Chopping them may make you cry, but onions may also improve your memory, scientists said today.
Researchers at Hokkaido Tokai University in Japan found people suffering from memory loss who ate the layered vegetable found it improved their ability to recall.
Experts said the findings could be important in the fight against brain diseases such as Alzheimer's and Parkinson's.
The researchers discovered an antioxidant found in onions binds with harmful toxins in the brain and flushes them out of the body.
The compound, which contains sulphur, is found in many members of the allum family, including garlic.
Food expert Ian Marber said: "Onions are one of the richest and most readily available sources of sulphur-containing compounds which have been shown to slow down the deterioration of memory usually associated with ageing.
"Onion extract has also been shown to maintain the hippocampus, a part of the brain that is involved in processing emotions as well as memory.''
But he warned onions that are over-cooked may lose their memory-helping properties. They should instead be cooked on a low heat.
The research compounds onions' reputation as being good for your memory.
A recent French study found a high flavonoid intake can reduce memory loss associated with ageing. Onions contain a flavonoid called quercetin, and in greater quantities than in tea and apples.
Other evidence credits onions with success at combatting the common cold, hayfever and heart disease.