The Protein Works ignores call to lower Super Strength vitamin D3 levels

By Annie Harrison-Dunn

- Last updated on GMT

Dietitian and health writer Dr Carrie Ruxton first tweeted about the high dosage of The Protein Works' Vitamin D3 Super Strength tablets back in October.©
Dietitian and health writer Dr Carrie Ruxton first tweeted about the high dosage of The Protein Works' Vitamin D3 Super Strength tablets back in October.©

Related tags Vitamin d

UK supplement firm The Protein Works has dodged calls from a prominent dietitian to lower dosage of its Vitamin D3 Super Strength tablets, which offers 2500% of reference intakes.

The Vitamin D3 Super Strength tablets contained 5000 IU (125 microgrammes), a dosage that caught the eye of Scotland-based dietitian and health writer Dr Carrie Ruxton.

This dose tops the Tolerable Upper Intake Level​ of 4000 international units (100 microgrammes) set by the European Food Safety Authority (EFSA) for adults in 2012 and goes well over EFSA’s 15 microgrammes per day Adequate Intake​for adults published this year.

Co-founder of the company and head of marketing communications Ross Edgley replied in mid-October to Ruxton’s tweets and emails to say he “hugely appreciate[d] the feedback”.​ 

Yet since then Ruxton has received no further word on the company’s plans for the super strength product nor did the company respond to our requests for comment.

Ruxton told us supplement retailers had a duty to follow official guidance on safe upper levels, although EFSA's work has not yet been mandated on an EU level. 

“Having been contacted several times by me, The Protein Works was unwilling to explain their reasons for selling an excessively high dose supplement and could not offer any assurances that the stated dose was accurate,”​ she said.  

“This puts them in a bad light compared with others in the sector and should act as a warning to potential customers.”

Side lining potential side effects

On the product page the company poses the frequently asked question: What if any side effects will I get from taking vitamin D3 super strength 5000 IU tablets?”

The response reads: There are no known side effects with using vitamin D3.”


This clashes with official advice.

For example, the UK’s National Health Service tells adults – including pregnant and breastfeeding women, the elderly and children aged 11-17 years – that taking more than 100 microgramme (µg) of vitamin D a day could be harmful.

“Taking too many vitamin D supplements over a long period of time can cause more calcium to be absorbed by the body than can be excreted. This leads to high levels of calcium in the blood (hypercalcaemia),”​ it says on its public health advice website NHS Choices​. 

“Too much calcium in the blood can weaken the bones and damage the kidneys and the heart.” 

Conservative calculation? 

EFSA itself used hypercalcaemia as a marker of toxicity in its tolerable upper limit work.

However in its calculations EFSA noted that two studies in adults showed no adverse effects with a daily vitamin D dose of between 234 and 275 µg, which would be within the Super Strength tablet dosage. 

However it said there were uncertainties with this two-study value and instead settled on the more conservative 100 µg per day.

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Why just protein works

Posted by Josh,

Why just pick up on Protein Works, there are an abundance of brands creating 5000iu Vit D supplements.

I've been taking 10,000iu for 2 years now, nl levels all good.

Every persons needs is different.

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High Vit D3 intake

Posted by Coco,

its not a problem if you take K2 as well. Why you don't investigate this? Than you will find out that this combo brings the calcium to your bones, teeth. Where you need it.
I take 5000 since a few years and my nl level is 59, very good already. No side effects, just benefits. No flu, no cold, not sick since many years.

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