Dietary reference intakes (DRIs) are a set of reference values for vitamins, minerals, and other nutrients important to human health. The values provide guidance on appropriate consumption levels for optimum health and safety. DRIs are specific to age group, gender, and for women, reproductive status.
DRIs are a set of figures intended to be used in planning and assessing diets of individuals and groups. They are based on data that applies to American and Canadian populations and replace the previously issued recommended dietary allowances (RDAs) in the United States and recommended nutrient intakes (RNIs) in Canada.
Health is strongly affected by the food that people eat, and proper diet can prevent, delay, or even treat certain diseases and disorders. Research on dietary vitamins and minerals in the 1920s and 1930s led to the publication of the first RDAs in 1941 by the Food and Nutrition Board of the National Academy of Sciences. These early RDAs were based on the amount of each vitamin or mineral that was needed by the majority of the population (97%–98%) to prevent symptoms of corresponding nutrient-deficiency diseases. For example, the RDA for vitamin A was set at a level that would prevent symptoms of night blindness. The introduction of RDAs gave a boost to food fortification programs that helped eliminate many vitamin deficiency disorders, such as pellagra, which is caused by niacin deficiency.
The RDAs were reviewed about every five years, and the values were adjusted as additional research became available, but for many years the underlying assumption remained one of setting dietary intake at the level needed to prevent disease. Multivitamin dietary supplements had been in use for many years, but by the early 1980s, single-ingredient dietary supplements claiming to boost athletic or sexual performance, increase energy, prevent disease, or control weight had become much more common. Research on these dietary supplements showed that some vitamins and minerals taken in quantities larger than the RDA appeared to provide benefits to healthy individuals, but the same supplement taken in too large a quantity could be harmful. The Institute of Medicine of the National Academy of Sciences decided that an expanded set of reference values was needed to incorporate this new research and provide better nutrition guidance to both health professionals and consumers. In 1997, in cooperation with nutrition authorities in Canada, they began replacing RDAs (and RNIs in Canada) with the first Dietary Reference Intakes.
DRIs are intended to apply only to people who appear healthy, as people with specific health concerns may have different requirements. The DRIs are calculated based on the nutritional needs of different age groups—infants 0–6 months and 6–12 months; children 1–3 years, 4–8 years, and 9–13 years; and adolescents 14–18 years. Adults are grouped by gender and are further subdivided into women who are pregnant, women who are breastfeeding, and sometimes into younger and older adults, depending on the nutrient. The values for each nutrient are measured against a specific reference goal. Examples of these goals include preventing symptoms of a nutrient deficiency disease, maintaining normal growth, maintaining a specific level of the nutrient circulating in the blood, or preventing symptoms associated with nutrient excess.
Four reference values make up the DRIs for micronutrients:
Macronutrients are nutrients that provide calories (energy) and are needed in higher amounts. These include carbohydrates, fats, and proteins. Fiber is an included nutrient, but it does not provide energy. In the body, carbohydrates, proteins, and fats can, in some cases, be used interchangeably. In addition, it is not possible to link specific quantities of these macronutrients to the prevention or development of chronic diseases, such as diabetes and cardiovascular disease. In place of DRIs, the Institute of Medicine has developed Acceptable Macronutrient Distribution Ranges (AMDRs) for energy-yielding nutrients. AMDRs are expressed not as absolute numbers but as a percentage of total energy (calorie) intake.
DRIs are intended as guidelines for population groups, not individuals. Although they assign values for daily intake of nutrients, these values are intended to apply over time. Except in cases of acute megadoses, the effects of too much or too little of a nutrient develop gradually over time. In any given day, an individual may eat more or less than the DRI of a particular nutrient and still remain healthy, so long as their average intake over time complies with recommendations.
DRIs are intended to be applied to a healthy population. Individuals under the supervision of a healthcare professional may be advised to take more or less of particular nutrients than the DRIs indicate. In this situation, the advice of the healthcare professional should be followed.
Certain people, such as vegans, have dietary needs that may be satisfied only with very carefully controlled diets or additional dietary supplements.
Nutrients interact with each other and with pharmaceuticals and herbal remedies. These interactions are not entirely understood and may affect the absorption, utilization, and excretion of various vitamins and minerals in ways that change the RDA.
The four components of the DRI are intended to provide more guidance than a single number alone would provide. However, they are not without critics. Some criticism stems from statistical assumptions made in the calculations; other critiques are based on the fact that different forms of certain nutrients have a different bioavailability. For example, iron in meat is more easily absorbed than iron in plant foods, and the vitamin E in dietary supplements is more biologically active than vitamin E in food. Although this should not be a source of confusion to healthcare professionals, it can be confusing to the average consumer.
The greatest controversies among experts are over the UL. These center around five areas:
DRIs continue to be researched and revised as more data becomes available. Despite any surrounding controversy, DRIs offer both healthcare professionals and individual consumers some guidelines about the benefits and dangers of nutrient consumption.
Parents should discuss DRIs with a healthcare professional who can translate them into practical healthy eating tips for use in providing a healthy diet for their children. A diet high in fruits and vegetables and low in fats will meet most DRIs for both children and adults.
See also Academy of Nutrition and Dietetics ; American Diabetes Association ; Anti-aging diet ; Biotin ; Calcium ; Calories ; Carotenoids ; Choline ; Dietary counseling ; Dietary supplements ; Fiber ; Fluoride ; Folate ; High-fiber diet ; Iodine ; Iron ; MyPlate ; Vitamin D .
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