“Natural tomatoes are packed with more disease-fighting antioxidants,” the Daily Mail has reported, going on to say that “it really may pay off to fork out for the more expensive organic produce”.
This news is based on research comparing the amount of chemicals called polyphenols in organic versus non-organic tomatoes. Polyphenols are produced as tomatoes ripen, and the amount of polyphenols tomatoes produce can be affected by growing conditions. Polyphenols are considered to be antioxidants, and it has been suggested that consuming foods high in antioxidants may be good for your health. The researchers thought that because organic tomatoes ripen for longer as they are grown in less nitrogen-rich soil they would contain higher levels of polyphenols.
When the researchers compared the chemical profile of the two types of tomatoes, they found – as expected - that the organic tomatoes contained higher levels of polyphenols than the non-organic tomatoes.
This study suggests that some organic tomatoes contain higher levels of chemicals called polyphenols than “conventionally grown” tomatoes. It does not, however, tell us whether eating organic tomatoes will provide any additional health benefits over eating conventional tomatoes. Nobody ate the tomatoes, so no health outcomes could be measured.
Where did the story come from?
The study was carried out by researchers from the University of Barcelona and the Institute of Health in Spain. The research was funded by the Spanish Ministry of Science and Innovation, and other Spanish foundations. It is worth noting that Spain is one of the leading producers of tomatoes.
The study was published in the peer-reviewed Journal of Agricultural and Food Chemistry.
The Daily Mail explained the research well. However, the Mail focused on the premise that eating antioxidant-rich foods may be beneficial for health, while not mentioning any of the research that has found contradictory results.
What kind of research was this?
This was a laboratory study. It compared the amount of polyphenol, a type of antioxidant, in organically grown tomatoes to that in “conventionally grown” tomatoes. The researchers report that the amount of polyphenols present in a plant or fruit is affected by growing conditions, including the amount of nutrients in the soil. Polyphenols are produced in plants in part as a response to “stress conditions”, such as a shortage of available nutrients. As conventional farming techniques tend to include the use of pesticides and fertilisers high in nitrogen, the researchers thought that the polyphenol content of the tomatoes would be lower than that seen in organically grown plants, which are grown under more stressful conditions.
There is quite a bit of research into the role of antioxidant-rich foods and human health. Research has looked into their role at fighting heart disease and cancer - with some contradictory results. While this study is related to such research, it can only tell us about the composition of one particular variety of tomato grown in various conditions. It cannot tell us whether higher polyphenol or antioxidant content will be more beneficial to the health of people who eat organic produce.
What did the research involve?
The researchers purchased raw organic and conventionally grown Daniella tomatoes from markets throughout Barcelona in 2010 and 2011. All of the tomatoes were at a similar stage of ripeness, and were of a similar size. The researchers wanted to examine the properties of raw tomatoes as previous research into their polyphenol content had been done in ketchups and juices.
They then blended the tomatoes to form a paste, and analysed the samples for the presence of several types of polyphenols: flavonols, flavanones, flavones and hydroxycinnamic acids. They then compared the levels of each of these elements between the two types of tomatoes.
What were the basic results?
The researchers found that organically produced tomatoes contained higher levels of many of the polyphenols. However, the degree of difference in the levels varied across different types of polyphenols. Specifically, the researchers found that:
- Flavones including phenolic and hydroxycinnamoylquinic acids were found in higher concentrations in organic tomatoes than non-organic tomatoes. However, differences in the concentration of the flavone apigenin, which is thought to have anti-inflammatory properties, were smaller than those seen in other flavone concentrations.
- Flavanones, such as naringenin, occurred in higher concentrations in organic tomatoes than in conventionally grown tomatoes.
- Flavonols including rutin and quercetin were found in higher concentration in organic tomatoes than non-organic tomatoes.
Overall, the researchers found that the method of production (organic versus conventional) affected the nutrient content of the tomatoes, with organic tomatoes having a higher concentration of polyphenols than conventional tomatoes.
How did the researchers interpret the results?
The researchers concluded that production methods affect the nutrient content of raw tomatoes, with organic tomatoes displaying higher concentrations of polyphenols than the conventionally grown tomatoes. They say, “A number of studies have addressed the question of whether agricultural chemicals and other agricultural methods including organic farming affect nutrient content. The question is still unresolved”.
This study suggests that organically grown tomatoes contain higher levels of polyphenols than conventionally grown tomatoes. Whether or not this translates into additional health benefit over non-organic tomatoes is not clear, although the researchers make this assumption in their conclusion.
This study does not tell us whether eating organic tomatoes is more beneficial to our health than eating conventionally grown tomatoes. The researchers say that, based on their findings, “vegetable and fruit products grown in organic agriculture would be expected to be more health-promoting than those produced conventionally”. However, this interpretation does not address the contradictory evidence concerning the health benefits of consuming organic versus non-organic foods, and further studies of how people are affected by their diet would be needed to confirm the interpretation.
Research into antioxidants in food is complicated by the fact that there are many antioxidant and some ‘pro-oxidant’ chemicals found in the same food. Also, more than one antioxidant may be found in a single foodstuff. For example, tomatoes contain both vitamin C and lycopene, which gives red fruit their colour and may also be an antioxidant. Which of the potentially ‘bio-active’ chemicals are important to human health remains uncertain.
Overall, this research tells us more about the effect of farming techniques on a tomato’s nutrient content than it tells us about the effect of a tomato’s nutrient content on our health. However, the field is ripe for someone to conduct controlled trials looking at health outcomes for people.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on twitter.