Garlic fights nitrosamine formation ... as do tomatoes and other produce.

Nitrosamines and related toxic N-nitroso compounds induce cancer through the formation of adducts -- their tight chemical bonds to DNA. But at least in rats, adding high concentrations of garlic powder to the diet can greatly quash the formation of such adducts, according to nutritionists at Pennsylvania State University in University Park.

John A. Milner and his colleagues exposed their animals for 2 or 3 weeks to chemicals known to generate nitrosamines in the gut -- and subsequent liver or mammary cancers. Over the same period, some of the animals consumed large amounts of garlic: 2 to 4 percent of their diet by weight. The treated rodents didn't seem to object to the heavy seasoning, since they ate as much food as rats offered garlicfree chow.

The big difference appeared in the number of adducts the rats developed, Milner and his coworkers report in the Feb. 8 CARCINOGENESIS. Penn State's cuisine produced a drop of some 40 to more than 80 percent -- depending on the amount of garlic in the diet -- in the predominant liver adducts that form in animals administered the nitrosamine or nitrosamine precursors used in this experiment. Garlicky chow also produced a dose-dependent reduction of 55 to 69 percent in mammary adducts associated with another nitrosamine.

Milner's team suspects that some of garlic's anticancer benefits also stem from the ability of its organic sulfur compounds to break down and detoxify nitrosamines.

... as do tomatoes and other produce

Two years ago, Cornell University food scientists published data showing that eating green peppers, pineapples, carrots, strawberries -- and especially tomatoes -- can suppress the formation of nitrosamines in humans. Though these fruits and vegetables all contain vitamin C, which can derail the reaction that produces nitrosamines, the researchers began looking for additional blockers when they determined that each food's nitrosamine-inhibiting potency was greater than could be accounted for by its vitamin C alone.

In the January AGRICULTURAL AND FOOD CHEMISTRY, Cornell's Michael A. Helser and Joseph H. Hotchkiss now identify two new nitrosamine blockers -- p-coumaric and chlorogenic acids. Together, these phenols provide about 35 to 40 percent of a juiced tomato's nitrosamine-inhibiting activity. Though these compounds occur in many types of produce, green coffee beans constitute one of the richest sources of chlorogenic acids.

Overall, Helser and Hotchkiss find, the ascorbate (vitamin C) fraction of a tomato contains about half the fruit's nitrosamine-inhibiting activity. However, their data also suggest that because pure vitamin C appears to account for only about one-quarter of the inhibition associated with a tomato's ascorbate fraction, even the vitamin C portion appears to carry potent, as-yet-unmasked nitrosamine blockers.

These findings emphasize that people should rely on whole foods -- rather than a battery of vitamins -- to stay healthy. Hotchkiss concludes.