RDA and UL Nutrient Standards

RDA and UL Nutrient Standards


When first studying nutrition, it is not uncommon
for beginning students to ask, “How much of a specific nutrient do I need for optimal
health?” That seems like simple questions, but it isn’t. The question assumes there are
individual recommendations and that optimal health is clearly defined. Neither of those
are true. In fact, there are no nutrition standards that provide specific requirements
for individuals and the term ‘optimal health’ is an oft debated, vague concept. What we do have, however, are RDAs or the
Recommended Dietary Allowances. The RDAs give specific recommendations for nutrients. So,
they provide the clearest answer to that beginning student’s question. It is important, however, to understand how
RDAs are set so we can better understand what it means to have a diet that meets the RDA
recommendations. You have access to the RDA charts in your book and on-line materials.
And, here on the screen, I have the RDAs for vitamins If we look at the RDAs, they are.. First of
all, the idea they are into groups. If we look at a specific group. So we’ll look at these infants from 0-6 months of age, there is a specific amount of a nutrient…this
one with vitamin A… that is being recommended. What that means is that individuals within
that group need to consume, on average, that amount of the nutrient. So, here is one of our first key concepts. The RDAs are group recommendations. They are not individual requirements. We look at the groups, we can see there are groups by ages. So, we have those infants and we have different age groups, 1 to 3, 4 to 8, on down the list. We have other groups by gender. So we have males and females. And then reproductive status with pregnancy and lactation. So group recommendations, not individual requirements. If we look at a specific group within there and more specific what that number means. Let’s pick these 19 to 30 year old females
and we’ll pick vitamin C. We can see all of the specific recommendations, but specific
to that group we are looking at (those 19 to 30 year old females) it says 75 milligrams. But what does it mean, if you have on average, if you are in that group, 75 milligrams. The focus of RDAs is to prevent nutrient deficiencies. So if you consume, on average, 75 milligrams a day you are going to prevent scurvy. It
does not give any recommendation related to your risk of common colds or cancer. So there is another key concept. The focus of RDAs, values that are listed, are to prevent nutrient deficiencies. They are not related to preventing chronic disease or that vague concept of optimal health. I want to speak a little bit more how they come up with that one specific number. I have a graph here here that will describe how they come up with such a number. And we will think about what happens when we consume more of a nutrient. Now each of these nutrients we are talking about is an essential nutrient. And, of course, if we take in the amount that is consumed
and we are looking at the amount that is needed within that group, the 19-30 year old females in this instance, if they take in zero amount on average, they are all going to have a
deficiency. It is not meeting the needs. So, we have to take in more. As you are taking
in more of that nutrient, eventually there will be some people within that group, a number
of people within that group, where it is enough to prevent deficiencies. If we look at the
whole group, what research has found is that we end up with a bell shaped curve. Meaning that individuals, as you consume more within, individuals within that group, more and more meet their needs. Then eventually there are some who at the very end who need a bit more
on average. So we have this range of actual needs. Some people need a bit more, other
need a little bit less, but on average we have this range on intakes to prevent deficiency. Now we have to communicate that to everyone
else within that group. We can see with the RDA they have just one number. We are not
going to communicate a range. That is complicated to communicate. So we look at this and think,
well what you could do is take the average. Look at that bell shaped curve and take the average. But the problem with using an average as your standard to communicate to that group is that if you have people eat towards the average, which some people do eat towards the RDA, that would be a lot of people that it would not be eating enough to meet or prevent a deficiency. So the RDAs are not set at the average. In
fact, RDAs are set at two standard deviations above the mean (average). This is where we set the RDAs. They are at the 97.5 percentile of needs to prevent nutrient deficiency. So a couple things we can now conclude here:
(1) RDAs are not minimums. A minimum would mean it is the amount you need to prevent
that deficiency. And we can see for most people, they actually require less than the RDA to
prevent that nutrient deficiency. (2) Another thing they are not, is they are not an average. So we said the average is too low. We are going to put it at that fuzzy
concept. It is a fuzzy concept. We are going to put it at the point at which nearly all healthy individuals will meet the amount to prevent a deficiency. So that is the RDAs. Fuzzy concept, not a
minimum, not an average, but it going to meet the needs of what most people require to prevent
a deficiency. Let’s go back to that introductory nutrition
student’s question of how much do I need. We are going to use the RDA to assess an individual
risk. Let’s have an individual. Have that individual consuming, an amount here. We are
just going to say we have an individual consuming …erase this here.. we have them consume
this amount. Day 1, one day of intake, and this is the amount they consume. It is just
a little bit less than the RDA. Well, we can see with this bell shaped curve
that most individuals actually require less than the RDA. So, we are going to say, in
all likelihood, that is enough. And that is what nutrition scientist do. When we use the
RDAs, use the RDAs, to assess individual risk (of deficiency) for individual. First of all,
we are not going to be concerned unless they have less than 75% of the RDA. So on average,
if you are consuming a little be less than RDA, probably okay. But once you get below
average

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