It is well accepted by many experts that conventional farming practices may pollute waterways and leave greater pesticide residues on produce when compared with organic farming practices. Arguments for improved nutritional quality of produce from organic farming, however, have been highly controversial. The bulk of published scientific studies have found little difference in nutritional composition of conventional and organic produce. Despite numerous commentaries critiquing the shortcomings of these conclusions there remained little support for increased nutritional content of organic produce compared with conventional, until now. In June, 2014, the British Journal of Nutrition published a comprehensive review of all studies investigating the nutritional differences between organic and conventionally grown crops. In this review, the researchers concluded that the bulk of the scientific evidence now supports significant nutritive benefits from consuming organic produce.
Polyphenols, including flavonoids, flavones, flavonols, anthocyanins, and xanthophylls, were estimated to be 20-40% higher in organic produce compared with conventional produce. Polyphenols have been shown to be produced in plants during times of stress. It has been hypothesized that the increased levels of polyphenols may be the result of increased pest burden. Similarly, limiting nitrogen availability by restricting use of nitrogen fortified fertilizers in organic farming stresses a plant and is also associated with higher polyphenol content. While the use of pesticides and nitrogen-laden fertilizers may be responsible for the larger size and fewer blemishes seen in conventional crops, they may also be decreasing their nutritional value.
The results from vitamin and mineral content analyses, however, did not support a notable advantage from purchasing organic produce over conventional. While vitamin C content was slightly higher in organic produce, vitamin E content was slightly lower. Carotenoids levels (which includes measurement of beta carotene, a precursor to vitamin A) were only significantly higher in organic fruits, but not vegetables. There was no significant difference in vitamin B content. Levels of vitamin K have not been sufficiently investigated. Amounts of zinc and magnesium were only slightly greater in organic produce, about 5% greater. Levels for other important minerals, like iron and calcium, were not significantly greater in organic produce. However, the amount of cadmium, a potentially toxic metal, was significantly lower in organic produce, and is likely the only clinically meaningful difference in mineral content between organic and conventional produce. Cadmium is thought to be a contaminant in many chemical fertilizers used in conventional farming.
Conventional produce did perform superiorly to organic produce in several parameters. Protein content was 15% higher in conventional produce, likely due to use of nitrogen-fortified fertilizers, since nitrogen is an important building block of protein. This was primarily seen in grains. Additionally, fiber content was 8% higher and sugar content 7% lower in conventional produce. The reason for this difference is not known; however, it is likely small enough that it won’t provide a clinically significant difference among those consuming a primarily organic diet compared with those consuming a primarily conventional diet.
The success of this study in identifying significant nutritional advantages to organic crops compared with conventional crops is likely due to a more comprehensive inclusion of studies than prior reviews, as well as applying a weighted system of analysis based on the quality of the studies included. This recent review represents the most comprehensive and robust analysis of the data to date and, therefore, overshadows findings from previous reviews. While the nutritional content of organic foods is likely superior to conventional foods generally, nutritional content varies greatly with different farming practices. In no way do the results of this study suggest that overall fruit and vegetable consumption should be decreased if access to organic produce is limited. There are still significant health benefits from consuming conventional crops. Where possible, however, replace conventionally grown produce with organic produce to benefit from their lower amounts of pesticide residues and increased nutritional value.
By Ron Beckstrom, MS, RD, HFS
This article is for nutrition information purposes only and does not constitute medical advice. Always seek the advice of a qualified health provider with any health or nutrition concerns you may have. The information in this article is not intended to promote any specific product, or for the prevention or treatment of any disease.