Tuesday, October 3, 2023

Recommended dietary intakes of various nutrients

To know if we are getting adequate nutrition, we need to know what is 'adequate'. This article aims to demystify the myriad numbers and acronyms specifying that.

Executive Summary

Our modern lifestyle can lead to nutritional deficiency because of various reasons. So it helps to know how much of each nutrient we should be eating daily. However, this part is filled with confusing terminology.

RDAs are Recommended Dietary Allowances per day. They differ for different ages, genders, and even life stages (such as pregnancy). When RDAs cannot be determined, we have Adequate Intakes (AI). These two are combined to give a number called Daily Value (DV), which is the RDA or AI for a young adult.

These are usually the values below which one can face health problems. Occasionally, politics and social issues are involved in deciding these cut–offs.

Also, these are values applicable for 95% of the normal people. Some healthy people may face problems in spite of taking these amounts. So, optimum intake numbers will be higher than this.

The Upper Tolerable Levels (UL) are sort of cut–offs for highest average daily consumption. But, these are not toxic levels. These are the levels that, if taken daily, are not healthy in the long term.

Finally, as more and more data becomes available, these numbers are changed by government agencies.

The article gives a table of latest numbers for many nutrients.

Are we getting enough nutrients from our food? Or do we need to supplement them in some way, such as eating fortified foods, or dietary supplements?

To answer this, we need to know how much of each nutrient should we be eating daily. This is where it gets a bit confusing. Let us see if we can make sense of the available information.

Nutrient deficiency

In earlier days, the life was simpler, and closer to the nature. Most people had adequate intake of most nutrients. So, there was less need for knowing about the required levels of nutrient intake.

Nowadays, our modern lifestyle leads to deficiencies of various nutrients, such as vitamins and minerals. There are various reasons for it, such as:

Over–farming and depleted top soil

Our farm soils have far less nutrients than earlier times, probably because of over–farming.

While fertilisers replace the big three components — nitrogen, potassium, and phosphorous, — micronutrients such as copper, manganese, chromium, have dipped down in levels in the soil. And if they are missing from the soil, there is no way they will come in our foods.

Food sources with low nutrient content

Our food sources are low in nutrition, as the focus is now on having better yields, and not better nutrient content. The grains have visibly changed over the last century. Instead of scrawny kernels that existed 100 years ago, we have big kernel sizes developed through hybrid techniques. Such grains are more pest resistant, giving far more yields. However, the focus is never on higher nutrient content, and such grains are often found to be low in nutrition.

Even animals are often given growth–hormones and antibiotics. This may give more milk or meat per animal. But the nutrient content is often much lower.

Inefficient supply cold–chain

From the time the plant is cut, the nutrients in it start falling, as the matter starts to decay. Unless the produce is immediately refrigerated, the consumer gets food which significantly depleted in nutrients. For this, we need efficient cold–chain storage and transport facilities. Many countries lack those resources.

Bad dietary habits and choices

We choose highly processed food which is dense in calories and poor in nutrient content. Often, we choose our food based more on taste and convenience, and less on freshness and nutrient content.

But, more on these issues in some other article.

The ramifications of nutrient deficiencies are plenty. There is a lot of literature available on the problems they lead to. Preventing that shortfall is the best option. However, we can do that only if we know how much of the nutrients we really need.

Confusing terminology

The questions that people mainly worry about, are:

  • Are they are getting enough nutrients through their food;
  • if there is any need for supplementation; and
  • whether they are likely to face harm by taking excess nutrients?

On top of this, there is much confusion with conflicting research papers, constantly shifting goals, and various acronyms such as RDA, DV, AI, and RDIs. This is a good recipe for your freezing into inaction. Let us simplify some of this.


To standardise matters, the Institute of Medicine at the National Academy of Sciences, USA recommends intake levels of common nutrients based on RDAs (Recommended Dietary Allowances). There are different numbers for each nutrient for different age groups, genders, and even life stages (such as pregnancy).


Sometimes, you cannot measure what is adequate and what is not, without doing long–duration experiments. Such trials will border on being unethical: how can you knowingly let some people be deprived of a nutrient till they develop health problems?

So, when there are no established RDAs, there are AI (Adequate Intake) levels.


Using these numbers, the U.S. Food and Drug Administration (FDA) fixes a number called Daily Value or DV. This is a single number for each nutrient’s requirement. It is a legal requirement to mention DV of each nutrient on all the food and supplement bottles.

Unfortunately, the daily requirements of different age groups cannot be combined into such a single number. So DV uses the most common number: that for a young adult.

Thus, before using a DV written on a bottle blindly, think if you are a young adult. If you a senior citizen, or a person with special requirements, find out more from the internet, or talk to your doctor.

