Switching from conventionally grown to organic food could result in getting to 20 to 40 per cent more antioxidants, according to research published in the British Journal of Nutrition.
In addition, the study concluded, conventionally grown foods are three to four times more likely to contain pesticide residues, and twice as likely to contain cadmium, a toxic heavy metal contaminant.
The findings are based on a review of 343 studies comparing nutrient and pesticide levels in conventionally and organically grown fruits, vegetables and seeds. Research reviews like these are often undertaken to present a clearer aggregate picture of studies on a given topic.
The conclusion concerning antioxidants contrasts with reviews conducted by other researchers, published in 2009 and 2012. They found no significant differences in antioxidant content between conventional and organic produce. The authors of the new research review said that their finding is more reliable, because they analysed more studies and used more sophisticated means of analysis.
Although antioxidants aren’t nutrients that, like vitamins and minerals, have a recommended daily intake, they’re thought to prevent or delay some types of cell damage, and therefore theoretically can improve health and slow ageing.
In some cases, the researchers said, organic foods have 60 per cent more antioxidants than their conventionally grown version. In terms only of antioxidant intake, that’s the equivalent of eating an additional one or two servings of produce per day, the researchers said.
Organic plants were found to be lower in protein and amino acids than conventionally grown foods. “The nutritional significance/relevance of slightly lower protein and amino acid concentrations in organic crops to human health is likely to be low, as European and North American diets typically provide sufficient or even excessive amounts of proteins and essential amino acids,” the researchers wrote.
The researchers offered two theories for why organic foods might be higher in antioxidants.
First, it’s thought that plants produce the chemicals that form antioxidants in response to environmental stress, such as pests, disease and a relative lack of soil nutrients. Because conventionally grown foods are more shielded from these sources of stress, through pesticides and other growing practices, they don’t have as great an impetus to produce antioxidants, this theory goes.
Second, conventional farming uses fertiliser with a much higher nitrogen content, which leads to plants producing fewer antioxidants, the researchers speculated.
While the finding concerning antioxidants is potentially significant, it’s worth bearing in mind that the average American gets three servings of fruits and vegetables per day; the daily recommendation is five to 13 servings. If you’re not yet meeting the five-per-day recommended minimum, most nutritionists would agree the first step is upping your intake rather than focussing on how the produce is grown.