Are you eating enough fibre every day?

Morning in Maui (Dr. Noorali Bharwani)
Morning in Maui (Dr. Noorali Bharwani)

Last time I wrote about this subject was on April 6, 2010 (Fibre, Flatulence and Weight Loss Diet). It is about time we review the subject. Recently, the Lancet medical journal (January 10, 2019) published an article titled “Carbohydrate quality and human health: a series of systematic reviews and meta-analyses”.

After analysing 185 studies and 58 clinical trials, the results are in and have been published in the Lancet medical journal.

“The evidence is now overwhelming and this is a game-changer that people have to start doing something about it,” says one of the researchers involved in the Lancet article, Prof John Cummings, speaking to BBC News.

There used to be a view that fibre didn’t do much at all – that the human body could not digest it and it just sailed through.

But fibre makes us feel full and affects the way fat is absorbed in the small intestine – and things really become interesting in the large intestines, when your gut bacteria get to have their dinner. The large intestine is home to billions of bacteria – and fibre is their food.

“We have this organ (colon) set up to digest fibre, which a lot of people just don’t use very much,” says Prof Cummings.

Dietary fibre is well known for stopping constipation – but its health benefits are much broader than that. Only about 10 per cent of the population eat adequate amount of fibre.

Health Canada says Canadian women need 25 grams of fibre per day and men need 38 grams of fibre per day. On average, women consume about 17g and men 21g a day. We need to increase that. Fibre is cheap and widely available in the supermarket.

Fibre is a non-digestible carbohydrate found in plant foods. It is an important part of a healthy diet and plays many roles in the body. Fibre helps bowel move regularly, lower blood cholesterol levels, makes you feel full longer and helps you lose weight.

Is it difficult to find dietary fibre in the market?

Not really. Dietary fibre is found in fruits, legumes such as dried beans, lentils, peas, and soybeans. The list does not end there. Nuts, seeds, vegetables, whole grains such as whole grain breads, cereals, crackers and pasta, brown rice, barley and oats, are available in all grocery stores.

The more fibre you eat, the more gas you produce. There is not much you can do about it except look over your shoulder and let it out. Is that embarrassing? May be. Look at the advantages. You avoid constipation. Constipation leads to hemorrhoids, lazy bowel, irritable bowel syndrome and anal fissures. What would you prefer?

Dietary fibre has been shown to lower LDL (bad cholesterol), reduces the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces by-products which are healthy for you. Regular bowels may prevent colon cancer and diverticulosis. More important, it makes you feel better.

Finally, you should avoid dietary regimes that recommend very low-carbohydrate diets. A low-carb diet limits carbohydrate like grains, fruits, vegetables, milk, nuts, seeds and legumes (beans, lentils, peas) and emphasizes foods high in protein and fat.

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Fibre, Flatulence and Weight Loss Diet

“Eat your porridge – it is good for you”

“Eat your fruits and vegetables – they are good for you.”

This is a common mantra given to people who want to eat a well balanced healthy diet. But, how often do we ask, “What does this really mean? Is there any science behind it or is it all hot air at the end of the tunnel?” You know what I mean.

Dietary fibre is found in plants. Fibre is composed of cellulose (a complex carbohydrate that is composed of glucose units, forms the main constituent of the cell wall in most plants), lignin (chief non-carbohydrate constituent of wood), pentosans (group of polysaccharides found with cellulose in many woody plants), pectin (water-soluble carbohydrate found in ripe fruits) and gums (viscid exudation from plants).

Fibre is divided into soluble and insoluble fibre.

Soluble fibre dissolves in water to form a gel-like substance. It is readily fermented by bacteria in the colon into gases and physiologically active byproducts. Sources of soluble fibre are oats, legumes (beans, peas, and soybeans), apples, bananas, berries, barley, some vegetables, and psyllium. More fibre you eat, more gas you produce. There is not much you can do about it except look over your shoulder and let it out.

Soluble fibre has now been shown to lower LDL (bad cholesterol) levels through a series of processes that alter cholesterol and glucose metabolism – reduces the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces byproducts with wide-ranging physiological activities.

