A new free-full text paper by Ian Spreadbury has been making the rounds lately. "Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity" is interesting because it is written through a distinctly Ancestral Health lens to provide a new framework for thinking about possible causes of Western disease.
For some time, many people in the Ancestral Health movement have blamed carbohydrates for various diseases of civilization, but over time, this idea has lost its hold and many writers in the movement now reject it. We perhaps have our own paradox- the "Kitavan paradox," which was probably the source for much of this questioning, particularly since so many paleo diet books in the past cited the Kitavan study and then told readers to restrict carbohydrates. This paper looks for reasons why
Despite food abundance and a clear overlap of macronutrients and glycemic index with Western diets, Kitavans are reported to possess leptin levels, fasting insulin, and blood glucose levels dramatically lower than those in Western populations deemed healthy, and appear to have a virtual absence of overweight, diabetes, and atherosclerotic disease.
What if it were something about grains per-se rather than carbohydrates? The paper describes how endotoxemia in the gut, particularly Lipopolysaccharide (LPS), can lead to systematic inflammation related to many elements of metabolic syndrome like leptin resistance. Endotoxins are part of the cell-wall in gram-negative bacteria such as E.Coli and Salmonella and they provoke an inflammatory response in many contexts. The idea here is that Western diets perhaps might increase endotoxemia by promoting growth of pathogenic bacteria and adding fuel to the fire by increasing intestinal permeability, allowing endotoxins to ply their inflammation across the entire body. He also mentions the fact that science is showing that this process occurs in the mouth as well, where modern diets promote "leaky teeth" aka gingivitis, which has convincing ties to metabolic syndrome (which pilot studies show a paleo diet might treat).
Unfortunately, we then develop another paradox because most of the studies on LPS in humans show that absorption is promoted by a high-fat diet. And as the paper notes, foraging peoples with higher fat diets do not seem impaired.
Maybe their microbiota protects them and as I've written before, carbohydrate consumption can affect the composition and function of gut bacteria.
Spreadbury lays out a hypothesis that carbohydrates can be divided into two groups. Cellular carbohydrates, which are:
Tubers, fruits, or functional plant parts such as leaves and stems store their carbohydrates in organelles as part of fiber-walled living cells. These are thought to remain largely intact during cooking, which instead mostly breaks cell-to-cell adhesion. This cellular storage appears to mandate a maximum density of around 23% non-fibrous carbohydrate by mass, the bulk of the cellular weight being made up of water.
Then there are the acellular carbohydrates:
The acellular carbohydrates of flour,94 sugar and processed plant-starch products are considerably more dense. Grains themselves are also highly dense, dry stores of starch designed for rapid macroscopic enzymic mobilization during germination.95 Whereas foods with living cells will have their low carbohydrate density “locked in” until their cell walls are breached by digestive processes, the chyme produced after consumption of acellular flour and sugar-based foods is thus suggested to have a higher carbohydrate concentration than almost anything the microbiota of the upper GI tract from mouth to small bowel would have encountered during our coevolution.
And here we have another problem. Because archeologists continue to find earlier and earlier evidence of what was once considered advanced food processing, from pottery to grind stones. The foods that are characterized as "acellular"...well, how long have they been in the human diet? The paper mentions some of these finds, but says they were likely a small part of ancient diets, but that is far from a sure thing. We also have an ethnographical gap here in this chart:
Because you can see modern processed foods there, but nothing on indigenous "processed" foods. No chicha or poi or any of the variety of ground/fermented/pounded foods that many of these cultures consume. This is partially because there is very little data on these foods, which is unfortunate.
My prediction is that better accounting of indigenous diets will show that they consume more of the acellular carbohydrates than initially predicted by some. We also need ethnographical data that records everything consumed, even things that seem incidental like teas.
But I think we need to look further into the types of these consumed and other compounds they contain. Same for fatty foods.
An interesting thing here (thanks Stabby the Raccoon) is that studies show that orange juice, a accellular carbohydrate, reduces endotoxin load. Orange juice is one of those things you probably thought was healthy and then you realized it had sugar and it was "bad" and now people are rediscovering it again. But I think the sugar here is incidental, what is probably more interesting is the ability of antioxidants to suppress endotoxins. Wine and olive oil may have similar properties.
I was browsing The Human Food Project's website and came across a letter written by anthropologist Jeff Leach on low-carb diets:
In a series of elegant studies, Cani and colleagues ( 2-4) have shown that holding calories constant and varying macro levels of fat can induce low-grade metabolic endotoxemia which can lead to complications associated with cardiovascular health. As fat intake, so do serum levels of LPS and associated biomarkers. However, in high-fat diets with prebiotic oligosaccharides added (derived from chicory roots), serum levels of LPS drop, as do the metabolic markers of inflammation.
So it is also possible that prebiotics in indigenous diets also have a protective effect. So we shouldn't look so much perhaps at dividing carbohydrates into two categories, but tracing each type of carbohydrate to the type of bacterial environment it promotes.
Now n=1 time here, but I had gingivitis before I started eating better and it went away. And all the sudden it came back. And it was incredibly frustrating. Frustrating to the point that I even thought the problem might have been caused by the cavity-ridden guy I had started dating when my gums got bad again for giving me his lame mouth bacteria. I started supplementing a few things, notably K2, D3, and switched back to the flax oil that I had been using when my gums were better. The problem resolved and has not come back and my gums even survived the breakup with bad-teeth guy despite the fact I was eating mainly ice cream. So I don't know if for me, it was more about nutrients I needed to get rather than too much simple sugar.