The study was announced in the latter part of last year in papers presented at the Japan Health Medicine Association on November 12, and at the Japan Society for Medican Use of Functional Foods on December 3.
It has now been published online, ahead of appearing in a forthcoming issue of Regulatory Toxicology and Pharmacology.
The study, conducted by Ikematsu et al at the Department of Clinical Research of Haradoi Hospital, was double-blind, randomized, placebo-controlled in design. Over a four week period eight-eight adult participants took a daily Kaneka Q10 capsule in one of three doses: 300, 600, and 900mgl.
The researchers observed no serious adverse events in any group. Such adverse effects as were reported - most commonly cold symptoms and gastrointestinal effects - were not dose dependent and were deemed to have no relationship to the intervention. Moreover, and any changes in hematology, blood biochemistry, and urinalysis were not seen to be dose-related and were judged not to be clinically significant.
The plasma CoQ10 concentration after 8-month withdrawal was almost the same as that before administration.
"These findings showed that Kaneka Q10 was well-tolerated and safe for healthy adults at intake of up to 900mg/day," wrote the researchers.
According to a company spokesperson, the study is the "ultimate confirmation of the safety of Kaneka Q10".
Kaneka began producing coenzyme Q10 in 1977, but until three years ago potent antioxidant was subject to pharmaceutical regulations in its home country of Japan. Since it was deregulated in 2003, there was a rush on supply leading to shortages around the world.
In 2002, the publication of a study indicating that CoQ10 may help slow the progression of Parkinson's disease confounded the situation.
The supply issues have since been eased, partly through Kaneka's own production expansion: last month it started shipping from its new facility in Japan. Its Taksago plant now has an annual production of 180 metric tons.
The company is also expanding in the US, thought to account for up to two thirds of global demand, with a new 100-ton plant under construction in Pasadena, Texas. Phase I construction has been affected by two recent hurricanes but is expected to be completed by the summer of 2006.
However there seems to be no let-up in launches of products containing CoQ10: a total of 260 dietary supplement and skin care products containing CoQ10 are listed in Mintels' GNPD as having launched in the United States between 2000 and September 2005 - and 75 per cent of these were dietary supplements.
However in Europe Mintel's database shows more use for CoQ10 in topical cosmetic products than in dietary supplements (25 percent of the total 157 products listed for the same period).
A spokesperson for Kaneka said the tendency to take higher doses of CoQ10 means it is "of the utmost importance" to use a safe and pure CoQ10.
Kaneka's product is produced through a yeast fermentation process which it says makes it purer and safer than others. Moreover, it is claimed to be identical to the body's own CoQ10, and be without the impurities sometimes found in synthetic versions.