Karen Collins, MS, RD, CDN
Recent studies have sparked debate over whether or not garlic can help lower cholesterol. While that discussion rages back and forth, another set of findings about garlic's health benefits tends to get overlooked.
Mounting evidence suggests that garlic in the diet is consistently linked to lower risk for cancer. In one of the latest studies on this topic, less than a clove of garlic a day was enough to cut men's risk of prostate cancer in half compared to men who ate none.
Garlic's link with lower cancer risk has been well established in highly focused laboratory studies involving cells and animals, as well as in studies that look at large human populations. Yet because people who eat more garlic also tend to eat more vegetables and engage in other healthy eating habits, it has not always been clear how much of garlic eaters' lower cancer risk is due to garlic per se.
More recent studies, including this new study on prostate cancer, have tried to account for this by statistically controlling for such associations, and garlic is still coming up a winner.
And it's not just prostate cancer. Studies also tie garlic consumption to the prevention of colon, stomach and possibly breast cancers. One of the most prominent garlic researchers, John Milner, Ph.D., now with the National Cancer Institute, notes that the benefits of garlic are not limited to a specific tissue, which suggests that garlic probably has broad anti-cancer effects throughout the body.
One key question about garlic's potential is whether we get the greatest benefit from garlic as a food or as a supplement. Several specific compounds in garlic have been isolated and are currently under investigation. The results from studies involving garlic that has been processed into supplements, however, have been inconsistent.
This may be due to the wide variations that exist between different garlic products. It's also possible that the many different compounds in garlic offer the best protection when they occur in whole garlic, where they can interact with each other in complex ways we do not yet understand.
Sometimes people turn to supplements because they think that large amounts of garlic are required to attain benefits, but this does not seem to be the case. Milner has reported benefits with the equivalent of one or two cloves of garlic a week; other researchers suggest that four or five cloves a week may be more ideal. In fact, loading up with large amounts of garlic every day increases the risk of digestive problems.
Another misconception is that garlic must be consumed raw to be beneficial. It is true that when garlic is cooked immediately after peeling, certain enzymes are inactivated and cancer-fighting benefits are lost. But if you peel the garlic, let it rest 15 minutes (while you chop the other ingredients) and then cook it, the full benefits remain.
For those who aren't garlic lovers, the good news is that the entire garlic and onion family contains cancer-fighting compounds. In the latest study on prostate cancer risk, higher total consumption of vegetables in the onion-garlic family was linked with almost 50 percent lower risk of prostate cancer. Studies have shown that while garlic, onions, scallions and leeks contain slightly different compounds, the substances that block cancer-promoting enzymes, promote DNA repair and regulate the cell life cycle are found in all these foods.
According to the American Institute for Cancer Research (AICR), vegetables, fruits, whole grains and beans all provide valuable nutrients and natural phytochemicals with a variety of cancer prevention benefits, so just adding garlic or onions to an otherwise poor diet is not the answer to good health. But if you have ever thought that healthy eating was bland and flavorless, these studies - which show that the most pungent and aromatic vegetables have a place at a healthy table - clearly put an end to that idea.