Friday, May 9, 2008
Survival of the Sickest
I am reading this fascinating book on evolutionary medicine that's turning up stunning facts. "Survival of the Sickest" is written by Dr Sharon Moalem who has a PhD in neurogenetics and human physiology. He's probing if some of our hereditary diseases today might have been evolution's response to bigger problems way back when.
I know this is odd in a food blog but I'll include examples of food/dietary-linked diseases here (I'm really doing them a disservice by such short summaries - the book devotes entire chapters to them!):
Hemochromatosis, a condition that keeps too much iron in the system, may have helped carriers tackle the deadly Bubonic plague by locking away iron that the bacteria needed in order to flourish.
Diabetes might have saved humans during the last ice age 11,000 years ago. Sugar is a natural antifreeze (lowers the freezing point of any liquid it's in), so bodies that released a lot of it into the blood system could continue to function in extremely cold weather. Didn't the sugar damage the organs like in modern-day diabetes? No, it probably never reached dangerous levels because the body used it (burnt directly by brown fat as fuel) to generate body heat. Dietary sugar, too, was likely scarce.
Oh and by the way, climate change can and did happen very rapidly in the past too - scientists are now just discovering examples - the last ice age took mere decades to happen.
And why are some of us more prone to have higher cholesterol in our systems? Guess what? The sun converts cholesterol in our body to Vitamin D. So where there's inadequate sunshine (e.g. Northern Europe), the body cranks up cholesterol for Vitamin D production. But dark-skinned African Americans are also prone to high cholesterol. Their dark skin was evolved to protect the body against too much UVB light penetration, which destroys folate (critical for healthy brains and babies). But that also limits Vitamin D production, so what to do but crank up more cholesterol for that purpose. I say, this is helpful info! Instead of taking statins (anti-cholesterol drugs which are generally safe but can cause liver damage in the long run), you can hit the beach and tan some excess cholesterol away!
Probably the most stunning revelation is how a huge percentage of human DNA is related to...VIRUSES! Yes, we've got viral DNA written into ours - retroviruses which aren't harmful, thankfully. They're hitching a ride in our system, but in return, we've benefitted from their ability to mutate quickly. The human genome is not a static blueprint. We've got DNA transposons (jumping genes) that are constantly doing a copy/cut-and-paste dance all over the place, to cope with environmental stresses and demands. Maybe it's them that's allowed us to "evolve" to what we are today, away from our furry primate cousins. But I can't help but think of what Agent Smith said in The Matrix - that humanity is like viruses. How true in more ways than one!
There's SOOO much more (oh I love the aquatic ape theory too). Overall, the book challenges the medical field to use this new info to find new ways to fight disease, e.g. fighting infection by limiting access to iron, and directing viral evolution away from virulence, instead of an escalating arms race where superbugs keep emerging as victors.
Written in a lively, animated manner, the book is incredibly easy to read. You can finish it in a day. But it's so packed with interesting gems that I started re-reading it before I finished it!
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