Dietary Guidelines

Dietary Guidelines

Dietary guidelines

Dietary goals for the American people were first recommended by the US Senate in 1977, followed by the first edition of the Dietary Guidelines for Americans in 1980. These were in turn used as a template for the Australian dietary guidelines that were introduced in 1980. A recent systematic review and meta-analysis concluded that when introduced, the US guidelines were not consistent with best available scientific evidence.

Since their inception, both the Australian and US dietary guidelines have evolved through regular revisions. Recent changes include removal of the recommended upper limit for individual sodium consumption from the Australian Dietary Guidelines(8)in September 2017, and the removal of the recommendation to limit both dietary cholesterol and total fat in the most recent edition of the Dietary Guidelines for Americans (2015-2020). Many features of current dietary guidelines remain identical or very similar to their initial versions. The current Dietary Guidelines for Americans continues to advise that saturated fats should represent no more than 10% of total energy intake. Similarly, the current Australian Dietary guidelines advise restricting intake of saturated fats, and current UK guidelines recommend not more than 35% of energy intake be derived from fat, with no more than 11% of this from saturated fat. Complementary with this view of fat, most guidelines recommend that carbohydrates should provide a significant portion of total energy.

Despite macronutrient intake recommendations on fat and carbohydrate forming a central tenet of most dietary guidelines, they are not supported by the balance of available evidence. A recent analysis of the methodology used to formulate the current edition of Dietary Guidelines for Americans (2015-2020) found that sound scientific methodology was lacking. This included more than 70 relevant randomised controlled trials published after 2000 being excluded from the evidence based used. Similar criticisms of improper methodology have been made regarding the current Australian Dietary Guidelines and Public Health England’s Eatwell Guide.

 

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Nutrient terminology

 

Nutrient Reference Values (NRVs) in Australia and New Zealand are based on current knowledge regarding the level of intake required to prevent deficiency states in an otherwise healthy population. These reference values apply to macronutrients, micronutrients and vitamins.

 

The Recommended Dietary Intake(RDI) for a group reflects the average daily intake to meet the requirements of 98% of individuals within that group.  The RDI exceeds the nutrient requirements of most healthy people and should not be confused with requirements.

 

Estimated Average Requirement(EAR) is the daily intake of a nutrient thought to be sufficient for 50% of individuals within a group. By definition, 50% of individuals consuming the EAR will not be meeting their daily requirements.

 

If there is insufficient data to determine RDI and EAR for a given nutrient, requirements can be expressed as an Adequate Intake (AI), an estimation of the nutrient intake necessary to maintain a healthy state. Adequate intake is often based on observational data.

 

The Upper Limit (UL) is the maximum daily intake of a nutrient that is likely to pose no risk of adverse effects. Intake of nutrients far exceeding the UL is considered to be ‘pharmacologic’ dosing, and in Australia requires a medical prescription.

 

It is important to note that these recommendations exclude groups such as children, adolescents and pregnant women.