100% of RDAs is too much of a good thing, Danish researchers warn

By Annie Harrison-Dunn

- Last updated on GMT

'So should they take the risk and maybe poison everyone? Because very few groups have inadequate intakes,' says Danish researcher. © iStock.com / Photobuay
'So should they take the risk and maybe poison everyone? Because very few groups have inadequate intakes,' says Danish researcher. © iStock.com / Photobuay

Related tags Vitamin

Supplement manufacturers should not be offering 100% of recommended dietary allowances (RDA) in vitamin and mineral supplements, Danish research highlighting the risk of overdose has warned.

A survey of nearly 4000 people conducted by the National Food Institute at the Technical University of Denmark (DTU) found six out of 10 Danes take at least one vitamin or mineral supplement despite them getting enough from their diet alone.

The researchers urged consumers to buy supplements that contained less than 100% of RDAs to avoid the risk of overdosing on certain micronutrients.

But how easy is this when almost all of the 455 different supplements taken by the participants boasted this maximum dose?

Senior researcher at the institute Anja Biltoft-Jensen told us manufacturers should change products to offer no more than 50% of the RDAs.

“I think it should be lowered to only half of the dose – because it’s only a supplement, it’s not supposed to provide the whole amount.”

The health risks

"It is not that people drop dead if they take a dietary supplement, but adverse health affects will occur after intake of high doses above the upper level during a longer period,"​ Biltoft-Jensen said. 

Too much retinol may cause liver damage whereas too much vitamin D may lead to more calcium than can be excreted. 

Taking high doses of zinc reduces the amount of copper the body can absorb, which may lead to anaemia and weakening of the bones.

She said while manufacturers were not aiming to offer products that could harm consumers, the issue did come down to their desire to sell products.

For this reason regulatory action may be needed, be it at a national or EU level.

Health-conscious consumers saw supplements as a way to boost intakes - without considering possible risks of exceeding upper tolerable limits. 

"We didn’t ask why people were taking supplements but I think it’s because it’s an everyday routine and because I think people want to feel on the safe side. Interestingly it is the adults who have the healthiest diets that take the supplements.” 

Much too much, much too young

The survey showed through the diet alone 30% of four to ten year olds exceeded intake limits for the vitamin A retinol and 73% for zinc.

When supplements were added into the equation the rate of four to six year olds exceeding the upper tolerable limits rose to 43% for retinol, 45% for iron and 73% for zinc.

Among supplement users aged seven to ten and 11 to 14, the limits for zinc were exceeded by 46 and 25%, respectively. For retinol this was exceeded by 21 and 10%, respectively.

The institute said only a few groups of the population actually needed to be supplemented.

Women of child bearing age were at particular risk of iron deficiency and vitamin D was an issue for the whole population.  

“The majority of Danes do not need to take a supplement as a healthy and balanced diet and thoughtful sun exposure are the best ways to meet the need for most vitamins and minerals. If people still want to take a supplement they should choose them wisely,”​ Biltoft-Jensen said in a release.

The survey shows 62% of 11-17-year-olds and 34% of adults in Denmark have a “very high probability”​ of inadequate vitamin D intakes from their diet.

Even among supplement users, 35% of 11-17-year-olds and 26% of 18-50-year-olds had a risk of inadequate vitamin D intake.

For iron, 79% of 14-17-year-old girls and 53% of 18-50-year-old women were below recommendations.

Supplementing subgroups – poisoning the masses?

But these were subgroups, Biltoft-Jensen said, and this did not warrant supplementation on a mass scale.

“Other groups like teenagers also have low intakes of other nutrients, but the question is if everyone taking a supplement should be endangered with very high total intakes for several vitamins and minerals? Because very few groups have inadequate intakes.”

She said fortification may be warranted in cases where clinical signs of deficiency were clear, such as iodine, but this had to be evaluated on a case-by-case basis. 

“Fortification can make it very difficult for people to know how much they are consuming.”

Denmark’s only mandatory fortification scheme is for iodine in salt. For micronutrients like vitamin D this was less clear cut, she said. 

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RDA and Danish Researchers

Posted by Nigel,

what a poor quality article. RDA are based on decades old work that was questionable even back then. RDA are designed to prevent deficiency and do nothing address insufficiency ie what is the optimal, but then as far as I know nobody has ever bothered to do that work. Shame to see such a poor article that can only add to the confusion that the average consumer must face

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Posted by David,

It is regrettable that 'research' of this calibre gets used by the bureaucrats in Brussels to micro-regulate our lives.
I would have hoped for something better from Danish researchers.
As already pointed out by ARTICLE + FLUFF post below, RDA is now obsolete. It has been superceded by the DRI, see:
DRI includes,Tolerable Upper Intake Level (UL): maximum daily intake unlikely to cause adverse health effects.

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Posted by L.Lee coyne,

The article is FLUFF!! Nobody is dieing from excess supplementation. RDA's. - a term no longer in use in the USA, is an estimate of minimums, not optimums. http://suppversity.blogspot.ca/search?q=vitamin+deficiencies, http://www.crnusa.org/whatsnew/?p=1559

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