The Mediterranean diet has been identified by many studies as a healthy one for all ages. The diet is high in fibre, and many of its health benefits have been linked to the fibre-rich foods. What adds value is that fibre is found in many naturally occurring foods.
It is good to understand what different forms of carbohydrates exist and what fibre is. Simple carbohydrates consist of one or two units of sugar, or saccharide, while complex carbohydrates contain three or more sugars linked together.
Polysaccharides have at least 10 sugars and may have many thousands of sugar molecules combined. Starches are polysaccharides. They are digestible because we have enzymes which break the bonds between each sugar molecule in starches.
For fibre (also called non-starch polysaccharides and non-digestable polysaccharides), the human body doesn’t have the enzymes required to cleave the type of bond holding the molecules together, so they’re not digested, and pass through the stomach and small intestine intact.
Fibre is commonly classified as soluble, which dissolves in water, or insoluble, which doesn’t dissolve. Soluble fibre dissolves in water to form a gel-like material and can help lower blood cholesterol and glucose levels. Insoluble fibre promotes the movement of material through our digestive system and increases stool bulk, so it can be of benefit to those who struggle with constipation or irregular stools.
Denis Burkitt was the first researcher to connect a high-fibre diet with better health. Studying rural communities in Africa, he noticed that eating their traditional high-fibre diet resulted in healthier stools and bowel movements in contrast to those living in cities and consuming a western diet.
He further saw that those eating local produce suffered less from conditions such as diabetes, irritable bowel syndrome, constipation, diverticular disease, colon cancer or heart disease compared with those who were eating a western diet. After looking at many factors, Dr Burkitt concluded that the high amount of fibre in traditional diets was necessary for maintaining good health.
Further research has been done in this area and more evidence shows the health benefit of high-fibre products from unrefined plant foods such as wholegrain cereals, vegetables, fruits and legumes. According to major public health bodies, the health effects of dietary fibre span from gastrointestinal health to risk reduction of several common non-communicable diseases such as cardiovascular diseases, type 2 diabetes, colorectal cancer and obesity.
An analysis of many studies showed that consumption of cereal fibre was associated with an 18 per cent lower risk of cardiovascular disease (heart disease and stroke) mortality. Soluble fibre found in beans, oats, flaxseed and oat bran may also help lower total blood cholesterol levels by lowering low-density lipoprotein.
As you increase your fibre intake it is important to increase your fluids as well
Studies have also shown that high-fibre foods may have other heart-health benefits, such as reducing blood pressure and inflammation. Fibre can slow the absorption of sugar and help improve blood sugar levels in people with diabetes.
High-fibre foods have a role in weight management. These are more filling than low-fibre foods and tend to take longer to eat and to be less ‘energy dense’. So it’s a question of fewer calories for the same volume of food.
A compilation of studies has indicated a 10 per cent reduction in risk of colorectal cancer for each 10g/day intake of total dietary fibre and cereal fibre and about a 20 per cent reduction for each three servings (90g/day) of wholegrain daily, and further reductions with higher intake. This meta-analysis suggests that a high intake of dietary fibre, particularly from cereal and wholegrains, is associated with a reduced risk of colorectal cancer.
Main dietary sources of fibre are foods of plant origin such as legumes, wholegrain cereals, fruit, vegetables, nuts and seeds. There are various forms of fibre, including cellulose, pectin, hemicelluloses and beta-glucan. Vegetables are one of the best sources of cellulose. Those with the highest amounts include broccoli, carrots, brussels sprouts and green peas.
In fact, cellulose accounts for a third of their total fibre. Fruits are the best known sources of pectin, with apples, oranges and grapefruit topping the list. Fruits, vegetables, legumes and nuts also provide hemicelluloses. Oats are good sources of beta-glucan.
In adults, the recommended amounts of dietary fibre for the prevention of non-communicable diseases, such as diabetes type 2, colorectal cancer, CVD and risk factors such as overweight and obesity range from 25 to 38g/day. In children, recommended amounts vary according to the energy requirements of different age groups.
To increase your fibre intake you could:
• Choose a high-fibre breakfast cereal e.g. oats;
• Go for wholemeal or granary breads instead of white bread;
• Choose wholegrains like wholewheat pasta, bulghur wheat or brown rice;
• Go for potatoes with skins e.g. baked potato or boiled new potatoes;
• For snacks try fruit, vegetable sticks, rye crackers, oatcakes, unsalted nuts or seeds;
• Include plenty of vegetables with meals – either as a side dish or added to sauces, stews or curries;
• Add pulses like beans, lentils, peas or chickpeas to soups, stews, curries and salads. You can also puree them into a dip or spread;
• Add fresh fruits to cereal, as a snack, or as a simple dessert;
• Increase the fibre content of your own baked goods by using wholewheat flour in place of all-purpose white flour in recipes, adding oatmeal and fruits to bakes;
• As you increase your fibre intake it is important to increase your fluids as well. Fibre pulls water into the intestines. Without adequate hydration, fibre can aggravate rather than alleviate constipation. So it is important to drink at least eight glasses of water a day.
It is important to consume different types of food for an overall balanced diet. This will help you enjoy food and gain all the benefits for health.
Prof. Charmaine Gauci is Superintendent of Public Health.