Changing numbers

On top of all this, various organisations change their recommended numbers, based on new data. Since the numbers are based on studies of environmental issues, crops, lifestyles, food patterns, and dietary habits, the older numbers refer to earlier generations of people and their requirements. As the data from new sets of people is gathered, some of these numbers are bound to change.

Of course, human beings don’t change over a generation. So, what was adequate potassium for your grandfather should still be adequate potassium for you.

However, you are consuming far more sodium than your grandfather did, since the modern, processed foods have much higher salt content than the natural fruits and vegetables that your grandfather ate. So, the new guidelines for potassium consumption are 50% more than the earlier recommendations.

Cutoff levels

Note that these recommended dietary nutrient levels are not some kind of sharp cutoff levels.

For example, vitamin K is needed for blood clotting. The deficiency of vitamin K can lead to unchecked bleeding and haemorrhage. The RDA for vitamin K is 80 μg. But, if you consumed 79 μg a day, your blood would not suddenly stop clotting properly and you would not haemorrhage to death. Similarly, consuming 81 μg a day would not ensure that you would never get clotting problems.

How are the cutoff decided

The way these numbers are derived is by plotting the incidence of problem on Y–axis (vertical axis) and the nutrient intake on the X–axis or horizontal axis. The plot shows how the incidence of problem changes with the amount of nutrient taken.

Usually, such a graph showing dependence on nutrient is a continuum. There is no abrupt change or inflection point at certain nutrient intake level.

An expert committee looks at such charts, obtained from various trials. They pour over this data and decide an intake level as a point where the incidence of problem becomes unacceptably high.

Of course, life is never so straight–forward. So, these numbers are approximations and interpretations by experts. While they are not arbitrary, you don’t have to rely on them as absolute cutoffs, such as passing marks in an examination.

Expert committee compulsions

If you think the cutoff levels are decided purely based on medical data, well, think again.

Without going into any conspiracy theory, remember that the expert committees also want to reduce expenses incurred by people on unnecessarily increasing a nutrient intake, either through food or supplements. So they look for the absolute minimal level of consumption that the society, as a whole, can get away with. Quite often, this means poorer countries will have lower RDAs than developed nations.

Government compulsions

Very rarely, the decisions are also political and economic. For example, increasing the cutoff level for vitamin C, would suddenly make a much larger percentage of population vitamin C–deficient. While nothing changed in those people’s health, they got slotted into deficient category from normal category.

Many governments have to allocate budgets for health of its citizens. If a larger number of people become deficient (on paper, suddenly), due to the changed goalposts, the government has to earmark much higher budget to eradicate, or reduce, that deficiency in its population.

The government may have to provide free nutrient supply for underprivileged or at–risk populations, such as young school children. Or they may have to change the rules, enforcing food companies to fortify some foods. Add to this the cost of redoing every single product label in the country, to reflect the changes. As a result, some governments don’t increase their RDA numbers, unless absolutely unnecessary.

Optimal health levels

In light of these facts, I personally feel that RDAs are incorrect numbers to focus on. Most individuals, especially if they are well–to–do, should look at much higher numbers, for optimal, or at least better, health.

Preventing illness or maintaining wellness

The entire procedure outlined above should tell you that RDAs are not meant to be numbers that keep you healthy. RDAs are levels below which you have a high chance of developing medical disorder or illness. So, they are not guidelines for maintaining health; they are guidelines for preventing illness. Do you advise getting just passing marks to your children, or do you ask them to excel? Then, why would you focus on just scraping through your nutrient requirement?


Another reason for considering far above the RDA levels is the data has scatter. When it comes to passing marks, there is no scatter. For example, if one is considered to have passed the examination on obtaining 35% marks, then getting 34.5% is a fail grade and 35.5% is a pass grade.

However, given that the RDA cutoffs are for people “on an average”, it is quite likely that someone who consumes more than the RDA level has less than adequate intake. After all, any average is made up by values above and below the average. If you happen to be a person whose health needs a higher level of nutrient cutoff, perhaps due to slightly worse family history, you will face problem in the long–term if you consume just the RDA level of the nutrient.

Upper tolerable intake levels (UL)

How high can you go without causing harm to yourself, especially if you can financially afford the nutrient consumption?

The guidelines mention ULs (Upper Tolerable Intake Levels), a sort of upper limit to how much one can consume ‘on a daily basis’ before any harm may be caused.

Note that UL is not necessarily the quantity that causes toxicity, if consumed at one go. UL is the level that causes harm after prolonged daily consumption; toxicity is the level that causes harm after single ingestion.

