By Curtis Sheppard
With changing dietary fashions, the current emphasis on low-fat items – witness the vast array of ‘light’ and fat-reduced products lining supermarket shelves – has given dietary fibre a back seat. Although people may pay less attention to fibre, its health benefits have not vanished. Fibre remains an essential nutrient and a vital part of healthy eating for everyone, including those with diabetes. In fact, soluble forms of plant fibre may help to mute blood sugar swings.
High Fibre Foods
Under the less trendy term ‘roughage,’ fibre enjoyed great respect among our grandparents, and during the 1970s its image was resurrected by British physician Dennis Burkett, who practised for many years in rural Africa. He attributed the rarity of ailments such as hernias, hemorrhoids, diabetes, diverticulitis (small outpunchings of the large intestine), heart disease and bowel disease in that area to native diets rich in whole grains, seeds, roots, vegetables and nuts. He blamed the high incidence of these disorders in Western countries on a lack of dietary fibre. Burkett’s theories were enthusiastically adopted in the 1970s as the ‘Bran Hypothesis’.
Many of us may remember the heyday of bran during the late 1970s and early 1980s with massive promotion of bran cereals and granola. Next came the oat bran craze, with oat products in all shapes and sizes flooding the market claiming to lower blood cholesterol and fight heart disease. A 1990’s review of many studies examining the link between oats and health concluded that at best, oat cereals may modestly reduce blood cholesterol.
However, after a lull, oat cereals are again making headlines as the American Food and Drug Administration has permitted product labels to carry health claims that oatmeal and oat cereals may reduce the risk of heart disease – as part of a diet low in fat and cholesterol. Although oat bran may be back, most dietary experts caution that no one fibre is better than others. Neither oats nor wheat bran are the whole story. ‘A spoonful of oats (or bran) a day’ is no cure for many disorders. Most scientists agree that different types of fibre confer different health benefits for everyone, including seniors.
What Exactly is Fibre?
Traditionally, fibre was considered to be an inert part of food, passing undigested from mouth to anus and expelled intact in the stool. This view has been revised and the term ‘fibre’ now encompasses complex carbohydrates and natural polymers such as cellulose and woody plant lignin, as well as pectin and various gums (guar, arabic, agar, carageen) and psyllium, and many others not yet identified. Far from being inert, different fibres exert different bodily effects. Fibre is often divided into two broad classes: insoluble and soluble forms. Wheat bran, for instance, is an insoluble form that is a good stool-softener but a poor absorber of cholesterol, a function that the soluble form, oat bran, does better.
Insoluble fibre makes stools heavier and speeds their passage through the gut. Like a sponge, it absorbs many times its weight in water, swelling up and helping to eliminate feces and relieve constipation. Wheat bran and whole grains, as well as the skins of many fruits and vegetables, and seeds, are rich sources of insoluble fibre. High-fibre diets have replaced bland, low-residue treatments for bowel problems such as diverticular disease.
Also note that as the outer fibre layer is often removed in food processing by milling, peeling, boiling or extracting, it’s wise to eat more unrefined foods to obtain insoluble fibre.
Soluble fibre includes pectin, gums (such as guar), betaglucans, some hemicellulose and other compounds and is found in oats, legumes (peas, kidney beans, lentils), some seeds, brown rice, barley, oats, fruits (such as apples), some green vegetables (such as broccoli) and potatoes. Soluble fibre breaks down as it passes though the digestive tract, forming a gel that traps some substances related to high cholesterol. There is some evidence that soluble fibre may lessen heart disease risks by reducing the absorption of cholesterol into the bloodstream. Studies find that people on high-fibre diets have lower total cholesterol levels and may be less likely to form harmful blood clots than those who consume less soluble fibre. A recent USA report found that, in sufficient amounts, fibre apparently reduced heart disease risks among men who ate more than 25 grams per day, compared to those consuming under 15 grams daily.
Benefit for Those with Diabetes
Soluble fibre in oat bran, legumes (dried beans of all kinds, peas and lentils), and pectin (from fruit, such as apples) and forms in root vegetables (such as carrots) is considered especially helpful for people with either form of diabetes. Soluble fibre may help control blood sugar by delaying gastric (stomach) emptying, retarding the entry of glucose into the bloodstream and lessening the postprandial (post-meal) rise in blood sugar. It may lessen insulin requirements in those with type 1 diabetes. Because fibre slows the digestion of foods, it can help blunt the sudden spikes in blood glucose that may occur after a low-fibre meal. Such blood sugar peaks stimulate the pancreas to pump out more insulin. Some researchers believe that a lifetime of blood glucose spikes could contribute to type 2 diabetes, which typically strikes after the age of 40, and more than doubles the risk of stroke and heart disease. The cholesterol-lowering effect of soluble fibres may also help those with diabetes by reducing heart disease risks.
How Much Fibre?
According to current Canadian guidelines, healthy adults should consume at least 26 grams of fibre – ideally 26 to 35 grams daily*. The present Canadian fibre intake only averages 4.5 to 11 grams a day. Health Canada suggests increasing this amount by eating more grains and unpeeled (but well-washed) fruit and vegetables. Be sure to include both insoluble fibre and soluble types.
Another plus of a fibre-rich diet is that it provides plenty of vitamins and minerals, but it may be wise to consult a physician before greatly increasing dietary fibre intake and to ensure good nutritional status before making drastic alterations. Initially, eating large quantities of fibre may cause bloating, but this should subside in a few weeks. It is best to increase amounts gradually. Eating 26 grams of fibre daily may seem like a lot but can be obtained by having two fruits at breakfast-time (say a banana and raisins) with whole grain cereal, fruit as between-meal snacks, three to five servings of vegetables daily, and several bread and grain servings.
Note, however, that people with diabetes should watch their fruit intake.
* People with diabetes should have 25 to 50 grams per day.
The Benefits of Eating Fibre
- Combats constipation
- The most undisputed advantage of insoluble fibre is its ability to soften and expand stool volume, speeding up fecal transit and elimination.
- Commercial preparations such as agar (Agarol) and psyllium (Metamucil) are effective stool bulkers.
- Soluble fibre from legumes, barley, oats, some fruit and vegetables can help regulate blood sugar swings and by lowering serum cholesterol, protect against heart disease.
- Excess blood fats are possibly reduced by soluble fibres such as pectin, bean and oat gums, and the types in legumes (lentils, chickpeas, navy, pinto or kidney beans).
- May improve by diets rich in fibre, through its cholesterol lowering effects.
Possible protection against cancer
- In the bowel, bacteria converts fibre into short chain fatty acids, which provide energy for the body and may help protect against cancer.