Rationale and framework
Principles of carbohydrate food choices
Carbohydrate nutrient and food goals
Translation from carbohydrate nutrients to foods
Considerations for target audiences
Although the scientific basis for dietary guidelines requires an understanding of physiology and health relationships, the guidance most helpful to consumers uses food-based terms (93). In preparing such guidelines, food traditions and beliefs must be taken into account and the total food intake should reflect practical issues, such as meal patterns, food status, celebratory or usual role, seasonal availability, affordability and sustainability. These, including the health priorities, are matters for national policy makers.
The principles are:
1. To acknowledge the socio-cultural context, lifestyle and stage of life-cycle, in food carbohydrate choice;
2. To give preference to food choices rather than to nutrient goals in carbohydrate food choices, and in so doing:a. Use food categories as a guide to chemically defined carbohydrate type.
b. Use numbers of portions (serving sizes) of foods from designated food categories in order to provide semi-quantitative food-based advice. This may imply that meal frequency would need to increase in some cultures, because the accommodation of enough carbohydrate food in the course of the day, without an excessive amount on any one occasion, requires more frequent servings and consumption;
3. To appreciate that many of the world's health problems are associated with inadequate carbohydrate intake, and potentially also associated with inappropriate carbohydrate intake;
4. To ensure the acceptability and practicality of any recommended change in carbohydrate food intake;
5. To acknowledge that there may be unintended consequences involved in carbohydrate food intake change, and also to ensure that risks involved in dietary changes from traditional diets is considered;
6. To monitor the intake of carbohydrate foods and, wherever possible, of chemically defined carbohydrate components of those foods in relation to health issues.
7. To ascertain whether food carbohydrate choices encourage biodiversity and are sustainable.
The minimum amount of carbohydrate in the human diet that is needed to avoid ketosis is of the order of 50 g/day in adults. Beyond this, additional energy needs are best met by nutrient-dense carbohydrate foods. There must, of course, be adequate intakes of protein (with essential amino acids) and essential fatty acids from fat. Moderate intake of sugar-rich foods can also provide for a palatable and nutritious diet.
There are a number of approaches to translating nutrient recommendations to food goals:
1. Recommending the total weight of food groups to be consumed. Various national food guides have suggested quantities of specific foods to be consumed, such as fruits and vegetables, and pulses, nuts and seeds.
2. Examining sources of carbohydrate foods in various diets, particularly diets which have desirable total carbohydrate intakes or from countries where the incidence of lifestyle diseases is low. Recommendations can then be made on the basis of intakes.
3. Examining major food groups which contain carbohydrate foods and recommending numbers of servings of those food groups. Numerous countries around the world, both developed and developing, have produced food guides with such groupings, and considering the level of agreement that exists for carbohydrate as a percent energy, these food guides are remarkably consistent in their advice.
4. Examining indices which exist to describe various physiological properties of carbohydrate-containing foods, such as glycemic index values and values from other indices which are presently being developed.
On the basis of the above approaches, and taking into account the principles for carbohydrate food choice, the following recommendations can be made:
1. A variety of foods should provide the carbohydrate in the diet, not a single or small number of sources.
2. Cereals, roots, pulses, fruit and vegetables are all components of a healthy diet throughout the world.
3. Cereal foods or root crops, where this is the main staple, should provide the major source of carbohydrate energy.
4. Intake of fruits and vegetables (including potatoes in developed countries) should be high. As well as being a valuable source of carbohydrate, fruit and vegetables are an important source of antioxidant vitamins and other food components.
5. Consumption of pulses, nuts and seeds should be encouraged. While this group often represents only a small amount of carbohydrate energy, these foods are a good source of protein and micronutrients. They should be consumed with cereals to optimize protein quality.
6. At least small quantities of milk products are desirable, even when low lactase activity exists, since these are a good source of protein and micronutrients.
These recommendations apply to all individuals over the age of two years, with adjustments as necessary for growth and the increased demand of pregnancy and lactation.
Achieving goals for intake of carbohydrates does not ensure nutritional adequacy. Carbohydrate foods provide a range of nutrients and other substances essential for health in addition to energy. It is therefore essential to consume a variety of foods in order to derive the full benefits of a high carbohydrate diet. Nutrients from foods require monitoring. For example, in Iran (94) carbohydrate foods include vegetables (250 g/day), fruits (210 g/day), pulses (20 g/day) and cereals (wheat at about 250 g/day and rice 110 g/day, uncooked). Wheat has mostly been consumed as bread with traditional pastries being festive foods. Recently, consumption of the latter has increased substantially with potential reduction of nutritionally useful food groups traditionally accompanying bread. This may not significantly impact on total carbohydrate intake, but could influence nutritional adequacy. Traditional methods of food preparation and preservation facilitate food choice variety, and promote nutritional benefits. Alteration of traditional practices may compromise such benefits. Ongoing monitoring may be required to guard against nutritional inadequacy.
Planners and policy makers need to:
1. Recognize dietary goals of at least 55% of total energy from a variety of carbohydrate sources.
2. Recognize the extent of change necessary in order to meet these goals (e.g. it may take considerable change in food production and consumption to meet goals in Western countries).
3. Understand that there must be a gradual transition in meeting new dietary guidelines and that new terminology will need to be gradually accepted.
4. Consider the effects of economic and cultural factors in achieving dietary goals.
5. Develop clear guides about the types and quantities of food recommended.
6. Develop methods to monitor food consumption to meet dietary goals.
Primary producers and processors need to:
1. Consider how existing and new technologies can be used to help meet dietary goals regarding the quantity and nutritional properties of food carbohydrates, as well as levels of micronutrients and other desirable food components.
2. Provide foods, such as breakfast cereals and snack foods that are high in NSP, low in energy density, and with a low glycemic index.
3. Increase the availability and convenience of fruits and vegetables.
4. Provide appropriate information to the consumer on food labels.
To facilitate individual choice
Provide easily understandable food-based guides for the consumer.