Archive for June, 2012

Last week I gave a talk on evolutionary medicine to a group of ~50 medical students at my school. I really enjoy public speaking and I love talking about evolutionary medicine, so I had a blast (and the talk seemed to be well received).  I won’t try and recount exactly what I said in my talk, but as people seem to be interested in what I had to say I’ll try and provide a general idea of how the talk flowed, sharing the things that I think medical students should keep in the back of their mind as they go through their medical training.

I started with an introduction to evolutionary medicine…

An image from a 2010 Nature article on Evolutionary Medicine. (Particularly fun as Darwin did start to train as a physician at one point!) 

The term “Evolutionary Medicine” is rather broad, and can mean anything from how and why our enzymes work a specific way to why we respond to our modern environment (or a medicine, stress, or toxin) the way we do.  It stresses (to me at least) the fact that natural selection is everywhere, and we would do well to remember this (in medicine, business, policy, and life!). The term “Evolutionary Medicine” is sometimes used interchangeably with “Darwinian Medicine”, and is often mentioned during the discussion of “Ancestral Health”. These are all terms I hope that we will hear more of as medical education continues to evolve (selection pressure is everywhere, right?)

Speaking of med schools- I just read that the first lecture new med students get at UCSD is a lecture on evolutionary medicine [1]. Very cool! I like the idea of introducing the subject to med students before the onset of clinical training, as it offers a paradigm in which to think about health and disease, instead of trying to learn everything from a purely mechanistic perspective.

As med students, we are already familiar with some selective pressures that alter human health. Microbial resistance to antibiotics, sickle cell anemia, and lactose intolerance (though perhaps more accurately, “lactase persistence”) are all things we learn about, and are probably (hopefully?) taught with an emphasis on the selection pressures that brought these things to prevalence. These three examples, however, are just the tip of the iceberg.

We can use evolutionary medicine (and indeed I think we should) at all levels of human health and disease, but I think that an excellent starting point for this discussion is to take a step back and look at the bigger picture of “what it is to be human”.

So what is “being human”?

I find the easiest way to look at this question is to ask “how does a human live ‘in the wild’”. I’m not talking about a weekend camping trip, or even a half-year adventure through the rugged arctic, but rather, what can we glean from archeological evidence, our closest hominid relatives, and native peoples about how humans evolved? Alas, many native cultures are converting (or already have converted) to a more modern lifestyle, but there is a lot that we can learn from the lifestyle of people such as the Australian Aboriginals, the New Zealand Maori, Native Americans, Kitavans, Inuit, Maasai, and others.  Even though much cultural identity has been lost in recent generations, memories and documentation exist that we can use to better understand traditionally living humans.

I should say, at the outset, that this is not a plea to return to a traditional lifestyle (nor do I think people living in traditional cultures should be barred the opportunity to adopt aspects of our modern life). This isn’t about “going back” or recreating a specific lifestyle. Instead, this is about understanding our past so we can thrive in the present (and beyond).

Perhaps first and foremost (and indeed, my starting point into evolutionary wellness (there I go using yet another term)) is the food that humans thrive on. It is increasingly evident that there is not one “perfect human diet” that we evolved to thrive on. Rather, there are a number of foods that nourish and sustain our body in a healthy way. Humans evolved eating (and indeed some of these things truly ‘made us human’) meat, seafood, eggs, vegetables, fruits, nuts, and tubers.

What about grains and dairy? This is inevitably the cry we will hear from patients, friends, family, and hospital nutritionists! To hear these people talk is to think that humans cannot exist without these two staves of life. As much as people think of these things as staples of the human diet, the reality is that they were most likely not consumed in any real quantity until the agricultural revolution, a mere 10,000 years ago (not much time when you consider the span of human evolution). While it is true some people do well on these foods (and indeed, lactase persistence gave some a significant reproductive advantage at some point in the last 10,000 years), many people do not. Even those that seem to tolerate these things well are often surprised by the benefits they experience when these things are eliminated from the diet. Not everyone does poorly on these foods, but it definitely seems that many have not evolved to thrive on them.