In my opinion, as long as you are not crossing ULs of your nutrient, you are fine. There are only a handful of nutrients, such as calcium, where the UL is quite close to the RDA levels (given in a table below). For calcium, the UL is only 1.6 times the RDA. So you are advised to stay closer to RDA levels for calcium.

And if that raises your eyebrows, note that UL multiple for sodium is still lower, 1.5 times the RDA. And it is so low that almost everyone that you and I know is exceeding that level on a daily basis. We are still standing, right?

Nutrients work together

Unlike pharmaceutical drugs, many nutrients work together. For example, if your intake of vitamin D is inadequate, your body will not be able to get sufficient calcium even if you consume recommended amounts of it.

Also, some nutrients compete with one another. So if you take too much magnesium along with calcium, your body will not be able to absorb sufficient amount of calcium, in spite of consuming enough of it.

Read a very comprehensive article on this website: Nutrients that work together.

For the abovementioned reasons, the optimum levels of nutrient intake should be significantly above the respective RDAs or DVs.

New DVs

The US FDA did not change its DVs from 1968 to 2016, in spite of new RDAs coming out regularly. Finally, in July 2016, it issued new DVs. Here is the summary of the changes.

RDA and UL table

The Institute of Medicine guidelines for nutrient RDA and RDI are far more comprehensive. For example, the recommended number for natural vitamin E is different from that for synthetic vitamin E.

Table 1 below gives this summary, along with the Indian RDA levels, which are often different than the US RDAs.

The last column shows how many times the UL, or the highest advisable daily intake, is of the US RDA, or the minimum advisable daily intake, for the nutrient. For example, one should have 400 μg of vitamin B–9 or folates (almost similar to folic acid but slightly different) a day. However, consuming above 1000 μg a day is not safe. It is fine for a day or a few days, but consistent daily consumption above that level is not advisable.

For some reason, the vitamin B–9 number for India is 200 μg, which is probably too low.

Now, if you feel you have mastered all this, have a look at the magnesium row in the table. Its daily recommended minimum intake is 420 mg and the daily recommended maximum intake is 350 mg. Go figure yourself, or read this article.

Table 1. Recommended daily intake (RDI) of various nutrients
NutrientOld RDI USANew RDI USA (M)New RDI USA (F)India RDAUpper Limit (UL)UL/RDI (M)
Vitamin A900 μg900 μg700 μg1000 μg (M);
840 µg (F)
3000 μg3.3
Vitamin B11.5 mg1.2 mg1.1 mg1.4 mgUnknown 
Vitamin B21.7 mg1.3 mg1.1 mg1.6 mgUnknown 
Vitamin B320 mg16 mg14 mg18 mg35 mg2.2
Vitamin B510 mg5 mg5 mg-Unknown 
Vitamin B62 mg1.7 mg1.3 mg2 mg100 mg58.8
Vitamin B7300 μg30 μg30 μg-Unknown 
Vitamin B9400 μg400 μg400 μg200 μg1000 μg2.5
Vitamin B126 μg2.5 μg2.4 μg1 μgUnknown 
Vitamin C60 mg90 mg75 mg80 mg (M);
65 mg (F)
2000 mg22.2
Vitamin D400 IU (10 μg)20 μg15 μg15 μg100 μg5
Vitamin E30 IU (20 mg)15 mg15 mg10 mg1000 mg66.7
Vitamin K80 μg120 μg90 μg55 μgUnknown 
Calcium1000 mg1300 mg1300 mg1000 mg2500 mg1.9
2.3 g2.3 g-3.6 g1.6
Choline-550 mg425 mg-3500 mg6.4
Chromium120 μg35 μg25 μg33 μgUnknown 
Copper2000 μg900 μg900 μg2000 μg10000 μg11.1
Fluoride-4 mg3 mg-10 mg2.5
Iodine150 μg150 μg150 μg150 μg1100 μg7.3
Iron18 mg8 mg18 mg19 mg (M);
29 mg (F)
45 mg5.6
Magnesium400 mg420 mg310 mg300 mg350 mg0.8
Manganese2 mg2.3 mg1.8 mg2 mg11 mg4.8
Molybdenum75 μg45 μg45 μg-2000 μg44.4
Phosphorus1000 mg1250 mg700 mg600 mg4000 mg3.2
Potassium3.5 g4.7 g4.7 g-Unknown 
Selenium70 μg55 μg55 μg40 μg400 μg7.3
Sodium-1.5 g1.5 g-2.3 g1.5
Zinc15 mg11 mg8 mg17 mg (M);
13.2 mg (F)
40 mg3.6

Image credit: Conor Alexander, CC BY-SA 4.0
First published on: 6th November 2018
Latest Update on: 10th March 2023


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