Insoluble fibre increases the movement of material through the digestive tract and increases stool bulk by absorbing water and easing defaecation, reduces transit time, thus preventing constipation which decreases the opportunity for both nutrients and fecal mutagens to interact with the intestinal lining. There is no fermentation by bacteria. Sources of insoluble fibre are whole wheat foods, bran, nuts, seeds and the skin of some fruits and vegetables.

Constipation leads to hemorrhoids and anal fissures. Although insoluble fibre is associated with reduced diabetes risk, the mechanism by which this occurs is unknown. Although many researchers believe that dietary fibre intake reduces risk of colon cancer, one study conducted by researchers at the Harvard School of Medicine of over 88,000 women did not show a statistically significant relationship between higher fibre consumption and lower rates of colorectal cancer or adenomas.

The five most fibre-rich plant foods, according to the Micronutrient Center of the Linus Pauling Institute, are legumes (15–19 grams of fibre per US cup serving, including several types of beans, lentils, and peas), bran (17 grams per cup), prunes (12 grams), Asian pear (10 grams each, 3.6% by weight), and quinoa (9 grams).

On average, North Americans consume less than 50 per cent of the dietary fibre levels required for good health. Current recommendations from the United States National Academy of Sciences, Institute of Medicine, suggest that adults should consume 20–35 grams of dietary fibre per day.

Although fibre falls under the category of carbohydrates, it is low in calories. Regardless of the type of fibre, the body absorbs fewer than 4 Calories (16.7 kilojoules) per gram of fibre. In some countries, fibre is not listed on nutrition labels, and is considered 0 Calories/gram when the food’s total Calories are computed.

For weight loss, a diet rich in fibre from cereals, not from fruit and vegetables, is more likely to help limit weight gain, says Dr. Khursheed Jeejeebhoy, a well known gastroenterologist in Toronto, writing in the Medical Post (March 9, 2010). High-fibre breakfast reduces subsequent intake of energy, delays digestion and slows absorption. A Dutch study found that an intake of 10 g of total fibre per day was associated with a loss of 39 g of body weight per year and a reduction in waist circumference of 0.08 cm per year.

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Are you constipated?

Chronic constipation is a very common problem. I see patients with stomach and bowel problems all the time and constipation is high on their list of complaints. Usually, it has been present for many years. We usually tell patients with chronic constipation to take high fiber diet, do regular exercise and drink plenty of fluids. But what really works for constipation?

Let us start by defining what chronic constipation is. Unfortunately, there is no simple definition. Most people complain of constipation if they do not have a bowel movement for a few days or if they have difficulty emptying. Generally speaking, constipation is defined as having a bowel movement fewer than three times a week. The bowel movements are usually hard, dry, and small in size.

We do not need a daily bowel movement to be healthy. We do not have to spend money on bowel cleansing with laxatives and enemas to get rid of so called toxins. Daily bowel movements are not important for overall health.

As part of my research for this column, I came across an article in the American Journal of Medicine (AJM) titled: Constipation in the Primary Care Setting: Current Concepts and Misconceptions. The article reviews what works and what does not work in patients with chronic constipation. Here are some important points discussed in the article.

Regular exercise, high fiber diet and fluids are good choices for a healthy life style. But if one of these choices is missing in your life then it would not be a major factor in causing chronic constipation.

High fiber diet increases stool weight and frequency in healthy individuals and decreases the time it takes for the stool to travel to the rectum. Increase intake of fiber has shown to help some chronically constipated individuals. High fiber diet does not help patients who have irritable bowel syndrome where constipation is the dominant symptom, patients who have slow large bowel transit time or have problem with emptying the rectum due to muscle weakness. That means all constipated patients will not benefit from high fiber diet.

