People have long studied garlic for its health benefits and now, a new study looks at the research linking garlic consumption to reducing cancer risk.

The analysis on garlic, published in the American Journal of Clinical Nutrition, asks whether there is enough data to support a health claim on food labels linking garlic consumption to reducing cancer risk. The bottom line: no. Although garlic may play a role in cancer prevention, more studies are needed to draw conclusions.

In order for labels to state health claims, the U.S. Food and Drug Administration requires that the claims be supported by human studies. This new analysis looked only at human studies, although there are many laboratory studies suggesting a potential role for garlic in cancer prevention.

The researchers started with 183 human studies on garlic and cancer risk. After removing the studies that did not meet the researchers’ criteria, they were left with 19 studies covering 10 types of cancer.

These studies include some in which people merely labeled their garlic consumption as none, low, medium or high, with no clear definition of the terms. When the terms were defined, “high” garlic use might mean consuming garlic twice a month in one study and four cloves a week in another.

Knowing how much garlic people eat is only part of the research challenge. Studies have shown that it takes 10 to 15 minutes after raw garlic is chopped or chewed for garlic’s inactive compounds to convert into the active, protective forms. People who cook garlic immediately after chopping it probably don’t get the same benefits as those eating the same amount of garlic raw or cooked after a 10- to 15-minute wait.

The American Institute for Cancer Research (AICR) 2007 expert report on diet and cancer risk, which includes analysis of human studies, concluded that garlic probably protects against colorectal cancer. Also, garlic is part of the allium family (along with onions and related vegetables) and allium foods probably protect against stomach cancer.

The AICR report noted that the findings of individual studies could be blurred by the difficulty in detecting true consumption of garlic and its active compounds. Yet together, the trend suggests that garlic’s impact may be real.

As part of an overall strategy of healthy living to lower cancer risk through weight control, regular physical activity, and a balanced, mostly plant-based diet, garlic does not deserve top billing. But with all we are learning about how plant foods work together to produce more benefit than they do individually, adding garlic to your foods can add flavorful seasoning and, possibly, some protection against cancer development.
References:
1. American Institute for Cancer Research.
2. Image by Nino Barbieri.