Wednesday, May 26, 1999 Published at 18:13 GMT 19:13 UK
Raw garlic tackles cancer
Previous studies suggested a massive amount of garlic was needed
Doctors have suggested how much garlic they think a person would have to eat each day to gain from its anti-cancer properties - half a clove.
It should be served raw to have maximum effect, they said.
Previous studies had suggested that a human would have to eat their own weight in garlic before gaining any benefits.
But the new research suggests half a raw clove would be enough, rising to four and half cloves if cooked.
Although garlic is best known for its ability to stave off heart disease, scientists have also been examining its role in cancer.
They suspect it can counter the effects of particles that cause bowel cancer, but want to know which parts of the plant are actively involved in the process.
Rex and Christine Munday, a husband and wife research team based in New Zealand, were looking at what is thought to be one of the key ingredients - a substance called diallyl disulfide.
It causes the gut to produce enzymes that can clear it of cancer-causing particles.
Their findings are reported in New Scientist magazine and will be published in the journal Nutrition and Cancer.
The two of them gave rats varying doses of disulfide, and found that it increased levels of the enzyme by up to 60% when given in amounts equivalent to a moderate daily intake in humans.
"It's been recognised that garlic is an inducer of these enzymes, but previous studies have all been with doses at meaningless levels," Rex Munday told the magazine.
"They implied you'd need to eat your own weight in garlic to achieve beneficial effects."
Instead, the Mundays found that in rats the benefits kicked in at between 0.075mg and 0.3mg of disulfide per kilogram of body weight, or half a clove of garlic for the average human.
'Larger study needed'
Lesley Walker, head of science information at the Cancer Research Campaign, said: "It's an interesting study, but people shouldn't get too excited about it."
This was because the research was performed on rats and did not look specifically at bowel cancer, but at a substance that can reduce the risk of bowel cancer.
She said it would take a much a larger study to prove any benefits, but there was no harm in eating plenty of garlic as eating plenty of fruit and vegetables reduces the risk of cancer.
"It's lovely to think that eating half a clove of garlic reduces the risk of bowel cancer, and if you like garlic then go for it - but don't necesssarily be surprised if you then develop cancer."
Diallyl disulfide was first proven to have the ability to slow the growth of bowel cancer in 1995.
Dr Sujatha Sundaram, a researcher at Pennsylvania State University, found that it caused human bowel cancer tumour cells to shrink and die when transplanted into mice.
Dr Sundaram was also responsible for finding another compound found in garlic that slowed the growth of breast cancer in rats.