Organic tomatoes really are healthier than their conventionally grown counterparts, new research suggests.
Despite being smaller, they are packed with higher amounts of vitamin C and compounds that may combat chronic diseases, the findings show.
The reason for the difference is down to the organic plants' tough upbringing, it is claimed.
While conventionally grown tomatoes are pampered with pesticides and artificial fertilisers, organic farming forces the fruits to fend for themselves.
The stress they suffer as a result promotes greater concentrations of health-giving chemicals, according to the scientists.
Writing in the online journal Public Library of Science ONE, they argue that making life less easy for commercially grown fruits and vegetables can lead to improvements in quality.
Opinions are divided over whether organic farm products really are healthier and worth the extra money.
A US review of research studies published last year found that while organic fruits and vegetables may taste better, there is no evidence that their nutrition value is higher.
The Soil Association, which criticised the review, insists that organic farming is better for the environment and for health.
For the new study, scientists compared tomatoes grown on conventional and organic farms in Brazil. The farms were located within 1.5 kilometres of each other and shared similar natural environments.
Fruits from 30 plants in each farming system were sampled and analysed.
Tomatoes grown on organic farms were 40% smaller than those produced conventionally. However, their concentrations of vitamin C were up to 57% higher, and ripe fruits contained well over twice the quantity of phenolic compounds.
Plant phenols, such as flavonoids, are largely responsible for the health-giving properties attributed to many fruits and vegetables.
The organically grown tomatoes tested by the Brazilian researchers were fertilised with animal manure and vegetable compost, but not sprayed with pesticide.
In contrast conventionally grown tomatoes were treated with inorganic fertiliser and the pesticide FASTAC 100.
A stress-linked enzyme called phenylalanine ammonia lyase (PAL) was twice as active in the organic fruits.