Both BHA and BHT protect fats from oxidation, which is damage due to exposure of the fats to oxygen. In fact, they work in a similar way as vitamin E. BHA and BHT are often added to potato flakes, dry breakfast cereals, enriched rice, and foods containing animal fats and shortening.
The United States Food and Drug Administration (FDA) considers both BHA and BHT to be safe. Researchers estimate the typical intake of BHA has no dangerous effects, and it would take at least 125 times the usual amount to become toxic. BHT is also considered to be safe; however large amounts of BHT may have some interactions with hormonal birth control methods or steroid hormones, and may increase levels of liver enzymes. Currently the FDA allows food manufacturers to use BHT, however additional safety studies are suggested.
Butylated Hydroxyanisole (BHA). Accessed August 17, 2009. http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigation.cfm?rpt=scogsListing&id=40
Butylated Hydroxytoluene (BHT). Accessed August 17, 2009. http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigation.cfm?rpt=scogsListing&id=41
Butylated Hydroxytoluene, BHT. Accessed August 17, 2009. http://food.oregonstate.edu/glossary/b/butylatedhydroxytoluene.html