What Do the RDA, AI, and UL Mean?

The Dietary Reference Intakes (DRIs) are the nutrient reference values used in the United States and Canada, set by the National Academies of Sciences, Engineering, and Medicine. For most nutrients they give two numbers that matter to you: the Recommended Dietary Allowance (RDA), an intake that meets the needs of nearly all healthy people (97% to 98%), or an Adequate Intake (AI) where the evidence isn’t strong enough for an RDA; and the Tolerable Upper Intake Level (UL), the most you can take daily without likely harm. Between the two, your usual intake covers your needs without likely harm; it’s judged as an average over time, not meal by meal.

This article is general information, not medical advice.

The Four Values

The US Office of Dietary Supplements (ODS) summarizes the DRIs this way:

Value	What it means
Estimated Average Requirement (EAR)	Meets the needs of half of healthy people; used mostly for assessing groups
Recommended Dietary Allowance (RDA)	Meets the needs of nearly all (97% to 98%) healthy people; the target for an individual
Adequate Intake (AI)	Assumed to be adequate; set when there isn’t enough evidence for an RDA
Tolerable Upper Intake Level (UL)	The most you can take daily without likely adverse effects

Each is set by age, sex, and life stage, with separate values in pregnancy and lactation. Being below the RDA doesn’t mean you’re deficient: the RDA is set high enough to cover people with the highest needs, so most people need less. The UL isn’t a target: above it, intake is no longer known to be safe.

For sodium, the 2019 report added a different kind of value, the Chronic Disease Risk Reduction Intake (CDRR): 2,300 mg a day for adults, above which reducing intake is expected to lower chronic disease risk. See How Much Sodium Should You Eat, and Why Does Potassium Matter Too?

Some Examples for Adults

From the ODS’s fact sheets:

• Vitamin C: an RDA of 90 mg a day for men and 75 mg for women (people who smoke need 35 mg more), and a UL of 2,000 mg.
• Vitamin D: an RDA of 15 µg (600 IU) a day up to age 70 and 20 µg (800 IU) over 70, and a UL of 100 µg (4,000 IU).
• Magnesium: an RDA of 400 to 420 mg a day for men and 310 to 320 mg for women, depending on age. Its UL, 350 mg, counts only supplements, since magnesium from food doesn’t pose a risk to healthy people.

Magnesium shows why a UL must be read carefully: some count everything you eat, while others count only supplements and fortified foods, so comparing a food log with them would be wrong.

Averages Over Time

The RDA and the AI are average daily intakes over time, as the ODS defines them. One day below the RDA isn’t a shortfall; what matters is your usual intake, so an average over a week or more is a better guide than any single day. The UL, by contrast, is defined as a maximum daily intake.

Following It in Kaizora

Kaizora comes with default reference ranges from the DRIs for adults, by your sex and age: a nutrient below its RDA, or its AI where there’s none, is flagged as mild, and above its UL, or sodium’s CDRR, as moderate. Since they’re averages, each day is judged on the total of the 7 days ending it against seven times the daily value, so one unusual day doesn’t flag. Falling short is common, so the “below” ranges flag without notifying you, while going over an upper limit does. A DRI whose basis isn’t a nutrient Kaizora tracks is left out, such as magnesium’s UL, which counts only supplements, and protein’s RDA, which is set per kilogram of body weight. Values for pregnancy and lactation aren’t applied yet.

Your nutrients come from the foods you log on Food Log and from imports. Each default’s popover says what the guideline says and who published it; defaults can’t be changed, but each can be hidden, or kept from notifying.

The Short Version

• The RDA covers nearly everyone’s needs; the AI stands in where evidence is thinner.
• The UL is the most you can take daily without likely harm; some ULs count only supplements.
• Being under the RDA isn’t the same as being deficient.
• Judge intake as an average over days, not by one day.

Sources

• Institute of Medicine, Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (Washington, DC: The National Academies Press, 2006). nap.nationalacademies.org/catalog/11537
• National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes for Sodium and Potassium (Washington, DC: The National Academies Press, 2019). nap.nationalacademies.org/catalog/25353
• Office of Dietary Supplements, National Institutes of Health, Nutrient recommendations and databases.
• Office of Dietary Supplements, fact sheets for health professionals: Vitamin C, Vitamin D, and Magnesium.