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Testing garlic’s cancer-fighting potential


April 13, 2010
By Fruit & Vegetable

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Researchers have designed a urine test that can simultaneously measure
the extent of a potential carcinogenic process and a marker of garlic
consumption in humans.

Researchers have designed a urine test that can simultaneously measure the extent of a potential carcinogenic process and a marker of garlic consumption in humans.

In a small pilot study, the test suggested that the more garlic people consumed, the lower the levels of the potential carcinogenic process were.

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“What we were after was developing a method where we could measure in urine two different compounds, one related to the risk for cancer, and the other, which indicates the extent of consumption of garlic,” said Earl Harrison, Dean’s Distinguished Professor of human nutrition at Ohio State University.

“Our results showed that those were inversely related to one another, meaning that the more we had the marker for garlic consumption, the less there was of the marker for the risk of cancer,” said Harrison, who is also an investigator with OSU’s Comprehensive Cancer Center and senior author of the study.

The scientists hope to find a nutritional intervention that could stop the process that develops these carcinogens.

The research began with a small human study based at Penn State University. Researchers there fed participants a weeklong diet lacking any nitrates or garlic. They then gave the participants a dose of sodium nitrate – in a formulation that would not become toxic, but which would show a marker in the urine of the potentially toxic process.

Groups were then treated with capsules containing varying levels of garlic: 1, 3 or 5 grams of fresh garlic, or 3 grams of an aged garlic extract. A separate group received 500 milligrams of ascorbic acid, or vitamin C. Both the nitrate formula and treatments were given for seven days. Urine samples were collected from all of the participants every other day for seven days.

That research team then turned to Harrison and colleagues, who explored the methods required to precisely quantify biomarkers in urine for both the garlic consumption and the presence of nitrosoproline, the indicator that nitrosation has occurred.

When the urine samples from the pilot garlic study were tested, it showed that the participants who had taken garlic had lower concentrations of the marker for nitrosation than did those who took no garlic. Though the differences were slight, the consumption of 5 grams of garlic per day was associated with the lowest level of the marker for potential carcinogens.

Vitamin C had a similar effect in lowering the marker for nitrosation.

Harrison noted that previous research has suggested that garlic and other plants with sulphur-containing compounds offer a variety of potential health benefits. Many questions remain about exactly what those benefits are and precisely how garlic works as a nutritional intervention.

“The precise mechanism by which garlic and other compounds affect nitrosation is under extensive investigation, but is not clear at this time,” he said.

“What this research does suggest, however, is that garlic may play some role in inhibiting formation of these nitrogen-based toxic substances. This was very small pilot study, so it’s also possible that the more garlic you have, the better it would be.”


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