Fiber Facts and Fictions Brought to Life

by ProfKeith

I remember an English comedian (Jasper Carrot) talking about Audrey Eyton’s “F-Plan Diet”, back in the 1980s. Beans for breakfast, beans for lunch, beans for supper, beans with everything… No wonder it’s called the F-Plan, he quipped! (farting, get it?)

I used to joke that if fiber facts was all it took, we’d just need to chop up the carpets and eat those and we’d all be healthy. I thought there must be more to it than that… And so there is.

If you are confused by it all, you won’t be after reading this. Dietary fiber has been a much misunderstood nutrient. Many people know it is important, but not much more than that. It’s time to straighten it all out and make it nice and simple.

What Is Dietary Fiber?

Dietary fiber, also known as roughage or bulk, includes all parts of plant foods that your body can’t digest or absorb. Unlike other food components, such as fats, proteins or carbohydrates, fiber isn’t digested by your body. Instead, it passes relatively intact through your stomach, small intestine, colon and out of the other end.

Fiber helps to maintain a solid formed stool, instead of just sludge from your back passage or—even worse—concreted, hard rocks that you can pass only with extreme difficulty.

So it’s a part of the process of stool formation but not involved in the carbs, proteins and fats digestion story. Actually, my joke about eating carpets comes close to how you need to picture this.

So what? You might ask. Well, actually fiber is important in many ways, we have discovered over the years.

It helps with weight loss, lowers cholesterol, prevents heart disease, lessens the risk of cancer and diabetes, improves digestion and greatly benefits our gut flora, for a start.

Pay attention, this is important!

Soluble vs. Insoluble Fiber

fiber factsThere are two main types of fiber: soluble and insoluble. Soluble fiber dissolves in water; insoluble fiber does not. Both are beneficial for health but each in different ways.

Soluble fiber attracts water and forms a gel, which slows down digestion. Soluble fiber delays the emptying of your stomach and makes you feel full, which helps control weight. Slower stomach emptying may also affect blood sugar levels and have a beneficial effect on insulin sensitivity, which may help control diabetes. Soluble fibers can also help lower LDL (“bad”) blood cholesterol by interfering with the absorption of dietary cholesterol.

Sources of soluble fiber:

  • Oatmeal
  • Oat cereal
  • Lentils
  • Apples
  • Oranges
  • Pears
  • Oat bran
  • Strawberries
  • Nuts
  • Flaxseeds
  • Beans
  • Dried peas
  • Blueberries
  • Psyllium
  • Cucumbers
  • Celery
  • Carrots

Insoluble fibers are considered gut-healthy fiber because they have a laxative effect and add bulk to the diet, helping prevent constipation. These fibers do not dissolve in water, so they pass through the gastrointestinal tract relatively intact, and speed up the passage of food and waste through your gut.

Sources of insoluble fiber:

  • Whole wheat
  • Whole grains
  • Wheat bran
  • Corn bran
  • Seeds
  • Nuts
  • Barley
  • Couscous
  • Brown rice
  • Bulgur
  • Zucchini
  • Celery
  • Broccoli
  • Cabbage
  • Onions
  • Tomatoes
  • Carrots
  • Cucumbers
  • Green beans
  • Dark leafy vegetables
  • Raisins & grapes
  • Fruit
  • Root vegetable skins

Some plants contain significant amounts of both soluble and insoluble fiber. For example plums and prunes have insoluble fiber in the skin and soluble fiber in the pulp.

Synthetic Fiber Facts Products

You probably know about psyllium husks, loved by doctors because it is a “real” drug and prescribable! They like Inulin too, because it’s “real” (see below).

There are some other odd products on the market, such as glucomannan, an extract of the konjac plant (also known as konjaku, konnyaku, or the konnyaku potato). It is a water-soluble mixture of glucose and mannose and is considered a fiber facts product.

Japanese shirataki noodles (also marketed as “miracle noodles”) are made from glucomannan. You can put these gooey noodles with anything and assume them to be zero calories. They lack flavor though.

