A recent survey (Feb 2009) of prices at a local supermarket showed that organic tomatoes cost 84% more than non-organic equivalents, but they contain 79% more quercetin and 97% more kaempferol, so for these two antioxidants, associated with improvements in human health and well being, the purchasing power is the same. Since organic food is also free from chemical agents (e.g. pesticides) which generate free radicals, you need less antioxidant to ward off the oxidative damage done by these additives, which on balance makes organic food cheaper and healthier than conventional foods.
Institute of Food Science and Technology - Organic food - Information statement.
This statement replaces the version dated February 2005. To summarise:
1. Organic food is likely to contain lower levels of agricultural chemicals.
2. Organic food, like non organic food is likely to be contaminated by pathogens and should be washed thoroughly, especially uncooked food, before eating.
3. No significant nutritional or health difference was found between organic and conventionally grown food.
At this website, we accept sections 1 and 2, but 3 is unacceptable because those organic foods rigourously and scientifically tested against comparable non organic foods have been found to contain higher levels of antioxidants, therefore more research is needed.
It is now possible to differentiate between organic and conventionally-grown foods in terms of their antioxidant content if the experiments are rigorously controlled. Dr Alyson Mitchell of the Department of Food Science and Technology, Unversity of California, Davis explained that the standardisation of soil fertility, environment and crop management was studied over a ten year period, during which samples of conventional and organically-grown tomatoes were archived. The work published in J. Agric. Food Chem. 55 (15), 6154-6159, 2007 found 79% and 97% increases in quercetin and kaempferol respectively in organic tomatoes when compared with conventionally-grown fruit.
There are one or two earlier reports showing improvements in antioxidant concentrations in peaches and apple puree, and in the vitamin C, beta-catotene and flavonoid content of tomatoes.
As the work is published it will be summarised and referenced here.
Juice from organically-grown grapes was significantly higher in total polyphenols than conventionally-grown grape juices, and red juices were higher than white juices. In general, the measured anthocyanins, catechins and procyanidins all showed increased amounts in the organically-grown juice, but notably, epicatechin and B4 procyanidin levels were significantly lower in the organic sample
C.Dani et al., Food Chem. Toxicol. 45 (12), 2574-2580, 2007
Significant increases in the polyphenol content of organic peaches compared to conventionally grown fruit was reported by Carbonaro and Mattera in 2001. Less convincing evidence for pears was also reported.
M.Carbonaro and M. Mattera, Food Chem., 72 (4) 419-424, 2001.
Cherry tomatoes grown by irrigating the plants with diluted sea water produced fruit with a higher nutritional value (Vitamin C, E, dihydrolipoic acid and chlorogenic acid) than the control, thought to be due to the production of various antioxidants in response to salinity-induced oxidative stress. Although this is not an organic experiment, it demonstrates the principle of stress induced enhancement of antioxidant content.
C.Sgherri et al., J. Agric. Food Chem., 56 (9) 3391-3397, 2008
The Sunday Times, 28 October 2007, ran a front page story, in competition with a Royal sex and drugs blackmail story, claiming that an official study has definitely shown that organic fruits and vegetables are richer in antioxidants than conventionally-grown products. Certainly, the £12m four-year project, co-ordinated by Professor C. Leifert found up to 40% more antioxidants in certain organic foods compared to conventionally-grown produce. The full article on page 11 summarised the results of this significant QualityLowInputFood (QLIF) project. It is welcomed particularly because, being an EU funded experiment, in which Newcastle University subscribed results obtained from its 725 acre split organic/conventional farm, the FSA cannot now brush these results aside. However, as the FSA avers, the therapeutic benefits of specific antioxidants still have to be proven. And there are other ways of increasing antioxidant input. What is not in doubt from epidemiological evidence is that eating plenty of fruit, vegetables, nuts and grains is associated with human well being. The publication of the scientific results, after peer review, is expected over the next 12 months. In the meantime, limited data are available from other sources.
Organic versus conventionally grown plant foods – antioxidant content
At one time farmers grew nothing else but organic plant foods and animal feeds. It was only quite recently in the history of agriculture that artificial fertilisers, chemical stimulants and plant protectants have been introduced. The 1939-45 wartime population were fed a limited organically-grown food supply, but care was taken to ensure that the essential vitamins, minerals and nutrients were present through orange juice, fish liver oil and malt supplements. In general, the nation was healthy - and slim.
The present “epidemic” of obesity may in part be attributed to the change to non-organic farming methods. The thesis is that plants protected by chemical “cosh” sprays have no need to produce natural defences against pathogens and browsing fauna. Strangely, the plant’s chemical defences are drawn from the arsenal of astringent and bitter tasting vegetable tannin (polyphenol) antioxidants. When insect attack occurs, the plant mobilises polyphenols to accumulate around the wound, thus deterring the insect or animal from further feeding at that site. These same compounds may well provide protection against pathogens and toxic invaders for human consumers who are not put off by the bitterness.
Although the Minister of Agriculture recently declared that there was no essential nutritional difference between conventional and organic food crops, he was referring to the proximate analyses of foods, which of course are comprised of water, carbohydrate, protein and fat. And for these major components, there may not be any great difference.
Evidence is accumulating in support of the fact that organically grown plants contain more vitamins and antioxidants than the non-organically grown control plants. These are minor or trace components in foods and therefore the analytical precision has to be orders of magnitude greater to measure the difference between organic and conventional foods. Recent careful experimental work at the University of Newcastle (UK) has found up to 30% more total antioxidants in the organic crop and at the University of California (USA), 79% and 97% more quercetin and kaempferol respectively, were found in organic tomatoes. These experiments compared plots with the same soil type, husbandry, treatments and climatic growing conditions in the same season. Other experiments, especially ones where samples of organic and non-organic foods are purchased at a supermarket, generally produce inconclusive results through the lack of a comparative production provenance. There are one or two other well-constructed scientific studies that have found reliable differences with statistically higher amounts present in the samples of organic foods e.g., grapes and peaches.
In summary, it is mandatory that all the essential parameters controlling the two experimental plots are equivalent. Reliable data are beginning to appear in the scientific press. Organic crops must provide their own defences against predator attack, which is a good scientific reason why they should contain more antioxidants than the equivalent conventionally grown products. These substances are the vegetable tannins (polyphenol proanthocyanidins and proanthocyanin glycosides) and flavanol monomers, all classed as antioxidants. For organic seed production, plants also need to attract symbiotic species for fertilisation and seed dispersion. These are the coloured anthocyanins and carotenoids, also classed as antioxidants.
The future looks bright. The future looks rosy. It must be the presence of more carotenoid and anthocyanin antioxidants in our organic foods!
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In January 2007, the environment secretary, David Milliband said, "There is no evidence that organic food is better for you than conventionally-grown food"
(BBC News) Although no differences could be found when proximate analyses of the major nutrients, fat, carbohydrate and protein were performed, evidence that trace nutrients, such as antioxidants, are significantly higher in organic foods is orders of magnitude more difficult to verify, but is beginning to appear in the scientific press.
Some antioxidants, e.g. the bitter-tasting polyphenols, as explained in the Introduction are mobilised by the plant under stress as natural chemical deterrants to predators. Thus it would not be surprising if organically-grown food crops are shown to have higher concentrations of antioxidants, simply to survive in a hostile, but more natural environment. If antioxidants are found to be the therapeutic agents then organic foods will be healthier than conventionally grown produce.