EAT FOR HEALTH Australian Dietary Guidelines

EAT FOR HEALTH – AusTRALiAn diETARy guidELinEs

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Guideline 2

Cancer

•   Colorectal cancer: There is recent evidence suggesting that consumption of one to three serves of cereals

high in dietary fibre per day is associated with reduced risk of colorectal cancer in adults (Grade C; Evidence

Report, Section 6.2).397,467-471 Although previously the WCRF report noted a probable relationship, it recently

reviewed the evidence and found it convincing that fibre-rich foods offer protection against colorectal cancer

(see Appendix F).43,472 This is also supported by a recent systematic review and dose response meta-analysis

of prospective studies showing that three serves of wholegrain and high fibre cereals per day reduced the risk

of colorectal cancer.^473

•   Other cancers: Recent evidence is inconclusive for an association regarding the consumption of grain (cereal)

foods and risk of other cancers in adults (Evidence Report, Section 6.1).

2.3.3 How consuming grain (cereal) foods, mostly wholegrain and/or high cereal

fibre varieties may improve health outcomes

Much depends on which wholegrain is being considered.4 74 For example, oat ß-glucan binds with bile acids, so

the liver breaks down more cholesterol to maintain a supply of bile acids. Wheat does not contain these soluble

fibres. Also, the slow rate of glucose delivery from oats reduces the requirement for insulin.^475 The slower rate of

absorption created by the presence of dietary fibre from some grain (cereal) foods can also influence appetite.

For example, oat ß-glucan has been shown to have effects on postprandial cholecystokinin levels, decreased

insulin response and extended subjective satiety in overweight adults.^476 Other sources of dietary fibre, such

as psyllium may act in a similar fashion. Grain (cereal) foods also contain starch (complex carbohydrate) that

may be resistant to digestion in the small intestine (resistant starch) and may help to provide a more protective

environment in the colon, particularly in the context of meals.^477 Note that as some degree of processing is

applied to most grains (cereals) to aid digestion, the effects can be significantly influenced by the technology

applied in processing and cooking.^478

Because wholegrains contain more nutrients and phytochemicals, concentrated in the bran and germ,^479 they are

likely to have greater effects than refined grains (cereals). Wholegrains contain phenolic compounds with strong

anti-oxidant capacity that may be protective against processes involved in the pathology of type 2 diabetes,

cardiovascular disease and cancer.^480 Choosing wholegrain options may also assist with satiety and help in not

over consuming food beyond energy (kilojoule) requirements.

The 2003 edition of the dietary guidelines discussed the glycaemic index (GI) of individual foods as a physiologically

based classification of carbohydrate-containing foods according to their potential to raise blood glucose.^36

Various factors such as the particle size of milled grains (cereals), the ratio of amylose to amylopectin, the degree

of starch gelatinisation and the presence of other food components such as viscous soluble fibres, fat, protein

and organic acids may affect the GI value of a food and may limit practical application.^199 Additionally, the accuracy

with which published values can be used to predict GI when foods are eaten together as a meal is limited.^481

lower GI diets may assist in the management of type 1 and type 2 diabetes but are not associated with weight

loss (see Chapter 1).36,198 Further research on GI and health outcomes may be required to investigate other

potential associations.

The 2003 edition of the dietary guidelines also noted that consumption of dietary fibre assists in maintaining the

health and function of the digestive system, for example in preventing constipation.35,36

2.3.4 Practical considerations: enjoy grain (cereal) foods, mostly wholegrain and/or high

cereal fibre varieties

Consuming at least four to six serves of grain (cereal) foods, mostly wholegrain and/or high cereal fibre varieties,

per day is recommended for Australian adults, while the amount recommended for children and adolescents

depends on their age and sex (see Tables 2.8 and 2.9), ranging from four serves a day for 2–8 year olds to seven

a day for older adolescents.

The companion resources provide more detailed information on the recommended number of serves and serve

sizes of grain (cereal) foods required for different population groups. Discussion of dietary patterns and the

environment is included in Appendix G.