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What is fiber and why is it beneficial?
What is fiber and why is it beneficial?
If you are eating vegetables, fruits, and whole grain products, you are surely consuming fiber too. Dietary fiber is edible parts of plants that cannot be digested by human enzymes and therefore can't be absorbed in the human small intestine.
Dietary fiber is most often classified as soluble and insoluble fiber. As the names indicate, the first is soluble in water, and the second isn't. As a result, both have different properties in cooking and digestion, as well as have different health effects.
I. Soluble Fiber
Soluble fiber can create a gel. For example, when making jam, the soluble fiber pectin is released into the surrounding liquid and gels it up. Something similar happens in the gut, where it creates a gel that can "entrap" or slow down the movement and absorption of some compounds and nutrients. Because of this, it can:
• Slow down food transit from the stomach to the intestines, keeping you feeling full longer and slowing down absorption.
• Slow down sugar absorption, helping to avoid sugar spikes and regulate blood sugar levels.
• Entrap bile acids that would normally be reabsorbed and contribute to the cholesterol pool, thus helping to reduce cholesterol levels.
Examples of soluble fibers are pectin, FOS, GOS, inulin, and gums (e.g., β-glucans, galactomannans, arabinoxylans).
II. Insoluble Fiber
Insoluble fiber binds water, increasing the mass of the non-digested matter. Because of this, it can:
• Speed up the transit time and prevent or help with constipation.
Examples of these are cellulose, hemicellulose, and chitin.
Some fiber such as resistant starch has some soluble and insoluble fiber properties.
There are both soluble and insoluble fibers that can:
• Function as prebiotics. Since dietary fiber is not digested in the small intestine, it makes its way to the large intestine, where some of it can be digested by the gut microbiota, giving them a real feast!
• Be found in vegetables, fruits, and whole grain products, mostly in their peels and husks (bran).
The human microbiota prefers dietary fiber. However, if there is not enough fiber available when your food reaches the large intestine, the microbiota will turn to protein fermentation. Why do we want to avoid that? Instead of the beneficial fermentation products, co-carcinogenic and mutagenic end-products are formed. This is another reason why one shouldn't overconsume protein without eating some veggies.
On average, it is recommended to consume at least 25-35 g of dietary fiber per day. We'll look more into how to consume enough in practice in one of the next articles!
Did you know that you can change the dietary fiber content in potatoes and grains depending on how you prepare them?
Did you know that you can change the dietary fiber content in potatoes and grains depending on how you prepare them?
You can increase the fiber content by boiling the grains or potatoes, letting them rest and cool down completely, or using them in further cooking later. Why? During cooking, due to the increased temperature and water availability, the starch in the potatoes and grains gelatinizes. If you cool a gelatinized starch, part of it becomes resistant starch, which is a dietary fiber since it cannot be digested by human enzymes anymore.
Of course, this is not a standard practice for everyday cooking. However, it's good to know that having leftover grains and potatoes can have some additional value and that you can sometimes get more fiber this way.
If you haven't tried boiled and then oven-baked potatoes, you definitely should! Smash them just a little with a potato masher after boiling, and you'll get some really delicious potatoes with a crisp outside yet soft, flaky core after cooking, with more fiber as a bonus!
P.S. Don't forget that whole grains and potatoes with skin have more dietary fiber than refined grains and peeled potatoes.
Last updated: 10/7/2024
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