People hoping to fight infections with garlic may have to stick with fresh, crushed garlic. Health writer Jennifer Garfinkel explains that garlic's antibacterial effects come from allicin, "a chemical compound that's released when cloves are chopped or crushed." If allicin's chemical properties are altered when rendering garlic into powder, the antiviral power is compromised.

On the Other: Powdered Garlic May Offer Antiviral Allicin Too

Those who find garlic powder a more palatable option may be in luck. According to Peter Josling, director of the Garlic Centre in East Sussex, while aged garlic and garlic oil will lose their allicin potential in the manufacturing process, such is not the case with garlic powder. Powdered garlic that offers allicin will be antiviral too.

Bottom Line

While not every garlic form is the same, fresh and powder are close. David Schardt and Bobbie Liebman, associate nutritionist and director of nutrition respectively for the Center for Science in the Public Interest, tested supplements to see how many micrograms of allicin each supplied. They found that fresh garlic is the best choice; powder definitively came in second. A third of a teaspoon offers 5,000 mcg, the amount in one large clove.

Source:

Psychology Today, "Beware, Vampires and Viruses," Jennifer Garfinkel, October 2007

Allicin from Fresh Garlic: Nature's Original Microbial," Peter Josling

Nutrition Action Health Letter, "Powder Wise ... Pill Foolish," David Schardt and Bonnie Lieberman, Jul/Aug 1995