Perhaps more important than thinking about what humans evolved to eat is thinking about what is truly novel in our modern diet. Unnatural trans-fats (not all trans-fats, as there are natural ones such as conjugated linoleic acid (CLA), which appears to have significant health benefits) have been shown to be particularly evil, and a campaign has been waged (mostly successfully) to rid them from our modern diet. With unnatural trans-fats mostly out of the way, the worst of our modern novelties (in my opinion) is the excessive amount of linoleic acid (found in vegetable oils such as corn oil and soybean oil) in our modern diet. I could write a book about the evils of linoleic acid (who knows, maybe one day I will), but without going into detail, excess linoleic acid is associated with increased gut permeability, increased inflammation, and increased fatty liver, just to name a few conditions off the top of my head.  I think the westernized world would be a much healthier place if we would eliminate all the modern sources of linoleic acid and again embrace sources of omega-3 fats such as fatty fish and grass-fed meats (but that is enough information for another talk entirely!).

{Ed. Note- I can find it difficult to keep myself on task as I talk about evolutionary health. Since it really gives you a paradigm in which to think, it is so easy to branch off at any place to explore other venues that benefit from an evolutionary approach.}

When considering the declining health of the western world, other culprits in our modern diet are likely excessive sugars, additives and preservatives, soy, hyper-palitable processes foods, a host of other things I can’t think to list right now and, though it is debatable for some as mentioned above, grains and dairy.

Going beyond food- what else makes us human?

A topic that I have been meaning to write on for ages, but that “That Paleo Guy” Jamie Scott has recently been writing quite a bit about, is Sun.

Humans evolved outside, under the sun. Our lives, both daily and seasonally, were controlled by the rising and setting of the sun. Most of us know that UV radiation from the sun is responsible for starting the conversion of precursor compounds into active vitamin D, but how many of us actually get enough sun to be replete in vitamin D, and how much do we actually need? Looking at this from the evolutionary standpoint, we can determine that appropriate vitamin D levels are extremely important for human health and survival. Indeed- it is believed that the drive for adequate vitamin D levels is what drove lighter skin pigmentation in humans as they migrated away from the equator (lighter skin meant that people could still make adequate vitamin D despite the decreased UVB exposure at northern latitudes and the decreased skin exposure due to increased clothes in colder climates).

Vitamin D is also a great opportunity to tap into Ancestral Health as a way to guide modern medicine. For lack of a better description, we in the western world are shooting blind when trying to figure out what is an appropriate target for blood levels of vitamin D. We currently base our studies off of epidemiological studies of humans living well-outside their evolutionary niche and laboratory studies using isolated cells and models quite distant from a living, breathing, human.  While these studies can provide us with interesting information (and quite a bit of garbage), can it really give us a good idea of what is optimal for human health? Might information from people living in a traditional lifestyle give us a better idea of how humans have evolved to thrive? A paper recently came out that looked at vitamin D levels in groups of Maasai and Hadzabe and found that the mean Vitamin D concentrations in these population is 115nmol/L (~46ug/L) [2]. Whether this level is “ideal” is uncertain, but it’s an interesting (and arguably more reasonable) place to get started than trying to tease out a reasonable target from the varying levels of insufficiency in most modern civilizations.

The benefits of sunlight aren’t limited to vitamin D. The sun plays other roles in human health, and I will make a strong (personal) argument that sun exposure does wonders for psychological wellbeing!

Humans were meant to move

This is, perhaps, something that everyone can agree upon. This, like food and sun, is something that can be looked at from many different angles under the lens of evolution. How has our body evolved as we became bipeds, and where are the weaknesses in our constitution? Bipedalism changed the shape of our hips, and with it the risks of childbirth. Our shoulders are wonderfully mobile joints, but with mobility comes potential weakness (hello rotator cuff injuries!). And what about feet? Through feats (heh- couldn’t help myself!) of natural selection, our feet have been crafted over millennia to support and move us unassisted, yet now we want to rely on highly engineered shoes to cushion, balance, and protect our feet. Interesting research our of Harvard by Daniel Lieberman’s lab shows some of the effects shoes have on the forces exerted on our knees (cliff notes versions- shoes aren’t doing us any favors). Furthermore, recently the floodgates have opened letting loose a stream of research showing the “dangers of sitting”. These are all elements of human health that can be  more easily understood when placed in the context of an evolutionary paradigm.