What about fluid intake and exercise? The article says that adequate fluid intake and regular exercise improves general health but there is no evidence to support the use of these measures in treating constipation

What about the laxatives? Laxatives are among the most widely used medications in Western countries, says the AJM article. Laxatives are designed to increase the frequency and ease of bowel movement. They are easily accessible and sometimes abused as most of them can be purchased over-the-counter. There are three categories of laxatives:
-Bulk agents: psyllium, methylcellulose, Calcium polycarbophil
-Osmotic agents: polyethylene glycol, lactulose, sorbitol, glycerine suppositories magnesium citrate, magnesium sulfate
-Bowel stimulants: bisacodyl, senna

Bulk agents like psyllium work in similar fashion to high fiber diet. Studies have shown that osmotic laxatives like lactulose, sorbitol and polyethylene glycol are effective. Stimulant laxatives are also effective in many patients with constipation, although certainly not all. Except for bloating and flatulence, laxatives have few side effects. Once daily dosage should be encouraged for better compliance. There is no evidence to support the belief that stimulant laxatives like senna can damage colonic nerves if chronically used.

The article says that although tolerance to laxatives has not been studied extensively in humans, it seems to be uncommon in the majority of laxative users. Tolerance to stimulant laxatives occurs in patients who have constipation due to slow transit time and whose colons have poor neurological function. Can you get addicted, habituated or dependent on laxatives? The answer is no. Most laxatives are not absorbed in the system so there is no risk of addiction.

So, high fiber diet, adequate fluid intake, regular exercise and psyllium should work for most patients with chronic constipation. If you are resistant to these measures then you can add something like lactulose or a stool softener. If that does not work then add senna.

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Constipation and Laxatives

Constipation continues to be a problem for up to 30 percent of the population.

This is not something new. Even during the time of Hippocrates, people were worried about their bowel movements. It was recognized then that eating unrefined foods gave better bowel movements and better health.

Dictionary defines constipation as difficult, incomplete, or infrequent evacuation of dry hardened feces from the bowels. For some it means straining to have a bowel movement, to others a process of passing hard stools, or infrequent passage of stools, or inability to defecate at will.

A study of healthy people in Great Britain found that 99 percent of the population had between three bowel movements a week and three bowel movements a day.

Constipation is associated with (not necessarily caused by) inactivity, low calorie intake, number of medications being taken, low income, and a low education level. Constipation is also associated with depression as well as physical and sexual abuse, says an article in Gastroenterology.

Constipation can be due to slow transit of low quantity of stool which fails to stimulate the colon to move in orderly fashion. There may also be uncoordinated movement of the colon near the rectum or dysfunctional pelvic floor which causes pseudo-obstruction.

The Gastroenterology article says that about 60 percent of patients with constipation have irritable bowel syndrome with normal colonic transit time (or slightly delayed only). About 30 percent have pelvic floor dysfunction (with or without slow transit), and 10 percent has slow transit only.

Management of constipation starts with history and physical examination, review of patient’s current medications, basic blood work and investigation of the colon to rule out bowel blockage.

If everything is normal then constipation may be easily corrected by increasing dietary fiber (bran, cereal, fresh fruit, and vegetables), intake of liquids and increasing physical activity.

If this fails then use of laxatives (agents which promote evacuation of the bowel) become necessary. Commonly used laxatives are described here briefly.

Bulk forming agents (psyllium, methylcellulose) are considered the safest. They work like a sponge – they soften stool by holding water in the fecal matter.

Stool softeners (docussate sodium) soften faces by lowering the surface tension of fluids in the bowel which seems to allow more water to remain in the stool.

Stimulants (senna, bisacodyl, cascara, castor oil) act by increasing the colonic muscle contractions. Long term use of these agents is discouraged because of the theoretical risk of damaging the nerve centers in the colon.

Lubricants like mineral oil (liquid paraffin) is chemically inert and not digested in the gut. It probably acts by lubricating the bowel. It may interfere with absorption of fat soluble vitamins such as A, D and K. Sometimes aspiration of liquid paraffin may cause pneumonia.

Lactulose is a synthetic disaccharide. It is not absorbed in the gut. Its mode of action as a laxative is not clear.

Magnesium and phosphate containing agents are considered saline laxatives. They work by drawing water into the large bowel. They should be used with care in patients with kidney and heart problems.

This is only a short list of common laxatives. There are numerous other off the counter laxatives which are used and abused by the general public. For most patients proper use of laxatives is all that is required. For a small minority, our options should go beyond laxatives and include behavioral treatment as well as new drugs.

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