Gut-level control of aflatoxin.

Gut-level control of aflatoxin

Low levels of aflatoxin -- the most potent natural carcinogen -- contaminate many foods. Though it would be virtually impossible to eliminate all dietary sources of this toxin, produced by molds growing on grains and peanuts, there are nonbinding federal "action levels" suggesting limits on its concentrations in food and feed products. To avoid exceeding the action level of 0.5 parts per billion (ppb) for milk, farmers today must feed their dairy cows grains tainted with no more than 20 ppb of the toxin -- which flourished after last year's drought and late-season rains. In the future, however, farmers may salvage more heavily tainted grains for dairy feed.

Veterinary toxicologist Roger B. Harvey and his colleagues at the Agriculture Department's Mycotoxin Research Lab in College Station, Tex., find an off-the-shelf additive -- now used as an inert and nondigestible anticaking ingredient in feeds -- binds aflatoxin in the bovine gut, dramatically reducing its levels in milk. When used as a 1-percent additive in heavily contaminated (100-ppb) cattle feed, hydrated sodium calcium aluminosilicate reduced aflatoxin in milk to between 0.27 and 0.65 ppb -- levels 54 to 60 percent lower than those in the milk of animals fed untreated, comparably tainted grain.

Ironically, even though the aluminosilicate is an approved feed additive, farmers cannot legally use it to reduce aflatoxin levels until it gains formal Food and Drug Administration approval for this specific purpose. Harvey says the additive's manufacturer is considering seeking such approval.