Humans sleep

This seems like such an obvious statement, but it’s probably one of the hardest things for people to implement. As budding health professionals, we are rarely able to set a good example in this aspect, yet we should realize that cutting short on sleep is detrimental to more than just our coffee budgets. As I mentioned above, until recently, our lives were controlled by the rising and setting of the sun- now we are able to extend our hours (not just of waking, but also working), probably at great expense to our health. Here, as in other aspects of evolutionary health, I’m not recommending that we shun our modern world, but instead that we should understand our modern situation in the light of our evolutionary past and our biology. An interesting evo-health aspect to consider here is the effect of blue light on melatonin production (melatonin is a hormone important in controlling our circadian rhythm). Exposure to blue light decreases the production of melatonin in the brain, thereby affecting our sleep-wake cycle. While we’re unlikely to convince many (indeed you won’t convince me!) to turn my computer off after sunset, we should consider reasonable “hacks” to work around it. For this example, the cool free program f.lux is available, which alters the amount of blue light emitted from your display based on the time of day and your local sunset and sunrise time.  If you don’t have it already, check it out!

Humans have friends, not “friends”

I’m not going to waste much time on this one, but real, legitimate human interactions are an important part of being human. I’m not saying you can’t make great friends on the internet- one of my best friends is an internet friend- but a real social bonds take more time and effort than a 140 character message or the occasional “poke”.  Meaningful relationships take time, which is something many are painfully short of these days.  Alas, the same modern life stresses that make strong social bonds hard to forge and maintain also make such support even more necessary.


Evolutionary Medicine isn’t just about preventative health.

I won’t go into it here, but in the closing minutes of my talk I went on to talk about some of the evo-med examples I have written about here before. First I discussed the likely role of the appendix (and why we should care) and then I talked about an alternative perspective on the etiology of diverticulitis. I also stressed that this talk wasn’t meant to be an all inclusive “this is evolutionary medicine” talk, but more of an opportunity to introduce a subject that I hope my peers will start to consider as they continue their medical education and eventually head off to their specialty of choice.

I’ve only referenced a couple papers in this post, but I did put up a number of papers throughout my talk to show that this is science. There is a growing body of evidence to support the importance of evolutionary thinking in modern medicine, and an increasing interest in teaching evolutionary principles to medical students. As for me- I continue to find great excitement and joy (two wonderful human pleasures) in thinking about these evolutionary principles and how we can utilize them in practice.

1.            Varki, A., Nothing in medicine makes sense, except in the light of evolution. J Mol Med (Berl), 2012. 90(5): p. 481-94.

2.            Luxwolda, M.F., R.S. Kuipers, I.P. Kema, D.A. Janneke Dijck-Brouwer, and F.A. Muskiet, Traditionally living populations in East Africa have a mean serum 25-hydroxyvitamin D concentration of 115 nmol/l. Br J Nutr, 2012: p. 1-5.

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No- this isn’t an addendum to the “spring mating games” I mentioned in my last post.  (I feel like I might have just lost half my readers…)

The third year of medical school is a hectic one.  For those that aren’t familiar with the system, the first 2 years of medical school (in the US at least) are “pre-clinical” years, where future physicians learn the ‘basic science’ behind medicine. The foundations of our clinical knowledge are fields such as anatomy, embryology, biochemistry, pharmacology, physiology, pathology, microbiology, immunology, and, at least in my school, some basic biostatistics.  The end of second year culminates with the first step of the USMLE Boards.  Those that aren’t daft enough to take a hiatus to do a PhD (and when those of us that were daft enough finally come back) then start clinical clerkships in the third year.

For lack of a better description- 3rd year medical school is like speed dating for future physicians, but we’re looking for a career not a partner.  There’s a lot to be learned in third year (there is a very steep learning curve when you finally step foot on the floors), and each clerkship (Psychiatry, Neurology, General Medicine, Surgery, Obstetrics and Gynecology, Family Medicine, and Pediatrics) requires the acquisition of new clinical skills and knowledge.  The idea, obviously, isn’t to make you a surgeon in 2 months, but to give you some basic knowledge in these fields and to give you an idea of what it is like to be a physician in each of these specialties.

