Such a level of certain forms of vitamin A are potentially toxic, according to Consumerlab.com, the third party analyst that carried out the test.
Three other products came in between 68.2 and 77.5 percent of their stated vitamin A label claim.
Six other products were voluntarily submitted by their manufacturers – all passed along with a further three that were deemed to be substantially the same as products tested.
“Tests of one cod liver oil supplement showed it to contain 7818 IU of vitamin A as retinyl palmitate, nearly double its claimed amount of 4000 IU per teaspoon,” Consumerlab wrote, noting that recommendations existed that pregnant women, for instance should not exceed 5000 IU per day to avoid birth defect risks.
The Institute of Medicine (IOM) has established a level of 5666 IU for children of 13 years, less for those that are younger.
Under and over
While vitamin A has eye health and immunity benefits and is important in warding off some cancers, overdosing on vitamin A forms such as retinyl palmitate (also known as pre-formed vitamin A) can lead to bone and liver abnormalities, as well as birth defects of the brain, eyes and head.
Beta-carotene, or pro-vitamin A, is not capable of such toxic potential.
Vitamin A deficiency can cause night blindness and reduce immunity and is more common in the developing world than the developed world.
Brands tested included Country Life, Ethical Nutrients, Garden of Life, Health from the Sea, Metagenics, Nature Made, Nature’s Bounty, Nature’s Way, Puritan’s Pride, Rite Aid, Solgar, Source Naturals, Spectrum Essentials, Swanson, Vitamin Shoppe, and Vitamin World.
Neither the FDA nor any other federal or state agency routinely tests supplements for quality prior to sale.
Products made from fish liver oil were also tested for possible contamination with mercury and PCBs. All non-chewable and non-time-release tablets or caplets were tested for their ability to break apart properly to release their ingredients.