And I mean A LOT more. If statistics are to be believed, you, the reader, are almost undoubtedly not meeting the USDA's recommendation. Worse still, I have concluded that the USDA daily fiber recommendation is inadequate.
I will attempt to be brief and not boring, but I'm not promising anything. Our digestive tract is much smaller, as a function of body size, than the tracts of our primate cousins. Chimps, gorillas, orangutans, all of them have massive digestive tracts. Truly, we have one of the smallest digestive tracts in the entire animal kingdom. Look at snakes; they're a giant, mobile intestine with a mouth!
No one has ever found this odd since animals eat a very rough diet. Snakes spend their time digesting whole, unchewed rats, and chimps spend the bulk of their time eating leaves, branches, some fruit, and the occasional piece of meat. For a long time, everyone assumed that our digestive tracts changed over evolutionary time by virtue of our ability to find higher quality foods, and eventually nutrient-dense meat which we were able to masticate and more quickly process in comparison to other meat eaters.
This perspective was supported with the analysis of primates that either carefully choose high-quality foods, like Baboons, or consume a huge amount of animal matter, such as monkeys that eat bugs. The digestive tracts of these animals, both in structure and size, are very similar to human digestive tracts.
This perspective changed slightly when researchers started finding that a raw diet doesn't provide enough nutrients for a proto-human duking it out with other animals on the plains of Africa. Even with meat included in the hypothetical diet, there simply wasn't enough energy to support significant populations of large, upright omnivores. While it's still somewhat controversial, an increasing number of researchers are accepting that the real change, the change that pushed us beyond anything that the Earth had yet seen, was cooking.
Heating food breaks down all of the chemical bonds that our digestive tracts would have otherwise needed to break, making the extraction of nutrients much easier. This results in a higher "net" gain, where your body must expend less energy to do the digesting. Cooking unlocked massive untapped reserves of calories that no other animal had ever had.
A few generations later, and bam, we had a more-or-less modern human digestive tract. From this point on, it was always assumed that the digestive tracts of humans and higher primates were functionally different, but no one ever did any real research until the late 80's and early 90's. It was then that they found that, on a functional level, the tracts of chimpanzees and humans were nearly identical. We digest food the same way, our tracts are simply smaller.
Now here's a fun fact about the chimp diet: they eat a ridiculous amount of fiber. Hundreds of grams per day. They can do this because they spend damn-near every waking hour eating. All of the dietary benefits that one can expect from this are probably accounted for in chimp physiology, and it gives us insight into our own functioning.
Fast-forward to 6:45 for the part where humans try to eat a chimp diet.
The question, of course, is whether imitating chimp diets vis-a-vis fiber intake is a good idea. I think that it is. The USDA recommends 25-30 grams of fiber per day. This doesn't include a breakdown of soluble and insoluble, which I will discuss in just a moment.
If the chimp digestive tract evolved to process buckets of fiber, so did ours. Chimps eat hundreds of grams of fiber per day. The average American eats less than eighteen. Obviously, humans cannot process the amount of fiber that chimps can, but no matter how far our digestive tract have moved from chimps, these numbers cannot be reconciled.
Fiber works in two ways. The soluble fiber breaks down, it ferments, in the body and binds with a wide array of chemicals in the the digestive tract and in the blood stream. It attenuates blood sugar spikes, drops cholesterol levels, and normalizes lipids. Truly, soluble fiber has so many benefits, researchers are finding new ones every year.
Insoluble fiber is the fiber that simply passes through the digestive tract. It's mode of function isn't completely understood, but it's assumed that it physically scratches the interior of the digestive tract, increasing fluid production and digestive action. The more fiber you eat, the faster you digest.
This has an equivalent in the chimp world, where chimps' digestive systems respond to varying fiber levels as an indicator of the outside world. Low fiber levels indicate nutrient dense, fresh foods at the beginning of the growth season. The digestive tract slows down to extract more nutrients from these foods. As the foods mature and become harder to digest, the fiber levels rise. The digestive tract responds by speeding food through the system more quickly to allow the chimp to eat more.
Not only are humans eating the most nutrient-dense food in the history of the world, but our fiber content is so low that our digestive systems are taking their sweet damn time about it. We are getting every calorie possible from those Pop-Tarts and this is undoubtedly contributing to our increasing weights.
You may have heard that high fiber intake can have a negative effect on nutrient absorption. Not only is this true to a degree, it's absolutely expected. If high fiber causes our bodies to push foods through our system more quickly, not absorbing all of the food is the point. We live in a world of such extreme plenty, getting the required nutrients is easy. The problem is getting too many of them.
I think that a person's dietary life should revolve around fiber intake. Everyone should get at least 100% of their fiber via food, and this is easy! Two slices of Double Fiber bread from Arnold provides half of your daily requirement. Two tablespoons of peanut butter provides 20%. A single PB&J sandwich and you're three-quarters of the way there. One sandwich!
Integrate beans into your diet at some point during the day and you've easily met your 25-30 gram target. Once you have done this, exceed your target with supplements and special foods. For example, Fiber One cereal gives you 28g of fiber in one cup. Mix it with strawberries and blueberries and you have a fiber-rich super meal.
Add Metamucil to everything that you cook or make. Add it to sauces, add it to drinks, add it to water. Metamucil has a distinct advantage over other forms of fiber in that it is easy to use and 50/50 soluble and insoluble fiber. The startling list of benefits from soluble fiber will likely only grow, so you might as well get on that bandwagon now.
I need to address the claim posited by many vegetarians, most vegans, and essentially all raw food consumers: the human digestive tract is so similar to other primates that we should be eating their diet. This is stupid.
Functionally, our systems are very similar, but structurally they are very different. It is not just the length of our tracts that is different, but the ratio of large to small intestine. Moreover, these vegetarian claims also seem to ignore that chimps will eat as much meat as they can manage, usually unlucky monkeys and bush babies.
Every bit of research done indicates that we have been eating meat for millions of years and that our diet must be different from other primates for us to thrive. I am not talking about the removal of meats, cheeses, and Pop Tarts from the diet, I'm simply saying that our digestive tracts evolved to handle much larger amounts of fiber than we are currently giving them. Along with all of the other things that we want, increased fiber intake is critical.
I forgot to add that with increased fiber comes increased water. If you don't ensure that you are drinking 8oz of water every two hours, not only will the fiber be less effective, you might actually increase your chances for constipation.