Some students come into medical school knowing what they want to be (though even the most determined often change paths), but many (myself included- more so at the beginning of medical school than now) really have no idea.  Over the course of a clerkship you not only get the basic clinical knowledge of a specialty, but you also get a feel for the specialty itself. These clerkships are short- I had a month on both Psychiatry and Neurology, and two months on Surgery.  This is barely enough time to figure out what a specialty is all about, and of course your experience is very much determined by the hospital you work at and the people you work with, yet this is the system in which we work (and in this instance I’m not sure there’s a better option).  By the end of third year, medical students need to know what they want to be “when they grow up”.  That’s when you have to start getting ready for “The Match”, the process in which medical students and residency programs rank their respective top picks and a computer determines their destiny (think of it as speed dating meets arranged marriage).

As I come off my surgery rotation, now a third of the way through my third year of medical school, it seems like an appropriate time to take a look at the clerkships past, and to glance forward to those awaiting me.

I started with Neurology- a very cerebral specialty (pun intended), where, at least when I spent my time with the stoke team, we spent a lot of time doing very thorough histories and physicals, teasing out the specific deficits and abnormalities of a patient’s presentation to determine (“localize” is the medical term) where in the brain there was an issue.  This is a wonderful exercise, and a skilled neurologist can take a thorough physical and, based on presentation, precisely localize where in the brain the problem has occurred… Now a day, this is frequently done as somewhat of an academic exercise after the determination has already been made by a CT scan and/or MRI. While there definitely is space for aspects of neurology to be explored with an ancestral/evolutionary health gaze (more hemorrhagic strokes during the winter? Maybe there’s a role for Vitamin D?), for me I found the specialty one of “a lot of thought, not much action”. Engaging as the thought process is, and as cool as some of the physical-exam detective work can be, I’m fairly sure that on my speed-dating card, Neurology is a “No”.

I was surprised by my Psychiatry clerkship. I wrote about my experience previously and, from the assessment of the clinicians I worked with and my own thoughts, I’d say Psychiatry is a mutual “Maybe”.

As I reach the end of my two-month trial on surgery, I will mark, without hesitation but with definite heartache, “No”.  Had my surgical rotation ended after my first month, when I had experienced only general surgery, there would have been no hesitation nor heartache.  General surgery is, without a doubt, not for me.  Over that month I saw many surgical revisions of the human body that were necessary, almost exclusively, because humans are living outside of an evolutionary appropriate lifestyle.  The removal of large portions of bowel because of diverticulitis, appendices and gallbladders removed around the clock, amputations because of uncontrolled diabetes… It all seems so unnecessary (for the most part) if we figured out how to live within the confines of how our body evolved to thrive.  In many of these cases, surgery is a (hopefully) definitive treatment for a preventable disease that I would rather just see prevented.  Other specialties within surgery- such as vascular, transplant, and cardiothoracic, or totally different training programs such as neurosurgery or orthopedics- all have their place, but none of them enthralled me. The other major issue with surgery is the toll it takes on your body and your life.  Surgery is physically demanding, not just for the hours of standing in one place, sometimes hunched precariously or stooped over a microscope, but also for the hours it requires.  Surgical training requires residents spend very long hours in the hospital, and to be honest, it’s not a price I am willing to pay.

The reason my rejection of surgery turned from an adamant “No” to a sorrowful one is because of Trauma.  My second month of surgery was spent with the Trauma team at my university’s hospital, a level 1 trauma center in a very rough inner city.  In many ways, Trauma surgery is the antithesis of neurology.  No- the people I was working with are not “just dumb trauma surgeons” as one of our attending physicians liked to self-deprecatingly refer to he and his collegues, but they are men (and women) of action.  There is a standard protocol that you run through when a trauma comes in, the “ABCs” (Airway, Breathing, Circulation, Disability, Exposure (yes, if you come into the trauma bay, you will lose your clothes)), but when something needs to be done, a trauma surgeon does not stand on protocol and wait for the final assessment. Many of the cases we saw in the trauma bay were definitely not “traumas” (simple falls, bar fights and assaults are generally things that should be taken care of in the Emergency Department), but many were full of the excitement and noise that years of watching ‘ER’ might have you come to believe is the norm.  One night on call I was part of the team that picked up a Motor Vehicle Crash (MVC) patient from the helipad on the hospital roof.  I’ve now seen gunshot wounds to all different parts of the body.  Trauma surgeons (or the good ones, as I witnessed in our hospital) know when to let assessment carry on, and when they’ve seen enough and something needs to be done NOW.

