Scientists say there may be more truth in the old wives tale that an apple a day keeps the doctor away, than was initially credited.
Researchers who examined the chemical content of eight different varieties of the fruit to compare the potential health benefits discovered some contained far higher levels of disease-busting antioxidants than others.
The Red Delicious apple was found to have the highest concentrations of polyphenols, a type of antioxidant, while the Empire variety had the lowest.
After discovering the skin of the apple contains five times more polyphenols than the flesh, the scientists recommend not peeling the fruit.
Their findings could encourage growers to develop a 'super breed' of hybrid apple which packs a healthier punch.
According to Professor Rong Tsao, who led the research team for the Agriculture and Agri-Food department in Guelph, Ontario, when taste and texture do not matter, choosing an apple with a high proportion of polyphenols in the flesh and skin can produce more health benefits.
Antioxidants help the body fight cancer, heart disease, Alzheimer's, high blood pressure and other conditions usually associated with the ageing process.
By curbing oxidation in the body, antioxidants help prevent cell and tissue damage, and can also lower cholesterol.
Another study found that rats fed the human equivalent of up to six apples a day for six weeks were 44 per cent less likely to develop breast tumours.
Prior to this study scientists had been unclear about which polyphenols were the most active in apples.
Professor Tsao and his colleagues used three laboratory measures to evaluate polyphenol activity in Red Delicious, McIntosh, Cortland, Northern Spy, Ida Red, Golden Delicious, Mutsu and Empire varieties.
They discovered that two polyphenols, epicatechin and procyanidin B2, were the greatest contributors to antioxidant activity and Red Delicious had twice as much polyphenol activity as Empires.
The study is published in the Journal of Agricultural and Food Chemistry.