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Organic food is no healthier than conventional food PDF Print Email

It has been reported that organic vegetables are no healthier than food grown conventionally.


A scientific study has grown vegetables under both organic and conventional conditions and has found no difference to the levels of polyphenol compounds they contained.  There have been some claims that polyphenol antioxidants may reduce the risk of some cancers, dementia and cardiovascular disease. However, their effects have only been observed in studies of cells, and their health benefits in humans have yet to be confirmed. In this study, the levels of polyphenols in the crops were the same, regardless of whether they were grown with organic methods or using pesticides and non-organic fertilisers. This research suggests that organic farming methods do not increase the amount of polyphenol antioxidants, however, the decision to eat organic produce may be a lifestyle one for many people, influenced by factors such as taste and preferring farming methods that do not use pesticides. Fruit and vegetables have numerous health benefits far beyond their antioxidant content and, whether organic or not, it is important to try to eat at least five portions every day.


The research set out to examine whether the nutritional content of potatoes, carrots and onions was affected by how they are grown. The researchers specifically looked at polyphenol antioxidant compounds such as flavonoids and phenolic acids. They also set out to establish whether the concentrations of these compounds varied in different soil, locations and the years in which  the crops were grown. The study only looked at how farming methods affect the crops, and did not involve research into how animals or people absorb nutrients from food, or what impact this might have on health. It did not investigate broader health benefits of consuming fruit and vegetables grown by different methods, as polyphenol antioxidants are only one aspect of nutrition, and the health benefits of consuming them are not fully understood.


The researchers grew potatoes in a crop rotation experiment in three different locations from 2007 to 2008. Carrots and onions were grown at one location as part of another crop rotation experiment. Both experiments grew the crops under three systems: one ‘conventional’ (using pesticides and non-organic fertiliser) and two organic systems without pesticides (both using animal manure, but one also adding ‘cover crops’, which are used to improve soil fertility). Comparisons in nutritional content of the vegetables were made by harvesting on the same day in all farming systems, and a 15kg sample of each vegetable crop was analysed. Slices were taken from these, then processed and preserved by dry-freezing. The samples were analysed in a laboratory to determine the levels of flavonoids in onions and phenolic acids in potatoes and carrots.


Levels of flavonoids in onions were not found to vary between the different farming systems, although within each farming system there were variations in the levels of all the flavonoids measured. Within each system, there was some year-to-year variation in the levels of one of the flavonoids in onions. This may have been due to different weather conditions in each of the study years.The researchers made sure they took samples grown near each other to reduce any possible effect of microclimate or differences in soil fertility. The farming methods used also made no difference to the overall levels of phenolic acid found in carrots. However, within each system, carrots showed a greater variation in phenolic acid levels than the potatoes did. In the potatoes, levels of one phenolic acid (5-CQA) were found to be higher in the organic system using cover crops than in the conventional system.


The researchers found “no significant differences in the content of flavonoids and phenolic acids between the conventional and the two organic growth systems”. They speculated that the higher levels of one phenolic acid in potatoes in the second organic system may be due to them being grown on a different farm.

Their conclusions were that levels of synthesis of the compounds analysed did not vary dependening on growth conditions, the year the crops were grown or location.



This research suggests that organic farming methods do not affect the concentration of polyphenol antioxidants in a range of vegetables when compared with other farming methods. However, it is worth highlighting that the study did not assess other aspects of the nutritional composition of crops or  look at whether eating organic fruit and vegetables had any other health benefits. The specific benefits of polyphenol antioxidants are not fully understood, and only account for one of the numerous nutritional benefits from eating fruit and vegetables. With this in mind the study does not definitively answer the question of whether or not organically grown produce has different health benefits to crops grown by other farming methods or is better for your health.



Søltoft M, Nielsen J, Holst Laursen K Knuthsen et al. Effects of Organic and Conventional Growth Systems on the Content of Flavonoids in Onions and Phenolic Acids in Carrots and Potatoes. Journal of Agricultural and Food Chemistry, 2010, 58 (19), pp 10323–10329