Low microbial diversity in the gut is associated with many diseases. Usually low diversity results from starvation of fiber, but conceivably supplementation with large doses of resistant starch could bring about a similar result.
I consider the optimal amount of fiber to still be an open research question. We don’t know the answer. But I am confident the optimal amount is not “infinite fiber.” There will be some amount that is too much.
Incidentally, getting a diversity of fiber types – not just resistant starch – will be important, as this too will promote microbial diversity. This is one reason a natural whole foods approach is likely to be optimal.
I agree with Jaminet's point. I think everyone should make an effort to eat a diversity of fibers.
But, I don't see 30-40g of RS to be an insane amount of RS. It's an amount you could find in nature. Here's how Tim Steele put it:
Tim Steele said:Here’s my take on 4TBS of [PS]. This is the amount found in one medium sized potato, a double handful of tiger nuts, one green plantain, a big chunk or wild yam. It’s not like inulin, where in order to get 40g you’d need to eat several pounds of raw onion or garlic. Of all the prebiotics, RS is the one found in the highest concentrations in nature, but we prepare the food in a way that destroys it. Tweaks in cooking can bring it back, if someone doesn’t want the accompanying calories or just want to really boost RS intake, [PS] is available.
I will be the first to say that a low-plant diet revolving around [PS] is a bad idea. [PS] should be used in a way that mimics a natural intake, ie. alongside other foods as in a smoothie or mixed in with mashed potatoes. I like to mix it in sour cream and put on a slightly cooled baked potato for instance. It should always be consumed with some natural fibers…psyllium husk and plantains have both been shown to increase the distal GI effects of [PS]. [LINK]
So, I think everyone agrees that lots of fiber diversity is optimal. But, as for excessive fiber, most of the coprolites (fossilized feces) of poo found from hunter gatherers show very high fiber intakes (such as 135g prebiotic inulin-type fructans per day!).
Additionally, scientists have found coprolites in the Hinds Caves that poop full of pollen (a natural form of raw prebiotic starch) with no other plant matter, which suggests they harvested the pollen and weren't just eating flowers.
http://ethnobiology.org/sites/default/files/pdfs/JoE/11-1/Reinhard.pdf
And the Hadza have been observed to consume between 75 to 100 grams of fiber per day, seven times the U.S. average, mostly from pulp and seeds of baobab fruits.
I doubt any of us will risk coming anywhere close to those HG fiber intakes with a few spoonfuls of fibers.
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