Quoted from The Hundred Year Lie:

At least five thousand years ago the stinky white bulb we call garlic was being pounded into medicinal foods to ward off illness and disease. One builder of an Egyptian pyramid even carved into the monument an account of how much garlic his work crews consumed to stay healthy.

As one of humanity’s earliest healers, garlic was prized because it produced noticeable effects in strengthening immunity. It was no coincidence that in Dracula legend and lore the cloves of garlic provided immunity against the vampire’s attempts to drain a person’s lifeblood.

We have rediscovered this ancient wisdom about garlic in modern laboratory settings. Over the past few decades about one thousand science articles have appeared touting the medicinal properties of this pungent root. Garlic contains up to two hundred compounds and active ingredients, including selenium, sulfur compounds, potassium, phosphorus, amino acids, vitamins B and C, copper, and zinc. While there is evidence for the health effects of single ingredients, what makes garlic so potent for overall human health is the synergistic effect of all these natural chemicals working together.

At the molecular level, experiments have demonstrated specific ways that garlic activates the immune system. “[Our findings] do substantiate that garlic widens blood vessels and reduces hypertension,” observed the leader of one experiment, David Julius, a professor in the department of cellular and molecular pharmacology at the University of California at San Francisco.

Other scientists have shown how allicin, a substance garlic excretes when squeezed, is a natural antibiotic that kills bacteria and intestinal parasites. Experiments on laboratory animals at Pennsylvania State University discovered how garlic powder protects against breast cancer, while physicians at UCLA uncovered evidence that garlic stops a variety of cancers from growing. Studies in Annals of Internal Medicine (1993) and the Journal of Physiology and Pharmacology (1979) both found persuasive evidence that garlic significantly decreases cholesterol levels in most people.

Fitzgerald, Randall. The Hundred-Year Lie: How to Protect Yourself from the Chemicals That Are Destroying Your Health (p. 182). Plume. Kindle Edition.