Onion and garlic, extensively used in cooking as flavouring agents, seasonings, salad dressing and sauces, are rich in components which can prevent Deoxyribonucleic Acid (DNA) damage implicated in cancer causation, says the study by Kalpagam Polasa and Kamala Krishnaswamy of the National Institute of Nutrition (NIN) at Hyderabad.

Since a majority of cancers are likely to originate as a consequence of genetic mutations, protection against the genetic damage can be beneficial at late as well as early stages of cancer development.

The oils of garlic and onion, both from the same plant family `allium', can inhibit growth of a particular type of cancer in mice, the researchers found.

The anti-mutagenic effect was observed even at low levels of garlic consumption such as 500 milligrams per 100 grams of diet, they said.

The NIN study also showedboiling and frying did not alter the beneficial properties of these items.

Onion and garlic, widely used in traditional medicinal systems to treat a score of diseases, can also prevent heart blockage, ageing and have anti-microbial properties, the study added.

Garlic, acting as a double-edged sword, reduces the chances of atherosclerosis -- deposition of lipids in the inner walls of the arteries, thereby blocking the flow of blood in these conduits.

It reduces serum cholesterol level in the blood which enhances lipid deposition and increases the level of `good cholesterol' which scavenges lipids.

These two items can also reduce increased platelet activity, another factor associated with atherosclerosis, the study said.

Garlic is also found to scavenge free radicals -- the biological bullets that destroy tissue to accelerate ageing -- due to its rich content of sulphur-containing chemicals and thereby helps prevent ageing.

According to the study, the intake of alliums should continue for at leasttwo to three months because once discontinued, the lowered levels may start rising again.

Though adequate intake of these two items along with essential nutrients was useful in preventing diseases, these items were not substitutes for medicines, the researchers cautioned.