic dietary recommendations can be found here.  I'd bet that you'll start feeling better, sleeping better, and craving less.  




Nathan Riley is a 2014 MD candidate at Temple University School of Medicine.  He writes about food, movement, sleep, relationships, and stress in order to bridge the gap between his patients and evolutionary theory and clinical evidence. You call follow him on Twitter @BeyondtheMD.  He can be reached at nathan@sweatandbutter.com.  You can also connect with him on Google+. 



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