New Zealanders do not eat enough dietary fibre. Adult men and women are consuming approximately a third less than the recommended daily intakes (Dietary Fibre 2015).
What’s so important about this nutrient?
What is dietary fibre?
This term originated in the 1950s to describe the non-digestible parts of the plant cell wall. A more modern and precise definition states dietary fibre is made up of carbohydrate polymers that are not digested nor absorbed in the small intestine though are of benefit physiologically (Delzenne et al 2020; Dietary Fibre 2015; Mackowiak, Torlinska-Walkowiak & Torlinska 2016).
For convenience, dietary fibre is classified as either soluble or insoluble based on water solubility. Soluble fibre includes cellulose, parts of hemicelluloses and lignin while insoluble fibre includes pentosans, pectin, gums, and mucilage. Both types have different functions in the body (Mackowiak, Torlinska-Walkowiak & Torlinska 2016).
What does dietary fibre do?
The physiological functions of fibre in the body are vast. It helps decrease intestinal transit time for waste and gives bulk to stools preventing constipation. It has an important role maintaining a healthy gut microbiota. It helps reduce bad cholesterol (LDL), and overall, maintains healthy total cholesterol levels. Finally, it reduces blood sugar levels after we have consumed a meal and improves glycaemic responses to foods (Delzenne et al 2020; Kieffer, Martin & Adams 2016; Mackowiak, Torlinska-Walkowiak & Torlinska 2016).
Many of the above functions are beneficial in the prevention of chronic diseases such as cardiovascular disease, colorectal and breast cancer, and diabetes mellitus. Fibre can also help with weight maintenance by increasing satiety making us feel fuller for longer (Mackowiak, Torlinska-Walkowiak & Torlinska 2016).
How much do we need?
To achieve the benefits mentioned above, adult men and women (19-70 years old) need to consume 30 and 25 grams of fibre daily. Adolescents and children require less. It should be noted that high-fibre diets, at intakes above the dietary recommendations, may interfere with nutrient absorption. Fibre-rich foods contain phytic acid which negatively affects the absorption of magnesium, iron, and zinc. Phytic acid is found predominantly in bran and beans (Dietary Fibre 2015; Mackowiak, Torlinska-Walkowiak & Torlinska 2016).
Where do we find dietary fibre?
Fruit and vegetables, oats, legumes, bran and wheat products in their wholegrain form – not highly refined – plus nuts and seeds. Eat the skin of washed fruit and vegetables as the skin is a rich source of fibre. Replace white highly processed foods like white bread and rice for hemp flour or hemp protein, wholegrain bread and brown rice to increase fibre intake (Dietary Intake 2015).
Take home message:
This column is not intended as medical advice but rather to provide information for educational purposes. Consult with your GP or other medical professional regarding the applicability of any of the information provided.
Delzenne, NM., Olivares, M., Neyrinck, AM., Beaumont, M., Kjolbaek, L., Larsen, TM., Benitez-Paez, A., Romani-Perez, M., Garcia-Campayo, V., Bosscher, D., Sanz, Yolanda & van der Kamp, JW, 2020, Nutritional interest of dietary fiber and prebiotics in obesity: Lessons from the MyNewGut consortium, Clinical Nutrition, Vol. 39, pp. 414-424.
Dietary Fibre, 2015, New Zealand Nutrition Foundation, viewed 25 February 2020, <https://nutritionfoundation.org.nz/sites/default/files/150116%20Dietary%20Fibre%20White%20Paper.pdf>
Kieffer, DA., Martin, RJ & Adams, SH, 2016, Impact of Dietary Fibers on Nutrient Management and Detoxification Organs: Gut, Liver, and Kidneys, Advances in Nutrition, Vol. 7, pp. 1111-21.
Mackowiak, K., Torlinska-Walkowiak, N & Torlinska, B, 2016, Dietary fibre as an important constituent of the diet, Postepy Hig Med Dosw (Online), Vol. 70, pp. 104-109.