A new study was just published on the health effects of a low-carb/high-fat (LCHF) diet in mice. http://www.nature.com/nutd/journal/v6/n2/full/nutd20162a.html.
It has been getting a lot of media attention with headlines touting things like
“New study says Paleo diet ‘unhealthy and fattening’ angering ardent devotees”.
The above was from the Telegraph: http://www.telegraph.co.uk/news/worldnews/australiaandthepacific/australia/12164394/New-study-says-Paleo-diet-unhealthy-and-fattening-angering-ardent-devotees.html.
Given that a LCHF paleo style diet (PSD, more primal due to inclusion of dairy products), I was skeptical, so I downloaded the paper and supplementary table.
Turns out I had a right to be skeptical.
Exhibit A: From the methods section: “The carbohydrate content of the LCHFD was exclusively derived from simple sugar (sucrose: 106 g kg−1)”
Doh! what a major flaw in this study! A healthy LCHF PSD like the one I and many of my friends and colleagues follow minimizes natural or added sugars, especially from refined sources like sucrose, and the relatively small portion of carbohydrates we DO include in our diets are from whole-food sources and tend to be of the complex starch variety, such as tubers, plantains, root vegetables (beets, carrots, etc.), and some fruit (in moderation). That is, we follow a WHOLE FOODS diet from ingredients that receive relatively low amounts of processing.
The diet used by the researchers was made of very highly processed ingredients. I’ve published evidence in a wild-type rat model showing that it is the degree of processing, irrespective of macronutrient ratio, that seems to be heavily implicated in health outcomes, including cognitive function: http://www.sciencedirect.com/science/article/pii/S0031938414000833.
Here’s the supplementary table showing the actual ingredients they used in their study:
The ingredients were mostly derived from highly processed sources. For example, the protein comes completely from casein, which has been shown to make mice highly susceptible to aflatoxin-induced cancer: http://www.westonaprice.org/our-blogs/cmasterjohn/the-curious-case-of-campbells-rats-does-protein-deficiency-prevent-cancer/. Hat tip to Chris Masterjohn for his detailed analysis of this literature.
Exhibit B: the mice used in the study were genetically modified to develop obesity. This is the topic of a whole other blog post, but it is often the case that mice that have been genetically modified to mimic a disease or disease process found in humans, turn out not to be a good model for the mechanism of the disease in humans.
Exhibit C: perhaps even wild-type mice would be a bad model for studying the health effects of a diet for humans because they are adapted to quite a different dietary niche than are humans. A great argument for this has been made by my friend and colleague Richard Feinman: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3488544/.
They summarize in their abstract: “In sum, the response of mice to a carbohydrate-free diet was greater weight gain and metabolic disruptions in distinction to the response in humans where low carbohydrate diets cause greater weight loss than isocaloric controls. The results suggest that rodent models of obesity may be most valuable in the understanding of how metabolic mechanisms can work in ways different from the effect in humans.”
This statement matches my own observation in the effect of a LCHF PSD in myself and others (though not everyone, which is an important point that we should not discount individualized approaches to diet and health).
Of course the news stories everywhere are claiming “Paleo diet shown to be harmful!”.
Professor Aaron P. Blaisdell