Monday, May 28, 2012

How Bad is Fructose? David Despain Interviews Dr. John Sievenpiper

In my article "Is Sugar Fattening?", I discussed a recent review paper on fructose, by Dr. John Sievenpiper and colleagues (1).  It was the most recent of several review papers to conclude that fructose is probably not inherently fattening in humans, but that it can be fattening if it's consumed to excess, due to the added calories.  Dr. Sievenpiper and colleagues have also written other papers addressing the metabolic effects of fructose, which appear to be fairly minor unless it's consumed to excess (2, 3, 4, 5).  The senior author on these studies is Dr. David Jenkins at McMaster University.  David Despain, a science and health writer who publishes a nice blog called Evolving Health, recently interviewed Dr. Sievenpiper about his work.

It's an interesting interview and very timely, due to the recent attention paid to fructose in the popular media. This has mostly been driven by a couple of high-profile individuals-- an issue they discuss in the interview.  The interview, recent papers, and sessions at scientific conferences are part of an effort by researchers to push back against some of the less well founded claims that have received widespread attention lately.

Read more »

Monday, May 21, 2012

Lower Blood Pressure Naturally

Recently, Chris Kresser published a series on dietary salt (sodium chloride) and health (1).  One of the issues he covered is the effect of salt on blood pressure.  Most studies have shown a relatively weak relationship between salt intake and blood pressure.  My position overall is that we're currently eating a lot more salt than at almost any point in our evolutionary history as a species, so I tend to favor a moderately low salt intake.  However, there may be more important factors than salt when it comes to blood pressure, at least in the short term. 

Read more »

Thursday, May 17, 2012

Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part III

In previous posts, I reviewed some of the evidence suggesting that human evolution has accelerated rapidly since the development of agriculture (and to some degree, before it).  Europeans (and other lineages with a long history of agriculture)  carry known genetic adaptations to the Neolithic diet, and there are probably many adaptations that have not yet been identified.  In my final post in this series, I'll argue that although we've adapted, the adaptation is probably not complete, and we're left in a sort of genetic limbo between the Paleolithic and Neolithic state. 

Recent Genetic Adaptations are Often Crude

It may at first seem strange, but many genes responsible for common genetic disorders show evidence of positive selection.  In other words, the genes that cause these disorders were favored by evolution at some point because they presumably provided a survival advantage.  For example, the sickle cell anemia gene protects against malaria, but if you inherit two copies of it, you end up with a serious and life-threatening disorder (1).  The cystic fibrosis gene may have been selected to protect against one or more infectious diseases, but again if you get two copies of it, quality of life and lifespan are greatly curtailed (2, 3).  Familial Mediterranean fever is a very common disorder in Mediterranean populations, involving painful inflammatory attacks of the digestive tract, and sometimes a deadly condition called amyloidosis.  It shows evidence of positive selection and probably protected against intestinal disease due to the heightened inflammatory state it confers to the digestive tract (4, 5).  Celiac disease, a severe autoimmune reaction to gluten found in some grains, may be a by-product of selection for protection against bacterial infection (6).  Phenylketonuria also shows evidence of positive selection (7), and the list goes on.  It's clear that a lot of our recent evolution was in response to new disease pressures, likely from increased population density, sendentism, and contact with domestic animals.

Read more »

Monday, May 7, 2012

Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part II

In previous posts, I described how Otzi was (at least in large part) a genetic descendant of Middle Eastern agriculturalists, rather than being purely descended from local hunter-gatherers who adopted agriculture in situ.  I also reviewed evidence showing that modern Europeans are a genetic mixture of local European hunter-gatherers, incoming agricultural populations from the Middle East, neanderthals, and perhaps other groups.  In this post, I'll describe the evidence for rapid human evolution since the end of the Paleolithic period, and research indicating that some of these changes are adaptations to the Neolithic (agricultural/horticultural/pastoral) diet.

Humans have Evolved Significantly Since the End of the Paleolithic

Evolution by natural selection leaves a distinct signature in the genome, and geneticists can detect this signature tens of thousands of years after the fact by comparing many genomes to one another.  A landmark paper published in 2007 by Dr. John Hawks and colleagues showed that humans have been undergoing "extraordinarily rapid recent genetic evolution" over the last 40,000 years (1).  Furthermore:
Read more »

Saturday, May 5, 2012

Media Appearances

Last October, I participated in a panel discussion organized by the Harvard Food Law Society in Boston.  The panel included Drs. Walter Willett, David Ludwig, Robert Lustig, and myself, with Corby Kummer as moderator.  Dr. Willett is the chair of the Harvard Department of Nutrition; Dr. Ludwig is a professor of nutrition and pediatrics at Harvard; Dr. Lustig is a professor of clinical pediatrics at UCSF; and Kummer is a food writer and senior editor for The Atlantic
Read more »

Saturday, April 28, 2012

Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part I

In the previous post, I explained that Otzi descended in large part from early adopters of agriculture in the Middle East or nearby.  What I'll explain in further posts is that Otzi was not a genetic anomaly: he was part of a wave of agricultural migrants that washed over Europe thousands of years ago, spreading their genes throughout.  Not only that, Otzi represents a halfway point in the evolutionary process that transformed Paleolithic humans into modern humans.

Did Agriculture in Europe Spread by Cultural Transmission or by Population Replacement?

There's a long-standing debate in the anthropology community over how agriculture spread throughout Europe.  One camp proposes that agriculture spread by a cultural route, and that European hunter-gatherers simply settldd down and began planting grains.  The other camp suggests that European hunter-gatherers were replaced (totally or partially) by waves of agriculturalist immigrants from the Middle East that were culturally and genetically better adapted to the agricultural diet and lifestyle.  These are two extreme positions, and I think almost everyone would agree at this point that the truth lies somewhere in between: modern Europeans are a mix of genetic lineages, some of which originate from the earliest Middle Eastern agriculturalists who expanded into Europe, and some of which originate from indigenous hunter-gatherer groups including a small contribution from neanderthals.  We know that modern-day Europeans are not simply Paleolithic mammoth eaters who reluctantly settled down and began farming. 

Read more »

Tuesday, April 24, 2012

Lessons From Ötzi, the Tyrolean Ice Man. Part III

There are two reasons why I chose this time to write about Otzi.  The first is that I've been looking for a good excuse to revisit human evolutionary history, particularly that of Europeans, and what it does and doesn't tell us about the "optimal" human diet.  The second is that Otzi's full genome was sequenced and described in a recent issue of Nature Communications (1).  A "genome" is the full complement of genes an organism carries.  So what that means is that researchers have sequenced almost all of his genes. 

Read more »