A recent meta-study has found organic crops contain significantly more antioxidants than conventional crops, but how is that relevant for public health? For some leading British scientists it isn't, and they claim that to link phenolics with health benefits like cancer prevention is misleading. At www.freshfruitportal.com we take a look at comments by four experts published by the U.K.'s Science Media Centre, who question whether organic food actually is better for your diet, and if the category's higher prices would be worth the extra benefit even if it were.
Comparing organic to conventional crops is a tricky business and one that has been hotly-debated, according to St George's Hospital NHS Trust principal dietitian Catherine Collins.
"One of the key problems facing researchers in this field over the years is how to compare, well, apples and pears. Do you buy them at the supermarket and measure the difference in plant substances found in each type of produce at ‘point-of-sale?" she asks.
"Or do you choose two farms close to each other, one to grow organic and one to grow non-organic produce, and compare the two as picked? This removes the natural variation in soil richness as an influence of plant content.
"Or should you rely on formal experiments with sample crops? All these methods are valid but each generate very different answers depending on soil type, use of permitted plant additives to each type of produce, storage methods and time from farm to fork."
She says these complicated questions are what lead to such a big range of values for different plant substances in a large review such as that led by Newcastle University recently.
"For example, the antioxidant chlorogenic acid was sometimes lower and sometimes higher in organic foods when compared to non-organic varieties.
Collins highlighted the study showed flavanones and flavonols were higher in organic produce than non-organic versions, as were antioxidant anthocyanins, but questioned whether it was worth paying for the extra boost in these specific antioxidants.
"When you compare the price and availability of the organic version of foods rich in these antioxidants, paying double for organic didn’t provide you with double the antioxidant benefits – but it does reduce the amount of money left to spend on the rest of your diet," she said.
"As a dietitian I'd suggest forget the big 'O' title, and just enjoy your morning coffee or a juicy peach as a between meal snack as a rich source of this particular antioxidant, without the worry of how it was grown."
Also analyzing how the study conducted, Dr. Alan Dangour said it was surprising that the authors of the report decided to include all the data that they found, irrespective of their quality.
"In fact the study authors themselves note that there are significant concerns with the consistency and reliability of some of their findings," said Dangour, who is a reader in food and nutrition for global health at the London School of Hygiene & Tropical Medicine.
"Mixing good quality data with bad quality data in this way is highly problematic and significantly weakens confidence in the findings of the current analysis.
"It is a shame that greater care was not taken in trying to ensure that the analyses were based only on reliable and scientifically robust data from satisfactory quality studies."
Antioxidant health links "worryingly overstated"
Dangour also mentioned a concern raised by two other scientists at the Science Media Center, that people ought not automatically connect antioxidants with health benefits as if it were a given.
"Furthermore, the public health significance of the reported findings have been worryingly overstated," Dangour said.
"There is no good evidence to suggest that slightly greater antioxidant or polyphenolic intake in the human diet has important public health benefits, and there is no robust evidence to support the claim that consumption of greater amounts of these compounds reduces the risk of chronic diseases such as cardiovascular disease and cancer in human populations.
"All natural products vary in their composition for a wide variety of reasons. This paper provides no convincing evidence to refute our earlier finding1, fully supported by a recent US-led systematic review, that there are no important differences in nutrient content between organically and conventionally produced foods."
Dangour's stance was echoed by Professor Tom Sanders, who heads up the diabetes and nutritional sciences division at the King's College London School of Medicine, and Institute of Food Research (IFR) food and health programme leader Professor Richard Mithen.
"The article misleadingly suggest health benefits result from a high consumption of antioxidants particularly cancer protection," Sanders said.
"While the World Cancer Research Foundation in its systematic reviews concluded there is a relationship between fruit and vegetable consumption and a lower risk of cancer, they did state that there was insufficient evidence to make any claim for antioxidants and plant phenolics.
"Of greater significance is that there is no evidence provided that the relatively modest differences in the levels of some of these compounds would have any consequences (good or bad) on public health," Mithen added.
Mithen said the references to 'antioxidants' and 'antioxidant activity' suggested a poor knowledge of the current understanding within the nutrition community about how fruits and vegetables may maintain and improve health; an issue covered by Sanders as well.
"This article is misleading because it refers to antioxidants in plants as if they were a class of essential nutrients, which they are not," Sanders said.
"The compounds referred to are mainly plant phenolics and are produced in higher quantities when plants are environmentally stressed. Plant phenolics have both toxic as well as potential beneficial effects.
"Some vitamins have anti-oxidant properties such as vitamin E, vitamin C and beta-carotene but the differences between organic and conventional produce are trivial."
Mithen also questioned why antioxidants were mentioned by the authors to promote organics, while other aspects of organic production were not in the spotlight. Like Collins, he also raised the matter of affordability.
"This paper provides some evidence that under organic agronomic regimes, there may be an increase in the concentration of certain phenolic compounds in some fruits and vegetables," Mithen said.
"The paper also reports a decrease in protein, nitrates and fibre in the organically grown crops, which may be undesirable, and which are maybe unsurprisingly not referred to by the authors in their advocacy of organically grown produce.
"The additional cost of organic vegetables to the consumer and the likely reduced consumption would easily offset any marginal increase in nutritional properties, even if they did occur, which I doubt. To improve public health we need to encourage people to eat more fruit and vegetables, regardless of how they are produced."