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.”
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.