One of the most frequently asked questions in health food shops is “Why does this vitamin have more than 100% of the NRV? Isn’t that dangerous?” The short answer is, definitely not.
This guide explains the terms you will see to describe nutrient levels in supplements and foods, including RDA, NRV, DRV, Upper Level and Supplementary Rate. We’ll help you decipher labels, so you can make informed choices of supplements and foods.
Recommended Dietary Allowance (RDA): What’s the bare minimum to stay healthy?
This term was first coined by the US Food and Nutrition Board in the 1940s, primarily with the aim of keeping American soldiers healthy in the Second World War. Before the war, visible nutritional deficiency diseases and malnutrition were common in the USA and Europe. When food shortages led to millions of people dying of starvation across Europe and Asia, nutrition became a vital element of keeping soldiers healthy enough for active service.
The term RDA was soon adopted by the World Health Organisation (WHO) and became the global benchmark.
It is defined as the minimum amount of a nutrient that the average healthy person needs each day, in order to avoid developing a deficiency disease. There are different levels for ages and sexes.
If we break that down, several things become clear:
- This is a minimum, not a maximum.
- It applies to healthy people: during times of illness, we may need higher amounts of many nutrients.
- It applies to the average person, but not everyone is average: for some people this amount will be more than necessary and for others (estimated to be 2.5% of the population at the time RDA levels were set) it will not be enough.
- It is the amount needed to prevent deficiency diseases like scurvy, beriberi or rickets, not the amount that can make someone as healthy as possible.
Are RDA levels too low?
Many criticisms have been levelled at RDA figures. They are often said to be too low. The RDA for most nutrients was based on very limited research with gaps filled in by the opinions of deciding committees. It has been pointed out many times that this is the very lowest rank in the quality of evidence pyramid, that is, opinion. The highest level of evidence would be randomised controlled clinical trials.
After such trials took place for vitamin D and calcium in 2011, the RDA for both nutrients was increased significantly. The RDA for Vitamin D went up by 300% for younger adults!
- The RDA was originally 200 IU for younger adults and it is now 600 IU of Vitamin D.
- The RDA for older adults was 400 IU and it is now also 600 IU of Vitamin D.
- The RDA for people over 70 was 600 IU and it is now 800 IU of Vitamin D.
Nutrient Reference Value (NRV): How much is in this food?
By the 1980s, the EEC (now the European Union) wanted a standard way to label foods with nutritional content. The term NRV was proposed in 1988 and finally approved by the EU in 2014, after 26 years of consultations between the European Food Safety Authority (EFSA) and the WHO. At this point, NRV replaced RDA on food and supplement labels.
The Nutrient Reference Value (NRV) amount for each nutrient is identical to the RDA amount. The Nutrient Reference Value is used on labels for foods and nutritional supplements.
The amount of each micronutrient (vitamins and minerals) and macronutrients (protein, fat and carbohydrate) that the product contains is stated as a percentage of the NRV.
The UK has continued to follow the EU standards since Brexit and is unlikely to change, since this system is used globally and guided by the WHO.
Dietary Reference Value (DRV): How much should you be eating?
Dietary Reference Values (DRV) is the system used by the UK Department of Health to advise the public. The same system is used in the EU, but the numbers are set by each nation individually. This is because the national diet and climate has a major impact.
The Dietary Reference Value is the ideal amount of each nutrient you should eat each day in your diet. It’s used for vitamins and minerals, and also the macronutrients protein, carbohydrates and fat.
For example, people in the Mediterranean get a lot of their vitamin D from sunshine whereas people in northern countries depend more heavily on vitamin D from the foods they eat. This means their Dietary Reference Value needs to be higher.
There are also variations between different groups of the population, such as the elderly who generally absorb nutrients less well, and children who tend to use lots of energy and also have different needs as they are growing rapidly in size.
Upper Level (UL) or Tolerable Upper Intake Level: What’s the highest dose you can safely take?
In 2000, with the nutritional supplements market well established and some people getting carried away, it was decided that safe upper limits of nutrients should be defined.
The Upper Level is the highest amount of a nutrient that can be safely consumed every day over the long term, without causing side effects for 97.5% of the population.
This implies that it would be too much for 2.5% of the population. As with the RDA and NRV, this level is specific to age groups and defined by sex. The European Union sets its levels differently from the USA for some nutrients. For example, the adult UL for zinc is 40 mg in the USA but only 25 mg in the EU.
You do not need to worry about the UL of nutrients unless you habitually take supplements of vitamins and minerals above the amount stated on the label, or if you have certain medical conditions such as liver disease. The UL is generally more important for minerals and fat-soluble vitamins (Vitamins A, D, E and K) than for water-soluble vitamins, as the body can more easily flush out excess amounts of these.
You can find tables of the Upper Level of each nutrient here:
Dietary Reference Intake (Wikipedia)
Supplementary Rate: What’s the ideal dose for your supplement?
This is not an official term, but has been coined by some writers on nutrition to describe typical doses of nutrients seen in supplements.
The Supplementary Rate is the typical dose range of a nutrient that is seen in supplements.
Supplementary rates are often much higher than the RDA or NRV, because supplements are intended for people who need more than the usual amounts of nutrients.
As a typical example, many people take vitamin C supplements when they have a cold. If you remember that the definition of the RDA is the minimum amount required by a healthy person to avoid getting scurvy from a vitamin C deficiency, it stands to reason that someone ill with a cold may need more than this. The RDA for vitamin C is 90mg a day for men and 75mg a day for women, yet the typical supplementary rate that you will see on most vitamin C supplements is 1000mg, more than 10 times this amount. To give a yardstick on this, you can get the RDA of vitamin C from one and a half oranges. To get the common supplementary rate, which research suggests your body will use when fighting off a cold, you would need to eat about 20 oranges.
There is no official list of “supplementary rates” and they are not regulated by legislation or guidelines. They are typically chosen by dieticians relying on the scattered available research and received wisdom, choosing safe amounts between the RDA minimum and the UL maximum.
Conclusion
If you do take nutritional supplements, the simple rule is to follow the dosing amount on the label. If you take more than one supplement, pay attention to overlap. For example, if you take a multivitamin and a separate magnesium supplement, double check the total amount of magnesium you’re getting from all your supplements together.
