Organic agriculture largely excludes synthetic inputs - pesticides, herbicides and fertilisers and focuses instead on long-term ecological health. The health benefits of organic foods have now been highlighted by new research: they are richer in anti-cancer chemicals. Prof. Joe Cummins reports.
Plant phenolics (flavonoids) are plant secondary metabolites (mainly pigments and flavor compounds or their by-products) that are believed to protect the plant against insect predation, bacterial and fungal infection and photo-oxidation. This same class of plant chemicals has been found to be effective in preventing cancer and heart disease, and to combat age-related neurological dysfunctions.
The main target of these plant chemicals is to protect the cell against damage caused by active oxygen radicals. Oxygen radicals are generated from exposure to oxygen that has in turn been activated by exposure to radiation, heavy metal ions and chemicals. Oxygen radicals cause cancer by damaging DNA, resulting in mutations; by activating protein kinase enzymes involved in signal cascades that regulate cell growth; and by promoting angiogenesis (invasion of blood vessels into tumours to allow rapid growth of the tumour). Oxygen radicals are also implicated in cardiovascular disease and in age-related nerve cell damage.
Conventional agriculture depends on heavy applications of chemical fertilisers, frequent spraying with chemical pesticides and irrigation. Such practices are believed to inhibit the production of flavonoids. On the contrary, organic agriculture, which eliminates the use of synthetic pesticides and chemical fertilizers, creates conditions favourable to the production of health-enhancing plant flavonoids.
Recent research has been carried out comparing conventional with organic and sustainable production of berries and corn . (Sustainable designates the use of farm practices that are environmentally-sound.) The research showed that the plant phenolics were significantly elevated in organic and sustainable produce in comparison with conventional production.
An earlier review of studies comparing organic and conventionally grown foods did not examine plant phenolics; but found that the conventionally produced foods had higher levels of nitrates and synthetic pesticides and relatively less total solids than organic foods. Animals preferred organic foods while human preferences were less clear .
A new report by Asami and coworkers  provides a long list of studies documenting the health-enhancing attributes of plant phenolics and a few key reviews are highlighted as follows.
Colic and Pavelic  reviewed the molecular mechanisms underlying the anti-cancer properties of natural dietary plant phenolics. They showed that the natural compounds had multiple functions. For example, they modulate signal-transduction cascades, and show both cytostatic (inhibiting cell growth) and cytotoxic (cell-killing) activities towards cancer cells.
McCarty  reviewed current prospects for controlling cancer growth with nutrients and plant chemicals and suggested that combinations of plant chemicals would enhance cure rates with standard therapies.
Ross and Kasum  listed studies that support a protective effect of flavonoids in cardiovascular disease and cancer but indicated that other studies showed no effect and a few studies suggested potential harm.
Youdim and Joseph  pointed out that long-term oxidative stress contributes to nerve degradation and age-related diseases of the nervous system such as Parkinsons disease and Alzheimers disease; and that there is an emerging role for plant chemicals in combating age-related neurological dysfunction.
A very large body of evidence thus suggests that plant phenolics, clearly present in higher concentrations in organic than conventional foods, are effective in the fight against cancer, heart disease and age-related neurological dysfunction. Furthermore, there is increasing evidence that organic agriculture gives high yields, and is more beneficial to the environment and more sustainable [e.g. 7].
All this evidence is largely denied or ignored by advocates of genetically modified foods.
Article first published 27/03/03
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