Finding your fibre (roughage and aging)
Christopher Thomas
Some elements in our diet are indigestible. But that does not mean that they are useless. In fact, our bodies make use of most things we eat, even if we don’t digest them. One example of this is dietary fibre.
Fibre is only found in plants. It is the indigestible part of plant material (also known as ‘roughage’). There are two types of dietary fibre: those that dissolve in water (soluble fibre) and those that do not (insoluble fibre). Most plants contain a mixture of the two (at a ratio of about 3:1 insoluble to soluble) and both forms are vitally important in our diet.
Good sources of fibre
Insoluble fibre (such as cellulose and lignin) is found in whole grains, particularly in the outer husk or bran (e.g. oat bran, wheat bran, rice bran). Milling or refining removes the bran and therefore much of the fibre. For example, wheat flour made from whole grains contains 10 times the fibre as standard white flour. Lower levels of insoluble fibre are also found in nuts, seeds and refined cereals such as flour. Lignin is also found in the skin of fruit and vegetables, such as strawberries, prunes, tomatoes, potatoes and onions.
Soluble fibre (such as gums, beta-glucans, psyllium, mucilages and pectins) is found in most plant foods, with the highest amounts in oats, bran, barley, legumes, nuts, soy products and some yeasts. Fruit and vegetables also contain significant levels of fibre. Fruits high in fibre include plums, Asian pears, raspberries, blackberries, apples and citrus pulp. Nonlegume vegetables high in fibre include cauliflower, zucchini, broccoli, carrots, Jerusalem artichokes and celery. However, these fibre levels are still lower than in legumes.
Diets that are naturally high in fibre have a number of positive effects on our health to:
- Improve blood sugar levels – soluble fibre slows the absorption of glucose from the foods we eat, which creates a sustained energy release and lowers the strain on insulin production.
- Reduce bad (LDL) cholesterol levels – about a 10% reduction is seen with psyllium supplements.
- Improve weight management — consuming fibre-rich foods can make us feel satisfied sooner and feel full for longer (and therefore less likely to feel hungry or snack between meals). Soluble fibre can also reduce the absorption of nutrients (including sugars, fats and proteins), meaning their energy is lost to our metabolism (to the gain of our healthy gut bacteria). Even the extra chewing time of high fibre foods helps slow the intake of food and reduce the amount (of calories) we consume.
- Reduce the risk of heart attack — significant cardiovascular benefits are seen in diets rich in insoluble fibre beyond lowering cholesterol. For example, lignins like sesamin and sesamolin from sesame seed have beneficial effects on the immune system and can reduce oxidative stress. The bran and germ of whole grains are also rich in minerals, vitamins, antioxidants and other phytochemicals that have positive effects on heart disease.
- Improves bowel health – insoluble fibre makes the stool more soft and bulky, allowing it to move more easily through the intestine and colon. This is useful for the prevention and management of constipation.
- Helps the work of our gut bacteria – dietary fibre is fermented by the gut bacteria of the large intestine. This process releases gas, as well as a number of beneficial compounds like short-chain fatty acids. These help the absorption of minerals and contribute to lower rates of bowel cancer for those on a high fibre diet.
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Tags: antioxidants; oxidative damage, disease, elements of aging, stress, supplements, Weight management
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