Understanding Dietary References

While most people are capable of determining, in a general sense, what is a healthy food and what is not, there are fewer people that can look at a food label and genuinely understand the information provided, and I would wager even fewer understand where the numbers on the food label come from or how they were determined. In this article, we will understand how dietary reference intakes are determined and who determines them for the population.

Dietary Reference Intakes
When you look at a food label or you hear recommendation from your doctor or dietician on a nutrient, they are referring to the established dietary reference intake (DRI) guide. This guide is broken up into 4 distinct portions, detailed here with calcium as our example:

Estimated Average Requirements (EAR)

This portion of the DRI is the foundation to the entire dietary reference intake, and the others stem off of this one. The estimated average requirement is, as the name indicates, the average number [1]. So, if we were to consider an entire population like the United States, for example – roughly 300 million people – then the estimated average would take into account on 50% of that population; in this case, 150 million people. This average gives us a foundational reference point by which to set the more readily used terms discussed in just a second.

For example, the EAR for calcium is 800 mg/day [2]. This number would satisfy the need of 50% of the population. You may or may not fall within that 50% - that is a risk you likely do not want to take, so the EAR is only used as a starting number and is rarely talked about in comparison to the other dietary references.


Recommended Daily Intake/Allowance (RDI/RDA)

Meanwhile, the recommended daily intake (also interchangeably named the recommended daily allowance, RDA) is the most well-known, because this is the reference that most recommendations are based off. The reason for that is the fact that it covers a much greater amount of the population, because it is two standard deviations above the average/EAR. That said, this increases the percentage of the population covered in their body’s nutrient needs from 50% to 98% - which is about 294 million people in the United States [2]. This is the reference that your doctor or dietician would likely recommend.

For example, the RDA for calcium is 1000 mg/day [2], so 98% (294 million people) of the population would be consuming sufficient calcium for health if they consumed that amount per day.

The EAR is the 50% so it sets in the middle of the bell curve, and then the movement of 2 standard deviations leads to the creation of the RDA, covering ~98% of the population.

Acceptable Intake (AI)

The acceptable intake (AI) is an intake that is used when an RDA cannot be established for a particular nutrient; it offers a safe range of consumption [1]. If a person consumes within that acceptable intake range, then there is a lowered chance of negative effects on the body.

For example, if calcium did not have a recommended daily allowance, it would have a range called the acceptable intake.


Why do some nutrients not have a recommended daily allowance (RDA)?
Some nutrients do not have RDAs, because the estimated average requirement (EAR) has not been established. The main reason for there not being a set EAR is the lack of direct research, literature on the matter [1].

How is the acceptable intake (AI) determined, then?
Although there may not be enough literature to determine an EAR, the acceptable intake is determined via observational and experimentally determined estimates for each specific group of healthy peoples [1]. So, by looking back through the intakes of previous people and seeing their health markers, it is possible to assume that certain levels of that intake are acceptable to maintain normal body function [3].

Is the acceptable intake as definitive as the recommended daily allowance?
No. The recommended daily allowance assumes that there is enough research to determine a numerical value that, if applied/consumed by the correct group, would ensure nutritional safety [3]. The acceptable intake is simply a guess based on previous experience [3].

Upper Limit (UL)

This is the point at which a certain level of nutrient intake could start posing a risk to one’s health [1]. As a person consumes above this point repeatedly, the more they consume, the higher the threat to their health from overconsumption.

For example, the upper limit for calcium is set to 3000 mg/day. As such, if you were to consume 3200  mg/day consistently, the body may have trouble regulating the excess calcium and side effects (kidney stones, constipation, etc.) could occur [4]. Then, if a person were to consume 4500 mg/day consistently, the risk of these same side effects (and others) increases directly. 


Who establishes these dietary references?
These references are analyzed and determined by the Food and Nutrition Board of the Institute of Medicine [5].

How often are these references updated?
I could not find much information on this, but it seems as if the dietary references are updated on an information basis; so, if a noticeable amount of research confirms a need for a change in a particular nutrient, the change is then made.

Consequences of not meeting nutrient references?
Obviously, each nutrient has its own reference numbers and the consequences depend on what said nutrient does for the body in terms of health. In almost all cases nutrient deficiency and overconsumption lead to chronic illness. Luckily, while these numbers are as scientifically sound as possible, our body is typically able to regulate most nutrients effectively enough for us not to notice any isolated days of deficiency or over consumption. Still, these references, if followed, will lead to a clear, accurate numerical marker for which to strive to attain maximal health in terms of nutrition intervention.

Are references universal?
Absolutely not. For example, a child will need more calcium than an adult due to growth patterns. These special circumstances apply to all kinds of situations and vary from nutrient to nutrient.


SUMMARY

To sum up, dietary references are around to give us a scientifically sound indication of our nutrition needs, based on our bodily circumstances (pregnancy, healthy, growing, age, etc). The most important nutrition reference is the recommended daily intake (also known as the recommended daily allowance), because it covers the majority of a population. If the recommended daily intake cannot be determined, a “best educated guess” is used known as the acceptable intake.

Writer: Nicolas Verhoeven

                                                                                                Citations

[1] What are Dietary Reference Intakes? - Dietary Reference Intakes - NCBI Bookshelf. (n.d.). Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK45182/

[2] https://www.nal.usda.gov/fnic/DRI/DRI_Tables/recommended_intakes_individuals.pdf. (n.d.). Retrieved December 22, 2015, from https://www.nal.usda.gov/fnic/DRI/DRI_Tables/recommended_intakes_individuals.pdf

[3] 5 Using the Adequate Intake for Nutrient Assessment of Groups | Dietary Reference Intakes: Applications in Dietary Assessment | The National Academies Press. (n.d.). Retrieved from http://www.nap.edu/read/9956/chapter/11

[4] Dietary Supplement Fact Sheet: Calcium — Health Professional Fact Sheet. (n.d.). Retrieved from https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/

[5] Nutrient Recommendations : Dietary Reference Intakes (DRI). (n.d.). Retrieved from https://ods.od.nih.gov/Health_Information/Dietary_Reference_Intakes.aspx

 

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