There is an urgency to trauma surgery, an element of intuitive action, that is lacking in other fields of medicine.  When you go to the operating room with a trauma patient you will see things you’ll never see in a hospital surgery patient, like the milky lymphatic ducts of the intestines (in all other surgery cases, patients are kept without food for many hours before surgery so their bowels (and the lymphatics which carry the emulsified fats we eat) are empty.). In trauma surgery, you’re working on a running engine.  Also, there’s often a significant element of “unknown” when you go to the OR with a trauma patient. These cases are time critical, and often the only imaging study you’ll have is a simple X-ray (no CT scan or MRI to tell you exactly what’s going on- there’s just no time).  A quick ultrasound may tell you there’s fluid in the belly, but you don’t know what that fluid is until you see it, and you don’t know where it’s coming from until you poke around for the source.  Trauma surgeons live in the moment- identifying, controlling, and treating acute injuries at times when minutes can make all the difference.

Another thing I like about trauma surgery, which is so different from general surgery, is that you are treating an acute incident that brings your patient to the table, not a chronic lifestyle (though one can argue that the lifestyle that many of our patients live is what is responsible for their trauma.  This is undoubtedly true for many or our MVC patients (please people- DO NOT DRINK AND DRIVE!) and some of our gun shot wounds and stabbings (we have quite a few repeat customers coming into our hospital for these injuries…).  There’s something about taking an acutely injured patient and ‘fixing them’ (or I prefer ‘putting them back together so they can heal’) that I enjoy that is missing in general surgery.

This feeling, however, comes at a cost.  The hours for any surgeon are long and arduous, but those of a trauma surgeon are longer and harder.  Yes, general surgeons get 3am consults, but a gunshot would to the chest is a lot more time-sensitive than an acute appendix or an obstructed bowel.  The lifestyle of a trauma surgeon is hard and it is wearing, and it obviously takes its toll.

Not surprisingly, trauma calls to a certain type of person… I loved the trauma surgeons- they were all so different: unique in their own ways and so obviously Trauma surgeons. During the last week (prior to my surgery exam) all the students (from all the different teams, about 30 of us in all- 5 had been on Trauma) were lectured by a number of surgical faculty.  You could always tell the trauma surgeons (even if they didn’t introduce themselves as such).  They lectured off the cuff- dynamic and fast.  None of them sat or stood by the computer flipping slides (if they used them)- they paced, gesticulated, called people out and made bold statements… They’re a little wild, often quick to act, and if I ever need a trauma surgeon, I’m really glad they are the way they are.

It was my experience on trauma, and with the trauma surgeons, that makes my heart ache a little bit as I check “No” for surgery. I know I could not mentally or emotionally hack the surgical residency (the hours and the years of all the other surgical specialties that you have to endure in order to do a fellowship in trauma). I also know that I will not put my body and my mind through the rollercoaster ride that is the call schedule of a trauma surgeon.  I know I need sleep. I know I need good food. I know I need sun and socialization.  But I will miss Trauma…

With 4 months and three specialties down, I look forward to my remaining 8 months and 4 specialties of third year.  As far as my speed-dating card goes, I think the best is yet to come. I don’t think Pediatrics, my next clerkship, will be the right fit, but I’m optimistic for the Family Medicine clerkship that follows and then the tour-de-force that is the Internal Medicine 4-month marathon.

When it comes down to it, I don’t think I’m going to find my perfect match in the speed-dating clerkships of medical school. Evolutionary medicine is a yet-to-be-defined specialty, and no residency program offers training in this field (though I have hopes for a fourth year elective in this area!). Indeed- just yesterday NPR mentioned evolutionary medicine and somewhat scathingly pointed out that it was not a practical discipline and at this point “only a theory”.

Actually, when it comes down to it, I don’t really think evolutionary medicine should be its own specialty… Much as it has been said that “nothing in biology makes sense except in the light of evolution”, I think “most (dare I say all?) issues of human health are best understood in the light of evolution”. You can find aspects of each specialty that would benefit from the keen focus of evolutionary minded individuals who, with careful thought, research, and synthesis of new ideas, could push the standards of medicine to new heights.

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