03 August 2009

Organic foods: a write-off, or not?

Newspaper headlines recently announced that organic foods are no healthier than conventional foods. But DietDoc says we shouldn't give up on these foods just yet.

Newspaper headlines recently announced that organic foods are no healthier than conventional foods (Reuters, 2009).

If you read these reports, you might have been shocked and disappointed that your belief in organic foods has been refuted. But what we have here is a classic example of the press blowing a research finding out of context.

Anyone with a scientific background, who is prepared to do some reading in the literature, will be able to view this seemingly final statement, that it's nonsense to eat organically grown food, in a more balanced light.

The present evidence
The much-quoted study by Dangour and his team at the London School of Hygiene and Tropical Medicine, reports on what is called a meta-analysis.

In such a study, the researchers don't do any experiments themselves, but search the scientific literature for articles published over a period of time (in this case, 50 years from 1 January 1958 to 1 January 2008), which have investigated the specific subject they're interested in (in this case, the differences in nutrient content between organically and conventionally produced foodstuffs).

When researchers have identified the articles that meet this requirement, they subject them to certain strict criteria. For example, they only use articles that have been published in reputable or peer-reviewed journals, or they only use articles that have a sound statistical basis. Studies that use too few subjects or samples are usually discarded.

By this process, Dangour et al (2009) reduced 52,471 potential articles down to 162 (137 dealt with crops and 25 with livestock products), of which 55 studies were classed as “of satisfactory quality”. The results reported for these 55 satisfactory studies were then subjected to further analysis.

The results of this analysis then led Dangour and coworkers (2009) to deduce that “Organic food is no healthier [than conventional food]”.

Other studies
Intrigued by this deduction, I also searched the literature to see what other researchers have recently been saying about the difference in conventionally grown and organically produced foods.

Worthington did a similar analysis in 1998 of studies covering a 50-year period and concluded:

  • “There is a trend in the data indicating higher nutrient content in organically grown crops”, which can possibly be explained by the fact that conventionally grown crops have a higher water content, which ‘dilutes’ the nutrients in these foods.
  • Organic crops had higher levels of vitamin C, lower levels of nitrate and an improved protein quality. This was also confirmed by reviews conducted by Wiliams in 2002 and Magkos and coworkers in 2006.
  • Animals fed organic feeds had improved growth and reproduction.

These other publications stated over and over again that we don't have enough evidence to draw conclusions about any potential differences that may or may not exist between organically and conventionally grown foods.

The other authors felt strongly that additional research was required and repeatedly said that further research is necessary to confirm the trends identified in the available data and to clarify the precise relationship between farming practices and the nutritional and other qualities of foods (Worthington, 1998).

No controlled intervention studies using human subjects have as yet been carried out (Williams, 2002). So, no experimental studies have looked at whether human subjects who were given either organic or conventional foodstuffs to eat for a specific period had improved biochemical markers of nutritional status (for example, higher vitamin and mineral levels in the blood).

Until such studies have been conducted, we won’t have a final answer. Bourn and Prescott (2002) point out that, “While it's likely that organically grown foods are lower in pesticide residues, there has been very little documentation of residue levels”.

It's clear that we need more good-quality research to investigate the nutritional, contaminant and microbiological differences between organically and conventional foodstuffs, and this means research at ground level (please excuse my unintended pun!), not at the meta-analysis level.

Unanswered questions
I, for one, would be interested to know if organically grown crops and meat, milk, eggs and cheeses from organically raised animals have different pesticide, herbicide, fertiliser, environmental contaminant, plant toxin, and pathogenic microorganism profiles than conventionally grown foodstuffs.

Another aspect that needs to be investigated is the question of taste and aroma. Are we kidding ourselves that organic products taste and smell so much better than standard products? Or does the use of compost instead of chemical fertilisers, pesticides, and herbicides improve the flavour and aroma of organic foods?

Conversely, we also need to know if organically grown foods are safe or if the fact that they are fertilised with mulch, compost and manure make them more susceptible to contamination with microorganisms.

As Magkos and his team (2006) point out, “Organic doesn't automatically equal safe”. Do crops that are not constantly being sprayed with pesticides develop fungal infections that can expose us to so-called mycotoxins, which have been linked to a variety of diseases such as cancer?

My conclusion is that the article published by Dangour et al (2009), classifying organic foods as no healthier than conventional foods, isn't the last word we'll be hearing on this subject. I agree that we need more hands-on, well-controlled research including human studies, if possible, into this fascinating subject to give us answers to all the questions that remain.

Because organically grown foods cost more than conventionally grown foods, it's understandable that the Food Standards Agency of the British Government, who commissioned the study conducted by Dangour and his team, will welcome their findings during the present recession that has the world in its grip. In this particular economic climate, no government wants its people to spend scarce money on anything except the basics.

I concur that if you're struggling to make ends meet financially, then this isn't the time to spend money on organic food that you cannot afford. The first principle is to put food on the table and, in a financial crisis, the least expensive, safe food must be our first choice.

But if the world recovers from its economic woes and you can afford organically grown foods, and if future research should produce different results to the ones that have torpedoed organically grown foods at the moment, then by all means buy and enjoy your organic foods. They certainly look, smell and taste better than conventional produce.

(Dr I.V. van Heerden, DietDoc, August 2009)

Any questions? Ask DietDoc

(Bourn D, Prescott J (2002). A comparison of the nutritional value, sensory qualities, & food safety of organically & conventionally produced foods. Crit Rev Food Sci Nutr, Vol 42(1):1-34; Dangour AD et al (2009). Nutritional quality of organic foods: a systematic review. American Journal of Clinical Nutrition, doi.10.3945/ajcn.2009.28041 published ahead of print; Magkos F et al. (2006). Organic food: buying more safety or just peace of mind? A critical review of the literature. Crit Rev Food Sci Nutr, Nol 46(1):23-56; Reuters (2009). Organic food is no healthier, study finds. published on on 29/07/2009; Williams CM (2002). Nutritional quality of organic food: shades of grey or shades of green? Proc Nutr Soc, Vol 61(1):19-24; Worthington V (1998). Effect of agricultural methods on nutritional quality: a comparison of organic with conventional crops. Altern Ther Health Med, Vol 4(1):58-69.)


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