In one 2007 study of glucomannan, published in the British Journal of Nutrition [Br J Nutr. 2008 Jun;99(6):1380-7. Epub 2007 Nov 22.], participants taking a glucomannan and psyllium husk combination supplement lost approximately 10 pounds in 16 weeks compared to 1.7 pounds lost in the placebo group. Another study using only glucomannan showed an average of 5.5 pounds lost over eight weeks, without making any other diet or lifestyle changes [Int J Obes. 1984;8(4):289-93].

Vegetable gum fiber supplements are also relatively new to the market. Often sold as a powder, vegetable gum fibers dissolve easily with no aftertaste. In preliminary clinical trials, they have proven effective for the treatment of irritable bowel syndrome.

[Dig Dis Sci. 47 (8): 1697–704]

Examples of vegetable gum fibers are guar gum and acacia Senegal gum.

How Much?

We need about 30 – 40 grams a day; women somewhat less than men and we all need less as we grow older. Most Westerners get 20 grams or less: not enough.

But don’t suddenly up your intake, otherwise you will be blowing off (breaking wind) and upsetting those around you. Increase your intake slowly towards the optimum and take plenty of water at the same time; soluble fiber needs that and despite what you have read, it isn’t easy to pass soluble fiber, if water is short. It will swell and tend to block the intestine, which is the opposite of what is wanted.

As I said, most plants contain both soluble and insoluble fiber. However, the amount of each type varies in different plant foods. If you focus on eating a healthy diet rich in fruits, vegetables, whole grains, legumes, nuts, and seeds, you will certainly take in plenty of fiber.

Remember, animals, fowl and fish foods contain no worthwhile fiber.

Weight Loss Benefits

One of the great things about eating fiber is it gives that pleasant full feeling, without actually adding to your calories. High-fiber foods generally require more chewing, which gives your body time to register when you’re no longer hungry, so you’re less likely to overeat.

In conjunction with leaving you feeling more satisfied, fiber helps properly regulate our weight-control hormones, such as insulin, ghrelin and leptin. Fiber facts foods can slow the absorption of sugar and help improve blood sugar levels. So a healthy diet that includes fiber may reduce the risk of developing type 2 diabetes.

Slimmer’s need to understand the importance of fiber foods and choose carefully from among them. Fruits and veggies enjoy no great reputation but plant foods are essential for the fiber ingredient they bring.

Pre-Biotics vs. Probiotic

Now we come to the real reason that fiber is important to health. I believe this part of the story is much more relevant than just the idea of chopped up carpets! Fiber is a pre-biotic.

Definition: a pre-biotic is a non-digestible food ingredient that stimulates the healthy growth and/or activity of bacteria in the digestive system in ways beneficial to overall health. The term (and concept) was coined by Marcel Roberfroid in 1995.[ J Nutr. 125 (6): 1401–1412]

The prebiotic definition does not emphasize a specific bacterial group. Generally, however, it is assumed that a prebiotic should increase the number and/or activity of bifidobacteria and lactic acid bacteria. The importance of the bifidobacteria and the lactic acid bacteria (LABs) is that these groups of bacteria may have several beneficial effects on the host, especially in terms of improving digestion (including enhancing mineral absorption[J Nutr. 137 (11 Suppl): 2527S–2533S]) and the effectiveness and intrinsic strength of the immune system.[ J Nutr. 137 (11 Suppl): 2563S–2567S]

Both types of fiber benefit healthy bowel flora but more so the soluble type.
Traditional dietary sources of pre-biotics include soybeans, inulin sources (such as Jerusalem artichoke, jicama, and chicory root), raw oats, unrefined (whole) wheat, unrefined barley, and yacon.

It is interesting to note that the ONLY non-plant source of suitable pre-biotic oligosaccharides is human breast milk and these are believed to play an important role in the development of a healthy immune system in infants.
[Jackson, Frank. “Breast Milk”. Jackson GI Medical http://www.prebiotin.com/breast-milk/ Retrieved 16 June 2013]

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