Tuesday, August 02, 2011

Another Bad Journalist Examines the Paleo Diet

By Monica

Another article has come out attempting to discredit the Paleo diet, this time in The Atlantic. If you can get all the way through it without your blood pressure and cortisol rising, you're have more patience than I do.

Let's address some of the shoddy scholarship.

Life Expectancy

The author credits agriculture for increases in lifespan. Is this true? I became very interested in the issue of lifespan over a year ago and set out to look at US longevity figures myself (US National Center for Health Statistics. National Vital Statistics Reports, Births: Fina Data for 2004).

Here are some life expectancy figures to chew on.

paleolithic: 30
1900: 47.3
1915: 54.5
1940: 62.9
2002: 77.3

Infant mortality has dropped like a stone. Between 1915 and 2002, 6 of the 22.8 years of gain in life expectancy are due to reduction in infant mortality alone. Undoubtedly, most of the increase in lifespan since 1900, including reduction in infant mortality, is due to modern plumbing and sanitation. The fact that life expectancy was 62.9 in 1940, before the widespread use of penicillin or even the Green Revolution, is remarkable.

Agriculture? For the ten thousand years or so between the paleolithic to the year 1900 we gained 17.3 years in life expectancy. That's a long time with not much to show for it. That's post-Industrial Revolution, too. What was life expectancy in 1600?

Excluding infant mortality, even the Native Inuit living without the benefit of any western medicine or technology in mid-1800s had an average life expectancy of about 43 years after being exposed to foreigners carrying diseases. The life expectancy figures are similar for paleolithic people, who suffered from high infant mortality, trauma, warfare, and zoonotic disease: around 30 before infant mortality, and around 45 with infant mortality eliminated. Their lack of life expectancy didn't have anything to do with the food they ate.

The data actually show a slight drop in life expectancy after the adoption of grains, and a bigger decline in dental and skeletal measures of health. None of this was unknown in the 1930s when nutritionists routinely referred to the diets of primitive people as better than our own. Now, journalists who can't pull out government health statistics and use some logic can get away with crediting a nearly 30 year life expectancy gain, over the course of a century, to agriculture rather than technology in agriculture, medicine, and sanitation.

Carbohydrates

Paleodiets were not low in carbohydrates and according to the most recent estimate in the peer-reviewed literature -- by two experts who have been writing paleodiets long before preconceptions about them hit the popular press -- were anywhere from 30-65% carbohydrate, rivalling the carbohydrate intake of modern Americans. Does that sound like Atkins? I don't think so. So why is this journalist making a comparison to Atkins?

Many paleodiet advocates do not posit that carbohydrates are problematic. There may be, however, a big problem with gluten grains. The wheat of today is not the same wheat of 100 or 150 years ago, and some people with gluten intolerance can even eat ancient Einkorn wheat. Most wheat 150 years ago was sourdough fermented for days to weeks, which apparently reduces gluten content significantly since some gluten-sensitive people can handle it. Nevertheless, despite lower gluten content in early grains, they are still a poor source of micronutrients, which is evidenced by the negative selection pressure it placed on humans, as evidenced in the skeletal record of health, linked above.

Scarcity

Most modern hunter gatherers, who deal with scarcity far above what our paleolithic ancestors dealt with due to large animal extinctions and being forced onto marginal habitat, spend about 20 hours weekly gathering foods. If they were dealing with scarcity they would be spending far more time gathering foods. Abundance and scarcity of foods are probably not the issues so much as seasonality. There are plenty of reasons I wouldn't want to live their life. But modern hunter gatherers are not starving.

Healthy or Not?

The article makes reference to paleodiets being potentially "unhealthy fads" in its title and then concludes with a whole paragraph on how healthy the paleodiet actually is. According to the author, it's a "powerful meme" but only extreme health nuts can follow it. Which is it? Healthy or unhealthy? Bait and switch.

The other thing that bugs me about this article is that "Paleo man," if we're talking about upper paleolithic humans, looked just like us, not the 5 million year old Homo erectus which is shown at the top of this article.

"US News"

Old news at this point, but US News ranked the Paleo diet last in a recent ranking of popular diets. This journalist mentions that ranking but is apparently unaware of the excellent rebuttal recently written by Loren Cordain and colleagues that actually makes dozens of references to scientific literature instead of pulling preconceived ideas from thin air.

It's too bad to see such an irresponsible example of journalism in The Atlantic. Unfortunately, a lack of scholarship and critical thinking surrounding paleodiets just seems de rigueur.

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