Should we only eat “organic” products?

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Market studies have shown that the most common reason why people buy organic products is the belief that they are healthy and safe. Other reasons such as that they are environment-friendly do not seem to carry as much weight with the consumers.

Are they healthy?

There is only indirect evidence on the health benefits of organic products. There is some evidence that protein quality is good, dry weight and fibre contents are favourable, mineral and vitamin concentrations high. There seem to be abundant levels of the phenolic secondary metabolites[1] such as flavonoids. Unfortunately there are no properly planned health studies which would have measured actual health benefits.

Several studies have shown higher concentrations of vitamin C, ascorbic acid in organic products, but there are also opposite results. The protein concentration is often lower than in conventional production, but the quality of protein is said to be better meaning relatively high concentrations of essential amino acids.[2] Since proteins are plentiful in the present diet, this would be meaningful perhaps only to an individual on a strict vegetarian diet. Milk fatty acid composition has been claimed to have superior quality, but this seems to be attributable to pasturing practices rather than to organic production as such.

Flavonoids are a group of compounds that are believed to be responsible for the generally accepted fact that plentiful consumption of fruit, berries and vegetables can decrease the risk of cancer. This has been associated with their antioxidant effects. Unfortunately there are some recent results that do not support this hypothesis, and the honest answer today is that we do not know why eating fruits etc. have these favourable effects.

Flavonoid concentrations depend on many different factors, including the climatic conditions of the summer and how ripe the products are when harvested. Therefore the higher flavonoid concentrations in organic products seem to depend, not only on the method of production, but also on the fact that organic products farmed close to the consumer are allowed to ripen better than mass produced products. For example, conventional tomatoes may be harvested while they are not quite ripe to allow for a longer shelf life. In some studies, no differences with conventional products have been detected, and in some studies they associate with damage caused by pests. Perhaps the high flavonoid concentration is also a sign of stress in the plant.

Hence there are two problems in any evaluation of the beneficial health effects. One is that many factors other than the farming method influence the properties thought to be beneficial, e.g. cultivar, soil properties, weather conditions of the summer, length of the growing period, ripeness at harvest, length and conditions of storage, and also what the consumer does with the product, including cooking habits and storage. Therefore it is not always clear if the differences between organic and conventional products are any greater than those between the same products harvested in different years.

Second, the secondary metabolites such as flavonoids and alkaloids are often substances of self-defence in plants; in principle they can be either beneficial or harmful depending on the substance. There is a huge variety of substances, but what regulates their formation is not clear – does it depend on either the method of production or pest activity is not known. In fact, it is even difficult to know, if the higher concentrations are beneficial or harmful.

With respect to the health benefits, one can only say that more studies of much better scientific quality are needed, before any clear conclusions can be drawn.

Are they safe?

The safety studies of organic products suffer from the same problems as the health benefit studies. Often there are no controls with which to compare the results. Just as the situation with the product content, the results of safety studies depend on many other factors as well as the production method. For instance, nitrate concentrations are influenced not only by fertilizer use but also by moisture, temperature, light conditions and cultivar. If harvesting is early, then the nitrate concentrations may be slightly elevated. Cadmium concentrations are influenced not only by whether fertilizers are being used but also by airborne cadmium deposition, soil quality, and plant species and cultivar.

Most studies have found lower nitrate concentrations in organic products than in conventional products. Even though the results are not unanimous, this difference is quite plausible, and it is also associated with the lower protein content of organic products. On the other hand, differences between plant species are far greater than the difference between organic and conventional products. For instance the nitrate concentration in Finnish organic red beet was 1100 mg/kg, in a conventional product it was 1600 mg/kg, and in an imported conventional product 1800 mg/kg. However, nitrate in all red beets was tens of times higher than the level in any potato. Thus a major factor defining your nitrate intake is the plant species that you consume.

Pesticide residues are generally lower in organic products as would be expected, but the differences between products from different countries are greater than the differences between organic and conventional products from the same country. This is because there can be more than tenfold differences in pesticide use per hectare within Europe. In low-pesticide countries such as Finland and Sweden, pesticide residues even in conventional products are usually below the detection sensitivity. On the other hand, in imported organic products, the Finnish Customs laboratory regularly detects some pesticide residues.

Heavy metal concentrations do not depend on the production method except for cadmium, if cadmium-containing phosphate fertilizers are used. Lead and mercury originate from atmospheric deposition. Their emissions have decreased in most countries and agricultural products are not important routes for these compounds.

Dioxins, furanes and PCB-compounds can be airborne pollutants, e.g. in Central Europe from old municipal waste incinerators polluting fields and pastures. Domestic animals then "vacuum-clean" these chemicals from pastures and they may also obtain some in their animal feed. Therefore concentrations in meat and dairy products were disturbingly high in the 1980s, but this is fortunately moving in a much better direction. There is no difference here between organic and conventional farming, but there may be remarkable differences between regions. In some cases, feeding animals outside may lead to higher concentrations; this was seen in some cases as high dioxin concentrations in organic eggs. The health effects have not been investigated, but it is unlikely that there are any major differences.

It is difficult to assess the state of organic farming, because there is a clear lack of good-quality research adhering to the acceptable criteria for scientific work. Despite this lack of evidence, organic products are a completely acceptable alternative but the basis should be a personal preference rather than a belief based on scientifically demonstrated benefits.

Notes and references

  1. Secondary metabolites are products of metabolism that are not common to all cells, but are produced specifically only by certain cells. An example of secondary metabolites is the flavonoids.
  2. Essential amino acids are a group of amino acids that the human body cannot synthesise. There are a total of twenty amino acids and the human body can synthesise only ten, but not histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, tyrosine and valine.

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