NRC report urges improved regulation of animal dietary supplements

WASHINGTON — Regulation of animal dietary supplements is in "disarray," according to new report from the National Research Council (NRC).

The report, requested by the Food and Drug Administration's Center for Veterinary Medicine, says the growing use of such supplements has raised several concerns, including the safety of specific supplements and the approaches taken to determine their safeness.

The NRC panel that authored the report says clear and precise regulations are needed. An improved adverse-event reporting system for supplements would help, it says. Deficiencies cited in existing systems include limited public access, passive rather than active solicitation of adverse events and unclear determination of minor vs. serious adverse events.

The report also assesses whether the addition of three dietary supplements — lutein, evening primrose oil, and garlic — to the diets of horses, dogs or cats may cause significant adverse health effects.

The authors conclude that because of inadequate data they cannot clearly define a safe upper limit for any of the three, but can cite historical safe intakes (HSI) and estimate presumed safe intakes (PSI) based on available research.

Additionally, the "generally recognized as safe" designation used for both human and animal ingredients is helpful in determining safe intake levels, but safety in humans does not guarantee safety in animals, the committee noted. For example, excess garlic intake can cause hemolytic anemia in horses, dogs, and cats, but this adverse effect has not been reported in humans.

The Association of American Feed Control Officials sanctions the ingredients used in animal feeds, but does not dictate minimum or maximum amounts of nutrients allowed.

The daily PSI and HSI, given in milligrams per kilogram of body weight (mg/kg BW), determined by the committee for the three dietary supplements are:

Lutein

» For horses, the PSI is 8.3 mg/kg BW when obtained from forage or natural sources; no data exist on supplements.

» For dogs, the PSI is 1.8 mg/kg BW, with an HSI of 0.45 mg/kg BW.

» For cats, the PSI is 7.2 mg/kg BW, with an HSI of 0.85 mg/kg BW.

Evening primrose oil

» For horses, the PSI is 400 mg/kg BW, which assumes the intake of total fat will not exceed 23 percent of the diet.

» For dogs, the PSI is 424 mg/kg BW, which is the upper level used in clinical trials. Most likely the upper safe intake is higher than this.

» For cats, the PSI is 391 mg/kg BW. It is likely cats could tolerate higher levels.

Garlic

» For horses, the PSI is 90 mg/kg BW, with an HSI of 15 mg/kg BW.

» For dogs, the PSI is 56 mg/kg BW; garlic has a long history of safe use as a supplement, with mean levels of 22 mg/kg BW being reported without serious adverse events.

» For cats, there are insufficient data to support a generic recommendation that covers all garlic preparation types. Mean intake levels of 17 mg/kg BW have been reported with apparently no serious adverse events.