The Scientific Basis for Dietary Reference Intakes
The Dietary Reference Intakes (DRIs) provide a set of reference values used to plan and assess the nutrient intakes of healthy people. The DRIs include four main reference values:
- Estimated Average Requirement (EAR): Meets the needs of half the healthy individuals in a group and is used to set the RDA.
- Recommended Dietary Allowance (RDA): Sufficient to meet the needs of nearly all (97–98%) healthy individuals. Can only be set if an EAR is established.
- Adequate Intake (AI): Based on observed or experimentally determined nutrient intake approximations by a healthy group. Used when insufficient evidence exists for an EAR and RDA.
- Tolerable Upper Intake Level (UL): The maximum daily intake unlikely to pose adverse health risks.
Why Insufficient Data Leads to an AI
The primary reason a nutrient receives an AI instead of an RDA is insufficient scientific evidence to determine a precise Estimated Average Requirement (EAR). This can be due to limited human data, variability in requirements, or ethical constraints in conducting necessary studies, particularly in infants. For infants, the AI is often based on the nutrient intake from healthy, exclusively breastfed babies, as breast milk is considered the standard for infant nutrition.
How an Adequate Intake is Determined
Determining an AI relies on observational or experimental data from healthy populations, involving more scientific judgment than the statistical calculation for an RDA. Methods include observing nutrient intake in healthy groups showing no deficiency signs, using data from controlled experiments at the lowest adequate intake level, or combining various data sources, as seen with calcium.
Implications for Consumers and Health Professionals
For consumers, an AI serves as an intake target, similar to an RDA. Meeting or exceeding the AI suggests sufficient intake. However, intake below the AI doesn't definitively indicate deficiency due to the lower certainty level. For health professionals, an AI indicates the need for further research.
Nutrients That Have an Adequate Intake
For a list of nutrients that have an Adequate Intake, please refer to {Link: Canada.ca https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/dietary-reference-intakes/questions-answers.html}.
Comparison: Adequate Intake (AI) vs. Recommended Dietary Allowance (RDA)
| Feature | Adequate Intake (AI) | Recommended Dietary Allowance (RDA) |
|---|---|---|
| Scientific Basis | Based on less definitive evidence. | Based on more robust evidence, derived from an EAR. |
| Certainty Level | Less certain. | More certain. |
| Derivation Method | Set when an EAR cannot be established due to insufficient data. | Calculated from the EAR. |
| Use Case | Intake at or above is likely adequate. | Reliable target to ensure sufficiency. |
| Assessment of Deficiency | Intake below may indicate risk, but risk degree is hard to quantify. | Intake below significantly increases inadequacy risk. |
The Path Forward in Nutrition Science
An AI signifies the need for further research. While an AI is a safe and reasonable intake target in the absence of comprehensive data, it may be replaced by an RDA as new research emerges. The AI approach ensures recommendations are based on the best available science while acknowledging limitations. Detailed information on setting DRIs is available from the National Academies.
Conclusion
A nutrient is assigned an Adequate Intake (AI) instead of a Recommended Dietary Allowance (RDA) when there is not enough solid scientific evidence to precisely determine the average requirement for that nutrient within a population. Although less certain than an RDA, the AI provides a valuable dietary target.
