James G. Penland
After two years of reviewing the results of thousands of scientific studies and testimony from dozens of nutrition experts, the Food and Nutrition Board of the National Academy of Sciences’ Institute of Medicine released new intake recommendations for 2 vitamins and 12 minerals on January 9. The new Dietary Reference Intakes (DRIs) for Micronutrients covers the minerals arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium and zinc, and vitamins A and K.
DRIs for the minerals calcium, fluoride, magnesium, phosphorus, and selenium were released in earlier reports.
Cited in the report were more than 50 research publications based on studies conducted at our own Grand Forks Human Nutrition Research Center, part of the U.S. Department of Agriculture’s Agricultural Research Service. Center scientists were also among the experts invited to provide testimony on the health and functional consequences of micronutrient deficiencies and to make recommendations for optimal dietary intakes. One center scientist was involved in preparing the report.
DRIs represent the new approach to provide quantitative estimates of nutrient intakes for use in a variety of settings. They replace and expand the traditional Recommended Dietary Allowances (RDAs). The DRIs are actually a set of the following four reference values:
- Recommended Dietary Allowance (RDA) is the average daily dietary intake of a nutrient that is sufficient to meet the requirement of nearly all (97-98%) healthy persons.
- Adequate Intake (AI) for a nutrient is established when available data are insufficient to set an RDA but are sufficient to estimate an intake that would maintain nutritional adequacy in most people. The AI is based on observed intakes of the nutrient by a group of healthy persons.
- Tolerable Upper Intake Level (UL) is the highest daily intake of a nutrient that is likely to pose no risks of adverse health affects (toxicity) for almost all individuals. As intake above the UL increases, risk increases.
- Estimated Average Requirement (EAR) is the amount of a nutrient that is estimated to meet the requirement of half of all healthy individuals in the population.
According to the report, for healthy adults between the ages of 19 and 50 years, the following RDAs were set: copper (900 mcg/day), iodine (150 mcg/day), iron (males - 8 mg/day, females - 18 mg/day), molybdenum (45 mcg/day) and zinc (males - 11 mg/day, females – 8 mg/day). The abbreviation ‘mg’ is for milligram- one-thousands of a gram, and ‘mcg’ is for microgram - one-millions of a gram.
For the same age range, AIs were set for chromium (males – 35 mcg/day, females – 25 mcg/day), and manganese (males – 2.3 mg/day, females – 1.8 mg/day).
And ULs were set for boron (20 mg/day), copper (10 mg/day), iodine (1.1 mg/day), iron (45 mg/day), manganese (11 mg/day), molybdenum (2 mg/day), nickel (1 mg/day), vanadium (1.8 mg/day) and zinc (40 mg/day).
The report contains additional guidelines for other age groups and for pregnant and nursing females.
DAs, AIs and ULs are dietary guidelines for individuals, whereas EARs provide guidelines for groups and populations. Factors that might modify these guidelines, such as the ability to absorb the nutrients from different sources, nutrient-nutrient and nutrient-drug interactions, and intakes from food fortificants and supplements, are addressed in much greater detail than previously.
Remember that the DRIs include RDAs, as well as AIs, ULs, and EARs. Individuals should pay particular attention to RDAs and AIs as a goal for average daily intake, and to ULs as an indicator of safe intake. EARs will be used by dietitians and others planning diets, developing new foods, and setting policies for food supplies for groups and populations.
You can view the report on the National Academy of Sciences’ web site, www.nas.edu.