What Happens if an RDA Is Not Defined for a Nutrient?

November 2, 2025 •

3 min read

According to the Dietary Reference Intakes (DRIs), when there isn't enough scientific evidence to establish a Recommended Dietary Allowance (RDA) for a nutrient, an Adequate Intake (AI) is set instead. This critical substitution helps guide dietary planning, but what does this mean for consumers and nutritional science?

Quick Summary

When a Recommended Dietary Allowance cannot be established, health organizations use an Adequate Intake level based on observed nutrient consumption in healthy people. This serves as a dietary target, providing guidance for intake even with limited scientific data for a specific nutrient. This approach addresses the nutritional needs of healthy individuals.

Key Points

Adequate Intake (AI) is Used: When an RDA cannot be set due to insufficient scientific evidence, an AI is established instead.
Less Precise but Still Useful: An AI is a less precise estimate than an RDA, but it still provides a recommended daily intake based on observations of healthy populations.
Higher Risk of Inadequacy: Because an AI is not based on a specific EAR, the probability of an individual's intake being inadequate is unknown and potentially higher than with an RDA.
A Balanced Diet is Key: Following a balanced, whole-food diet is the most reliable way to meet the needs for nutrients with an AI, mitigating the uncertainty.
Not a Sign of Unimportance: The absence of an RDA does not mean a nutrient is unimportant; it simply reflects the current state of scientific research.
Consult a Professional: A registered dietitian can provide personalized guidance regarding nutrients with only an AI, especially for those in at-risk groups.

From RDA to Adequate Intake: The Scientific Process

In the world of nutrition, guidelines are established by health authorities to help people maintain a healthy diet. The most precise and well-known of these is the Recommended Dietary Allowance (RDA). An RDA is set when there is sufficient scientific evidence to determine an Estimated Average Requirement (EAR)—the median intake level estimated to meet the requirements of half the healthy individuals in a group. The RDA is then calculated to cover the needs of 97–98% of healthy people within a life-stage and gender group.

However, the scientific evidence isn't always complete for every single nutrient. Sometimes, research is limited, or the data on average requirements is not conclusive enough to establish a definitive EAR. This is where the concept of an Adequate Intake (AI) comes into play. An AI is a recommended average daily intake level based on observed or experimentally determined approximations of nutrient intake by a group of apparently healthy people. It is meant to serve as a guide when an RDA cannot be scientifically determined. This provides a useful, evidence-based target for intake, even if it is not as precise as an RDA. For example, the DRIs for infants are based on AIs derived from nutrient values found in human breast milk.

Practical Implications for Your Diet

For consumers, understanding the difference between an RDA and an AI is important for interpreting nutritional advice and food labels. An RDA represents a robust, statistically sound target, while an AI is a more cautious recommendation based on less comprehensive data. Both are meant to be goals for usual intake, ensuring you meet your nutritional needs. The primary takeaway is that a lack of an RDA does not mean a nutrient is unimportant or that a need for it doesn't exist. It simply indicates that the exact requirement is not yet fully understood by science, but an intake level has been estimated to maintain adequacy.

Potential Health Consequences

While an AI is generally considered sufficient for most healthy individuals, relying on potentially incomplete data carries some risks. For a list of potential consequences, including an increased risk of deficiency and difficulty assessing individual intake, please refer to {Link: Canada.ca https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/fn-an/alt_formats/hpfb-dgpsa/pdf/nutrition/dri_tables-eng.pdf}.

Understanding the Dietary Reference Intakes (DRIs)

The Dietary Reference Intakes (DRIs) framework provides a comprehensive system for nutrient guidance. To learn more about the four main DRI values (EAR, RDA, AI, and UL) and their definitions, please see {Link: Canada.ca https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/fn-an/alt_formats/hpfb-dgpsa/pdf/nutrition/dri_tables-eng.pdf}.

Comparison Table: RDA vs. AI

For a detailed comparison table outlining the differences between RDA and AI in terms of scientific evidence, precision, coverage, determination, and risk of inadequacy, please visit {Link: Canada.ca https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/fn-an/alt_formats/hpfb-dgpsa/pdf/nutrition/dri_tables-eng.pdf}.

How to Approach Nutrients Without an RDA

If a nutrient only has an AI, a varied and balanced diet rich in whole foods is typically the best strategy. Consuming diverse fruits, vegetables, proteins, and healthy fats helps meet or exceed the AI. Consulting a registered dietitian can ensure optimal intake, especially for at-risk groups or those with specific health concerns.

A balanced diet is key to navigating any nutritional recommendations, including those based on Adequate Intake values. Further research on specific nutrients can be found through authoritative sources like {Link: NIH https://www.ncbi.nlm.nih.gov/books/NBK221374/}.

Conclusion

The absence of an RDA means insufficient scientific data for precise requirements, leading to the establishment of an Adequate Intake (AI) as a valuable dietary target. While less precise than an RDA, an AI still guides nutrient intake. Individuals can confidently navigate these ambiguities by prioritizing a diverse, whole-foods-based diet and consulting nutrition experts.

Frequently Asked Questions

The RDA is a highly specific, statistically-derived intake level designed to meet the needs of 97–98% of the healthy population, based on a known Estimated Average Requirement (EAR). The AI is an estimate used when there isn't enough evidence to set an RDA, based on observed intakes of healthy people.

No, it does not mean the nutrient is unimportant. It simply indicates that there is not enough robust scientific data to establish a more precise RDA. The nutrient is still considered essential for health.

An AI is assumed to be sufficient for most healthy people, but it is an approximation. There is an unknown, and potentially higher, probability of inadequacy for individuals whose needs exceed the general population's observed average.

Scientists determine an AI by observing and analyzing the nutrient intake of healthy population groups. This may involve examining the average nutrient levels in breast milk for infants or observing dietary patterns in healthy adults.

Yes, you can use an AI as a nutrient intake goal, especially in the absence of an RDA. It provides a useful target to help ensure nutritional adequacy, though it is less precise than an RDA.

While rare for established nutrients, if a component lacks both, it's best to focus on a varied and balanced diet. This approach helps ensure you receive a wide spectrum of nutrients, including those less researched. Any supplementation should be discussed with a healthcare provider.

Several factors can lead to insufficient data, including limited research studies, lack of a reliable indicator for measuring the nutrient in the body, or significant variation in individual requirements that makes a single average hard to establish.