The macronutrients are nutritional components present in foods in relatively large, gram amounts – these include protein, fat, carbohydrate and alcohol. Macronutrients provide energy for metabolism, the larger or more active you are, the greater your energy requirements are likely to be. The energy available from foods is measured in kilocalories of kilojoules, where 1 kilocalorie = 4.2 kilojoules.
The greater the energy content per gram of food, the more ‘energy dense’ the food. Foods high in fat are the most energy dense, while foods high in carbohydrates are the least energy dense. Energy, as available energy per gram of micronutrient is shown in the following table:
| Macronutrient | Calories/gram | Kilojoules/gram |
|---|---|---|
| Protein | 4 | 17 |
| Fat | 9 | 37 |
| Carbohydrate | 4 | 16 |
| Alcohol | 7 | 29 |
The micronutrients are nutritional components present in relatively small, milligram or microgram amounts – these include an array of vitamins and minerals. The more nutrients there are for a particular amount of energy, the more ‘nutrient dense’ the food. Vegetables for example, have relatively low energy density (because they are low in fat), but high nutrient density, since they are rich sources of many vitamins and nutrients.
Recommended Dietary Intakes (RDIs) were established in 1991. In 2006, Nutrient Reference Values (NRVs) were adapted for Australia and New Zealand which embrace RDI and Adequate Intake (AI).
Nutritionists in different countries have evaluated the experimental evidence regarding the level of nutrient intakes that are safe – not too high to cause toxicity yet adequate to prevent deficiency – and formulated RDIs for a range of nutrients. RDIs are expressed in terms of daily intakes that are considered adequate to meet the needs of most healthy people. Most nutrients are not needed every day, since they can be stored in the body to a greater pr lesser extent.
RDIs do not refer to the absolute needs of particular individuals, nor do they allow for factors such as illness or interactions with certain drugs, which may increase requirements. They incorporate a generous safety margin and allowance is made for gender and age. RDIs for the common nutrients are shown in the following table.
The RDI for energy varies according to age, gender and body weight and is expressed as a range to take individual variations into account. Unlike RDIs for nutrients, the RDIs for energy represent an average value and do not incorporate a safety margin.
A balanced diet provides adequate energy and nutrients to meet specified recommended dietary intakes that are designed to maintain long term health. In general, if your average daily intake of any nutrient, over a period of time, is less than two-thirds of the recommended level, then you may not be getting enough of an essential nutrient. The further your intake falls below this level, the greater the risk of deficiency. This could be due to not eating an adequate amount of food or to a poor choice of foods.
There are no recommended dietary intakes for fat, carbohydrate or alcohol. Optimal intakes of these macronutrients depend on your total energy intake and therefore are expressed as a percentage of total energy. An optimal balance of macronutrients provides 10 to 15% of total energy intake from protein, 30 to 33% from fat, not more than 5% from alcohol and remainder, about 47 to 60% from carbohydrate.