Sunday, June 26, 2011

Carbohydrate Shortage in Paleo Land: New Data for A Scientific Outlook at the Low-to-No Carb Paleo Confusion. Will More Than 125g of Carbs Make You Fat?

Image 1: Salmon, one of the few foods,
even the extremists allow themselves
(photo by Dezidor)
"Do you [eat] Paleo?" Over the last years, the "Paleo lifestyle", once some sort of esoteric "back to the roots" movement, has attracted more and more followers and has long become a multi-million dollar business. Somewhere in the course of this process, however, the original idea, which was to look at the nutritional history of humanity to identify those nutritional strategies that have been working for humanoids for ten-thousands of years, got lost. Mainstream paleo has turned into an obscure cult the members of which add food item after food item to their lists of "bad foods", the consumption or rather non-consumption of which distinguishes the "real" from the 99% paleo-eaters. Yet, while eating gluten-containing (the paleos would probably say "contaminated") foods has, probably not without reason, been considered a deadly sin, all along, carbohydrates in general have only recently moved up in the ranks of the worst offenders of a neolithic paleo-lifestyle. Being infiltrated by renegades from the low-fat and low-carb camps the Paleo diet is misinterpreted by more and more of its followers (mostly children of the fat-phobic 1980s) as a high protein, low-fat, no-carb diet. Looking at this unfortunate trend one could certainly go nuts, if, yes if nuts had not been added to the paleo-food-ban-list, lately, as well...

Oh, before I forget. This is not another pro- or anti-paleo carb or paleo blog, but the SuppVersity - so let's try to tackle the low-to-no carb conundrum from a somewhat more scientific perspective. Only very recently Alexander Ströhle and Andreas Hahn (Ströhle. 2011) have published a paper in Nutrition Research, in which the authors take another, closer look at the purportedly low carbohydrate content of THE paleolithic diet. In that their most relevant finding unquestionably is that the "diets of hunter-gatherers showed substantial variation in their carbohydrate content". So, even if the ludicrous assumption that the way our ancestors ate would be the "optimal" way to eat for us held true, we still would not know whether this "optimal" diet would contain <3% or >50% of our daily caloric intake in the form of carbohydrates, for these are the variations Ströhle and Hahn found for different ecoenvironments.
Figure 1: Average minimal and maximal carbohydrate content of the diet of paleolithic individuals living at different latitudes; data in %-age of calorie consumption (based on data from Ströhle. 2011)
As the illustration in figure 1 shows, it would largely depend on how far from the equator your ancestors lived, whether you would strive on an Inuit diet with <5% carbohydrate or mimic the mediocre carbohydrate intake of a Mediterranean diet. Yet, wherever your grand-grand-grand-parents may have come from, one thing is almost certain: following one of the official guidelines depicted in figure 2 will certainly provide way more energy from carbohydrates than what the paleolithic part of your genome will be able to tolerate.
Figure 2: Recommended (mean) carbohydrate intake in %-age of total calorie consumption
(data adapted from Ströhle. 2011)
If you have a closer look at who suggests what, you may notice that the WHO and the US Food and Nutrition Board propagate the (ridiculously) highest amounts of carbohydrates. Well, consider this: The WHO is hardly able to feed all their members even when they use the cheapest among the cheap nutrients, which obviously are carbohydrates, and the US have got to get rid, ahh... I mean, sell their annual production of  more than 256,900,000 metric tons of corn to somebody... what? "Scandal"? No, I didn't say that...

But let's put this hot topic aside and get back to the issue at hand and ask our selves: "How low-carb was the paleo diet, then?" Well, 22% of a 2.000kcal diet would still be 440kcal, which is equivalent to 110g of carbs, which is at the upper end of the low-carb continuum (ranging from 50-130g of carbs per day), as it was proposed by Accruso et al. (Accruso. 2008) and that is far from no-carb or recommendations <80g, where it becomes increasingly hard to find nutrient dense foods, the sum of which would not exceed your daily carbohydrate limit. Maybe I should add, that it is by no means accidentally that the limit appears to be somewhere around 500kcal. A 1988 overfeeding and depletion study by Acheson (Acheson. 1988) reports that  "an average male human being canaccommodate a gain of approximately 500 g before net lipid synthesis contributes to increasing body fat mass". So even within the upper ranges (and without exercise!) you are way below the fat storage zone. Under circumstances of continuous glycogen depletion such as exercise training, which go hand in hand with severe muscle and liver glycogen depletion, you may well be able to tolerate much higher amounts of glucose, because overall, your body is able to store roughly 5 g glucose per kg of body weight. So, once carb-depleted (notice: 100% carb depletion is a state you will not achieve; probably not even by running a marathon) an 80kg human being could safely refuel on 400g of carbs or 1.600kcal without running the risk of overloading his glycogen stores.
A note of caution: 400g of pure glucose, especially when taken on a regular basis, could have metabolic side effects unrelated to the overflow of glycogen stores that you better want to avoid; the same (better avoid) is true for fructose, as it is metabolized into triglycerides by the liver and will refuel your glucose stores only indirectly, if it is not previously taken up by adipose tissue.
All these arguments aside, it is also noteworthy that the restriction in carbohydrates, our ancestors practiced, was by no means self-inflicted, it exhibited great seasonal varieties and there is NO proof whatsoever that a higher carbohydrate intake - of course in the form of those whole foods that were available to the paleolithic individuals - would have made them more susceptible to "modern disease" - but this would be whole other blogpost. And let's be honest without your highly processed breads, cakes and pies, your high-fructose corn-syrup laden sugary drinks and all the pasta, pizza and rice the restaurants serve in order to keep you from noticing that they economized all the expensive stuff such as meat, vegetables and fruit, you probably would not even get beyond the 35%-margin Ströhle and Hahn identified at the maximal (seasonal mean) carbohydrate intake in across various hunter-gatherer populations, and latitude and ecological environments. And isn't it ironic, that the very sweet tooth that kept our ancestors alive, is killing us today.