A lot of individuals wonder what fibers actually are and why they could be beneficial to them and what whole grains are. I will try to answer these questions in this post.
Dietary fibers are nondigestible carbohydrates (due to the fact that they are resistant to hydrolysis, which is a chemical process where molecules are split into two parts through added water). Dietary fibers are therefore carbohydrates that we, humans, can not digest in contrast to ruminants, such as the cow, and we can therefore not extract energy from it… Except for one little fact which I will write about below.
Dietary fibers are often divided into subgroups. Such as fermentable fibers, non fermentable fibers, (water) soluble fibers, (water) insoluble fibers, gel forming fibers and non gel forming fibers. All these different group of fibers come with slightly different benefits.
Bacteria in our intestines ferment (splint through an anaerobic process) a particular subgroup of dietary fibers, the fermentable dietary fibers into different substances, such as carbon dioxide, hydrogen gas, hydrogen sulphide, methane, but also short chains of fatty acids such as acetate, propionic acid and butyrate. These fatty acids have some positive effects just like all other dietary fibers, but acetate in particular is the one fatty acid that is most commonly produced and is the only acid which grants us energy, because it reaches the blood circulation. Propionic acid is known to reduce the cholesterol production. Butyrate is the foremost energy source for the intestinal cells, and therefore it stimulates its growth, but it also aid in apoptosis – cell death of cancer cells.
In short: We eat fermentable fibers, bacterias in our intestines splint them into acetate which we can use as an energy source. This is where 2 kilocalories of (fermentable) dietary fibers per gram comes from. 1 gram of fermentable fibers equals 2 kilocalories, or approximately 8.36 kilojoule.
Dietary fibers can be found in pretty much all foods from the vegetable- and plant kingdom – Vegetables, fruits, leguminous plants, grains (particularly whole grains), nuts and so on.
The US Department of Agriculture (USDA), US Department of Health and Human Services recommended, in 2005, a daily intake of 28 g for the average adult women and 35 g for adult men depending on daily caloric intake. In Sweden the recommmendation is 25-35 grams per day, pretty much the same.
Dietary fibers, or roughage as it can be called, have a great many benefits. Here are a few:
- Reduce cholesterol production
- Some grant energy (through acetate)
- Lowers the glycemic index (GI)
- Lowers the pH-value
- Bind water (Bulk effect)
- Increase intestine volume (Bulk effect)
- Reduced risk of constipation (Bulk effect)
- Reduced risk of diarrhea
- Reduced risk of cancer, particularly colon cancer
- Increase saturation (aid in weight loss)
- Ease the mineral absorption
- Ease the electrolyte (different ions) absorption
- Slows down the gastric emptying
- Ease the water absorption (drink water if you have increased your fiber intake!)
- Reduced risk of obesity/overweight
- Reduced risk of heart attack
- Reduced risk of diabetes
- Reduced risk of mental illnesses through avoidance of several diseases (obesity etc)
- Reduced risk of stroke
- Increases health and function of gastrointestinal system
- Increases the immune system’s health
- Keeping the blood sugar levels steady
- Reduced risk of dental caries
- Protection against unhealthy substances in our intestines
- Reduced risk of kidney stones
- Reduced risk of skin breakouts and rashes
Now some bad news, according to a study released in 2009, the average fiber intake for adults and children in the US are less than half of the recommendations. Eat more fibers! Especially considered all the above benefits.
One last thing I would like to write about is whole grain. I have been asked what the difference between whole grain and dietary fibers are. And the difference is pretty big but still understandably slight.
Now, whole grains are nothing but grains whom still have the endosperm, bran (most fibre-rich) and germ intact. The husk, or shell is pretty much complete. These whole grains often contain high amount of fibers. So, whole grains contain, amongst other things, fibers, and fibers are where all the benefits come from.